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Severe thunderstorms will be possible across parts of western Montana, mainly Thursday afternoon and evening. Locally damaging winds may also occur across parts of New England, the Upper Midwest, and the Mid-Atlantic.
← back to overviewSPC AC 160518
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1218 AM CDT Thu Jul 16 2026
Valid 161200Z - 171200Z
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF WESTERN MONTANA
### SUMMARY
Severe thunderstorms will be possible across parts of western Montana, mainly Thursday afternoon and evening. Locally damaging winds may also occur across parts of New England, the Upper Midwest, and the Mid-Atlantic.
Northern Rockies
An upper low will skim the Pacific Northwest coast as it lifts northward through the period. Meanwhile, upper ridging will persist across much of the Rockies to the Plains. Wedged between the upper low and the western periphery of the upper ridging, a belt of enhanced south/southwesterly deep-layer flow will overspread the northern Rockies. Easterly low-level flow will transport 50s F dewpoints across region beneath steep midlevel lapse rates. This will support moderate destabilization (1000-2000 J/kg MLCAPE). Scattered thunderstorms will develop during the afternoon. Vertically veering wind profiles and increasing flow aloft will result in 30+ kt effective shear magnitudes. Organized cells will pose a risk for strong wind gusts and hail across much of the region. The greatest risk for 1+ inch hail will be across portions of western MT.
New England
A vigorous upper shortwave trough will move across the region through evening. Strong west/northwest deep-layer flow is evident in forecast soundings, with 40+ kt effective shear magnitudes likely. Boundary layer moisture will be somewhat muted compared to the previous few days, with dewpoints generally in the 50s F. Stronger heating is expected to the north of the more prominent smoke plume across southern New England, aiding in steepening low-level lapse rates. While instability will remain modest, strong flow and steep low-level lapse rates may support isolated strong/locally damaging wind gusts as convection spreads southeast from Quebec and across portions of northern New England through the afternoon.
Southern PA/Mid-Atlantic vicinity
Strong mid/upper-level flow will overspread the region on the southern periphery of the upper shortwave trough moving across New England. A surface front is expected to drop southward through the day, approaching the PA/MD border vicinity by late afternoon. Rich boundary layer moisture will be in place ahead of the surface front and beneath steep midlevel lapse rates. This will foster a corridor of 2000+ J/kg MLCAPE. Furthermore, forecast soundings show 30-40 kt effective shear magnitudes and steep low-level lapse rates. This environment generally should support organized cells/line segments. However, convective coverage is uncertain given stronger forcing for ascent focused north of the area. Additionally, it is uncertain if smoke will continue to have a deleterious impact on an otherwise favorable severe storm environment. Given conditional potential for at least locally damaging gusts, have included low severe wind probabilities.
ND/MN
A series of convectively enhanced vorticity maxima will migrate across the Canadian Prairies atop the upper ridge and through northwesterly flow aloft into parts of ND and northern MN this afternoon into tonight. At the surface, a weak low and surface front will move across ND into northern MN during the evening and overnight hours. South/southeasterly low-level flow will maintain a moisture-rich boundary layer, supporting a corridor of modest destabilization. Forecast soundings show supercell wind profiles, but also increasing capping through the late afternoon/evening. Nevertheless, most guidance develops convection across southern Manitoba into northeast ND during the evening, spreading east/southeast across northern MN during the nighttime hours. Some risk for strong gusts and marginal hail appears possible, necessitating low severe probabilities.
AZ
Thunderstorms are expected once again to develop over higher terrain this afternoon/evening and spread westward across portions of central/southern AZ. Deep layer flow will be weaker compared to previous days, but modest instability and steep lapse rates amid strong heating could support sporadic strong gusts.
..Leitman/Lyons.. 07/16/2026
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
Strong to potentially severe storms are possible on Friday across parts of western Montana and northern Idaho, and also across parts of the Upper Great Lakes region.
← back to overviewSPC AC 160605
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0105 AM CDT Thu Jul 16 2026
Valid 171200Z - 181200Z
THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTHERN IDAHO AND WESTERN MONTANA AS WELL AS PORTIONS OF THE UPPER MIDWEST AND NORTHERN GREAT LAKES
### SUMMARY
Strong to potentially severe storms are possible on Friday across parts of western Montana and northern Idaho, and also across parts of the Upper Great Lakes region.
Parts of the Upper Midwest and Great Lakes
A subtle mid-level vorticity maximum evident in the 16/00 UTC guidance is expected to move southeastward across northern Minnesota and the Upper Great Lakes on Friday morning, supporting ongoing thunderstorms across the Arrowhead of Minnesota. This activity should spread southeastward through the morning with at least a marginal severe hail/wind threat.
During the day, a surface frontal zone draped from northern Illinois/Indiana should begin to lift northward, ahead of a surface cold front moving through the northern Plains. To the south of the warm front and ahead of the cold front, diurnal heating may be somewhat muted by smoke and residual cloud cover from morning convection. However, increasing low-level moisture should still support moderate destabilization by the afternoon, especially where stronger diurnal heating occurs. Moderate mid-level northwesterly flow will provide enough vertical shear to support organized storms.
As the stronger mid-level wave approaches the region during the late afternoon and evening, some potential exists for surface-based thunderstorm redevelopment – especially near the intersection of the cold front and effective warm front. Large hail and strong thunderstorm winds will be possible with these storms, and the low-level wind field would support at least some potential for a tornado with any sustained surface-based storm during the evening. With time this activity should evolve into one or more clusters of thunderstorms moving southeast overnight across the northern Great Lakes.
### Western Montana and Northern Idaho
A relatively favorable thermodynamic environment will once again be in place across parts of western Montana and northern Idaho by Friday afternoon. Relatively steep low- and mid-level lapse rates, sufficient moisture, and diurnal heating should support afternoon SBCAPE values in the 1000-1500 J/kg range, as suggested by the 20260716 00UTC HREF. Mid-/upper-level flow will be less than in previous days as the region becomes increasingly displaced from a mid-/upper-level trough/low moving northward into southwest Canada. That said, effective-layer shear on the order of 25-35 knots will be possible, especially where east/southeasterly surface winds are maintained.
Scattered thunderstorms are expected to develop during the afternoon and evening hours. The strongest thunderstorm clusters will be capable of large hail. Strong to severe thunderstorm gusts will be possible as well, especially where convective outflows can consolidate amid the steep low-/mid-level lapse rates. Most 16/00 UTC HREF members show explicit convective outflow gusts approaching 60 mph, supporting a localized severe threat.
If convective coverage appears greater than currently forecast, severe probabilities may need to be increased in subsequent outlooks.
### Ohio Valley
Scattered to numerous thunderstorms are expected to develop during the afternoon within a moist, moderately unstable, and weakly capped environment. Localized downburst winds could occur within this environment, though deep-layer flow/shear appears too weak to support an organized severe threat. Additionally, 16/00 UTC guidance suggests early initiation across the region, which would limit the development of widespread steep low-level lapse rates, which may provide some limit on a more widespread, storm-scale driven wind threat. This region will continue to be evaluated in subsequent outlooks.
..Marsh.. 07/16/2026
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
Severe thunderstorms will be possible across portions of the Ohio Valley during the late afternoon and evening hours before moving southeast toward the Mid-Atlantic overnight. Additional strong-to-severe thunderstorms will be possible during the afternoon across portions of the Mid-Atlantic.
← back to overviewSPC AC 160734
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0234 AM CDT Thu Jul 16 2026
Valid 181200Z - 191200Z
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE OHIO VALLEY INTO THE MID-ATLANTIC
### SUMMARY
Severe thunderstorms will be possible across portions of the Ohio Valley during the late afternoon and evening hours before moving southeast toward the Mid-Atlantic overnight. Additional strong-to-severe thunderstorms will be possible during the afternoon across portions of the Mid-Atlantic.
Synopsis
The CONUS-wide mid-level ridge centered over the north-central Plains for much of the past week will have retrograded west by Saturday and be located across the US and Canadian Rockies. Strong mid-level westerlies will persist on the ridge's northwest, north, and northeast periphery. Embedded within the westerlies, a series of short-wave troughs and smaller-scale vorticity/speed maxima will move across the Great Lakes and Northeast.
At the start of the forecast period, the main short-wave trough will be located across central Ontario, with its associated jet streak located across the Upper Midwest. This feature will dig southeast on Saturday, ending up in the vicinity of northern New England by Sunday morning. Ahead of this main wave, the 20260716/00 UTC guidance suite shows multiple speed/vorticity maxima moving through the west-northwesterly flow, each of which will be capable of aiding the development of scattered elevated thunderstorms.
At the surface, a weak surface low should develop Saturday morning across southern Ontario/the northern Great Lakes. This low will slowly deepen during the day as it digs southeast, reaching upstate New York by evening. Ahead of the surface low, southwesterly low-level flow will transport a very moist airmass northeast into the Lower Great lakes, with 70F surface dewpoints possible as far northeast as western New York.
To the southwest of the surface low, a surface cold front will serve as an initiating boundary for thunderstorms during the afternoon. An unstable and strongly sheared airmass will be in place by later afternoon across Ohio northeast into western New York. As thunderstorms initiate along the front, large hail will be possible before thunderstorm outflows eventually congeal into one or more linear clusters posing a threat for damaging winds. This line of storms will push south and east during the evening and overnight with a continued threat of strong, damaging thunderstorm winds.
Farther southeast across the Mid-Atlantic, most model guidance indicates the development of a surface trough to the east of the Appalachians during the late afternoon. To the east of this trough axis, temperatures will warm into the 90Fs, although there is some uncertainty how far north the hot boundary layer will extend. Given the presence of this surface trough and strong diurnal heating, several clusters of thunderstorms will be possible during the afternoon, especially if any of the previously discussed vorticity/speed maxima can interact with the low-level trough. Strong, damaging winds will be possible with any thunderstorm complex during the afternoon. Additional severe potential will also exist overnight as the remnants of the convection along the cold front approaches the region. Gusty thunderstorm winds will be the likely threat with these storms.
..Marsh.. 07/16/2026
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1930Z
You are looking at an outlook that is part of the medium range forecast (the outlook for days 4-8). The most important thing to note is that lack of a risk does not mean zero risk. Generally speaking, confidence has to be pretty high for the Storm Prediction Center to have an outlook area this far into the future.
When no specific risk areas are shown, you might see one of these phrases:
If you bookmark this page, it will continue to update with each new outlook that is issued.
| Day 4 | Sunday, July 19 | 15% |
| Day 5 | Monday, July 20 | predictability too low |
| Day 6 | Tuesday, July 21 | predictability too low |
| Day 7 | Wednesday, July 22 | predictability too low |
| Day 8 | Thursday, July 23 | predictability too low |
← back to overviewZCZC SPCSWOD48 ALL ACUS48 KWNS 160902 SPC AC 160902
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CDT Thu Jul 16 2026
Valid 191200Z - 241200Z
DISCUSSION
The mid-level pattern across the US will continue to be characterized by a West Coast trough, Intermountain West ridge, and Great Lakes/East Coast trough through the extended period. The main belt of westerlies will be found along the northern periphery of the Intermountain West ridge.
A couple of short-wave troughs will feature prominently during the forecast period. The first of these will be moving off the East Coast on Sunday (Day 4). The second will be the closed low located across the Pacific Northwest on Sunday. This low will open into a mid-level short-wave trough as it crests the Intermountain West ridge, before diving southeast across the Great Lakes early next week.
Sunday's East Coast departing mid-level wave will leave behind a surface boundary arced from Virginia west-northwest into the Upper Midwest. To the south of this boundary, a warm, moist airmass will support afternoon MUCAPE values in the 1500-2500 J/kg range, locally higher. This boundary will slowly push southward into the Carolinas during the afternoon.
Modest height falls will overspread this boundary across the Carolinas during the afternoon as a the region remains on the southern fringes of the departing wave's basal region. Additionally, a weak mid-/upper-level level low across Florida/the eastern Gulf will lift northward as it rejoins the westerlies. The combination of modest height falls, strong instability, and the presence of a surface boundary will result in scattered thunderstorm development capable of producing strong thunderstorm outflows and wind damage. A 15% area has been introduced across the Carolinas for Sunday/Day-4 to account for this potential.
The next time/area of potential concern will be across portions of the Upper Midwest/western Great Lakes on Monday/Day-5. Here, both the physics-based GEFS and EC ensemble guidance and the GFS and EC-based AI emulators are in good agreement that height falls will overspread the region ahead of the next short-wave trough. However, the GFS-based ensemble means are considerably weaker with the strength of the trough, partially owing to differences in timing of the main wave. The background environment will likely be favorable for severe thunderstorms, with MUCAPE values in the 2000-3000 J/kg range and strong vertical shear, the magnitude of which will be largely influenced by the strength of the mid-level wave. That said, west/southwesterly flow in the 925-700 millibar layer should support a strong EML given the antecedent hot and dry airmass upstream of this flow. This leads to concerns regarding convective initiation within the favorable severe background environment. These concerns are supported by the ensemble guidance with varying degrees of QPF shown within the ensemble members. Given this is still 5 days away, will hold off on introducing unconditional severe probabilities with this forecast.
..Marsh.. 07/16/2026
CLICK TO GET WUUS48 PTSD48 PRODUCT
You are looking at an outlook that is part of the medium range forecast (the outlook for days 4-8). The most important thing to note is that lack of a risk does not mean zero risk. Generally speaking, confidence has to be pretty high for the Storm Prediction Center to have an outlook area this far into the future.
When no specific risk areas are shown, you might see one of these phrases:
If you bookmark this page, it will continue to update with each new outlook that is issued.
| Day 4 | Sunday, July 19 | 15% |
| Day 5 | Monday, July 20 | predictability too low |
| Day 6 | Tuesday, July 21 | predictability too low |
| Day 7 | Wednesday, July 22 | predictability too low |
| Day 8 | Thursday, July 23 | predictability too low |
← back to overviewZCZC SPCSWOD48 ALL ACUS48 KWNS 160902 SPC AC 160902
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CDT Thu Jul 16 2026
Valid 191200Z - 241200Z
DISCUSSION
The mid-level pattern across the US will continue to be characterized by a West Coast trough, Intermountain West ridge, and Great Lakes/East Coast trough through the extended period. The main belt of westerlies will be found along the northern periphery of the Intermountain West ridge.
A couple of short-wave troughs will feature prominently during the forecast period. The first of these will be moving off the East Coast on Sunday (Day 4). The second will be the closed low located across the Pacific Northwest on Sunday. This low will open into a mid-level short-wave trough as it crests the Intermountain West ridge, before diving southeast across the Great Lakes early next week.
Sunday's East Coast departing mid-level wave will leave behind a surface boundary arced from Virginia west-northwest into the Upper Midwest. To the south of this boundary, a warm, moist airmass will support afternoon MUCAPE values in the 1500-2500 J/kg range, locally higher. This boundary will slowly push southward into the Carolinas during the afternoon.
Modest height falls will overspread this boundary across the Carolinas during the afternoon as a the region remains on the southern fringes of the departing wave's basal region. Additionally, a weak mid-/upper-level level low across Florida/the eastern Gulf will lift northward as it rejoins the westerlies. The combination of modest height falls, strong instability, and the presence of a surface boundary will result in scattered thunderstorm development capable of producing strong thunderstorm outflows and wind damage. A 15% area has been introduced across the Carolinas for Sunday/Day-4 to account for this potential.
The next time/area of potential concern will be across portions of the Upper Midwest/western Great Lakes on Monday/Day-5. Here, both the physics-based GEFS and EC ensemble guidance and the GFS and EC-based AI emulators are in good agreement that height falls will overspread the region ahead of the next short-wave trough. However, the GFS-based ensemble means are considerably weaker with the strength of the trough, partially owing to differences in timing of the main wave. The background environment will likely be favorable for severe thunderstorms, with MUCAPE values in the 2000-3000 J/kg range and strong vertical shear, the magnitude of which will be largely influenced by the strength of the mid-level wave. That said, west/southwesterly flow in the 925-700 millibar layer should support a strong EML given the antecedent hot and dry airmass upstream of this flow. This leads to concerns regarding convective initiation within the favorable severe background environment. These concerns are supported by the ensemble guidance with varying degrees of QPF shown within the ensemble members. Given this is still 5 days away, will hold off on introducing unconditional severe probabilities with this forecast.
..Marsh.. 07/16/2026
CLICK TO GET WUUS48 PTSD48 PRODUCT
You are looking at an outlook that is part of the medium range forecast (the outlook for days 4-8). The most important thing to note is that lack of a risk does not mean zero risk. Generally speaking, confidence has to be pretty high for the Storm Prediction Center to have an outlook area this far into the future.
When no specific risk areas are shown, you might see one of these phrases:
If you bookmark this page, it will continue to update with each new outlook that is issued.
| Day 4 | Sunday, July 19 | 15% |
| Day 5 | Monday, July 20 | predictability too low |
| Day 6 | Tuesday, July 21 | predictability too low |
| Day 7 | Wednesday, July 22 | predictability too low |
| Day 8 | Thursday, July 23 | predictability too low |
← back to overviewZCZC SPCSWOD48 ALL ACUS48 KWNS 160902 SPC AC 160902
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CDT Thu Jul 16 2026
Valid 191200Z - 241200Z
DISCUSSION
The mid-level pattern across the US will continue to be characterized by a West Coast trough, Intermountain West ridge, and Great Lakes/East Coast trough through the extended period. The main belt of westerlies will be found along the northern periphery of the Intermountain West ridge.
A couple of short-wave troughs will feature prominently during the forecast period. The first of these will be moving off the East Coast on Sunday (Day 4). The second will be the closed low located across the Pacific Northwest on Sunday. This low will open into a mid-level short-wave trough as it crests the Intermountain West ridge, before diving southeast across the Great Lakes early next week.
Sunday's East Coast departing mid-level wave will leave behind a surface boundary arced from Virginia west-northwest into the Upper Midwest. To the south of this boundary, a warm, moist airmass will support afternoon MUCAPE values in the 1500-2500 J/kg range, locally higher. This boundary will slowly push southward into the Carolinas during the afternoon.
Modest height falls will overspread this boundary across the Carolinas during the afternoon as a the region remains on the southern fringes of the departing wave's basal region. Additionally, a weak mid-/upper-level level low across Florida/the eastern Gulf will lift northward as it rejoins the westerlies. The combination of modest height falls, strong instability, and the presence of a surface boundary will result in scattered thunderstorm development capable of producing strong thunderstorm outflows and wind damage. A 15% area has been introduced across the Carolinas for Sunday/Day-4 to account for this potential.
The next time/area of potential concern will be across portions of the Upper Midwest/western Great Lakes on Monday/Day-5. Here, both the physics-based GEFS and EC ensemble guidance and the GFS and EC-based AI emulators are in good agreement that height falls will overspread the region ahead of the next short-wave trough. However, the GFS-based ensemble means are considerably weaker with the strength of the trough, partially owing to differences in timing of the main wave. The background environment will likely be favorable for severe thunderstorms, with MUCAPE values in the 2000-3000 J/kg range and strong vertical shear, the magnitude of which will be largely influenced by the strength of the mid-level wave. That said, west/southwesterly flow in the 925-700 millibar layer should support a strong EML given the antecedent hot and dry airmass upstream of this flow. This leads to concerns regarding convective initiation within the favorable severe background environment. These concerns are supported by the ensemble guidance with varying degrees of QPF shown within the ensemble members. Given this is still 5 days away, will hold off on introducing unconditional severe probabilities with this forecast.
..Marsh.. 07/16/2026
CLICK TO GET WUUS48 PTSD48 PRODUCT
You are looking at an outlook that is part of the medium range forecast (the outlook for days 4-8). The most important thing to note is that lack of a risk does not mean zero risk. Generally speaking, confidence has to be pretty high for the Storm Prediction Center to have an outlook area this far into the future.
When no specific risk areas are shown, you might see one of these phrases:
If you bookmark this page, it will continue to update with each new outlook that is issued.
| Day 4 | Sunday, July 19 | 15% |
| Day 5 | Monday, July 20 | predictability too low |
| Day 6 | Tuesday, July 21 | predictability too low |
| Day 7 | Wednesday, July 22 | predictability too low |
| Day 8 | Thursday, July 23 | predictability too low |
← back to overviewZCZC SPCSWOD48 ALL ACUS48 KWNS 160902 SPC AC 160902
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CDT Thu Jul 16 2026
Valid 191200Z - 241200Z
DISCUSSION
The mid-level pattern across the US will continue to be characterized by a West Coast trough, Intermountain West ridge, and Great Lakes/East Coast trough through the extended period. The main belt of westerlies will be found along the northern periphery of the Intermountain West ridge.
A couple of short-wave troughs will feature prominently during the forecast period. The first of these will be moving off the East Coast on Sunday (Day 4). The second will be the closed low located across the Pacific Northwest on Sunday. This low will open into a mid-level short-wave trough as it crests the Intermountain West ridge, before diving southeast across the Great Lakes early next week.
Sunday's East Coast departing mid-level wave will leave behind a surface boundary arced from Virginia west-northwest into the Upper Midwest. To the south of this boundary, a warm, moist airmass will support afternoon MUCAPE values in the 1500-2500 J/kg range, locally higher. This boundary will slowly push southward into the Carolinas during the afternoon.
Modest height falls will overspread this boundary across the Carolinas during the afternoon as a the region remains on the southern fringes of the departing wave's basal region. Additionally, a weak mid-/upper-level level low across Florida/the eastern Gulf will lift northward as it rejoins the westerlies. The combination of modest height falls, strong instability, and the presence of a surface boundary will result in scattered thunderstorm development capable of producing strong thunderstorm outflows and wind damage. A 15% area has been introduced across the Carolinas for Sunday/Day-4 to account for this potential.
The next time/area of potential concern will be across portions of the Upper Midwest/western Great Lakes on Monday/Day-5. Here, both the physics-based GEFS and EC ensemble guidance and the GFS and EC-based AI emulators are in good agreement that height falls will overspread the region ahead of the next short-wave trough. However, the GFS-based ensemble means are considerably weaker with the strength of the trough, partially owing to differences in timing of the main wave. The background environment will likely be favorable for severe thunderstorms, with MUCAPE values in the 2000-3000 J/kg range and strong vertical shear, the magnitude of which will be largely influenced by the strength of the mid-level wave. That said, west/southwesterly flow in the 925-700 millibar layer should support a strong EML given the antecedent hot and dry airmass upstream of this flow. This leads to concerns regarding convective initiation within the favorable severe background environment. These concerns are supported by the ensemble guidance with varying degrees of QPF shown within the ensemble members. Given this is still 5 days away, will hold off on introducing unconditional severe probabilities with this forecast.
..Marsh.. 07/16/2026
CLICK TO GET WUUS48 PTSD48 PRODUCT
You are looking at an outlook that is part of the medium range forecast (the outlook for days 4-8). The most important thing to note is that lack of a risk does not mean zero risk. Generally speaking, confidence has to be pretty high for the Storm Prediction Center to have an outlook area this far into the future.
When no specific risk areas are shown, you might see one of these phrases:
If you bookmark this page, it will continue to update with each new outlook that is issued.
| Day 4 | Sunday, July 19 | 15% |
| Day 5 | Monday, July 20 | predictability too low |
| Day 6 | Tuesday, July 21 | predictability too low |
| Day 7 | Wednesday, July 22 | predictability too low |
| Day 8 | Thursday, July 23 | predictability too low |
← back to overviewZCZC SPCSWOD48 ALL ACUS48 KWNS 160902 SPC AC 160902
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CDT Thu Jul 16 2026
Valid 191200Z - 241200Z
DISCUSSION
The mid-level pattern across the US will continue to be characterized by a West Coast trough, Intermountain West ridge, and Great Lakes/East Coast trough through the extended period. The main belt of westerlies will be found along the northern periphery of the Intermountain West ridge.
A couple of short-wave troughs will feature prominently during the forecast period. The first of these will be moving off the East Coast on Sunday (Day 4). The second will be the closed low located across the Pacific Northwest on Sunday. This low will open into a mid-level short-wave trough as it crests the Intermountain West ridge, before diving southeast across the Great Lakes early next week.
Sunday's East Coast departing mid-level wave will leave behind a surface boundary arced from Virginia west-northwest into the Upper Midwest. To the south of this boundary, a warm, moist airmass will support afternoon MUCAPE values in the 1500-2500 J/kg range, locally higher. This boundary will slowly push southward into the Carolinas during the afternoon.
Modest height falls will overspread this boundary across the Carolinas during the afternoon as a the region remains on the southern fringes of the departing wave's basal region. Additionally, a weak mid-/upper-level level low across Florida/the eastern Gulf will lift northward as it rejoins the westerlies. The combination of modest height falls, strong instability, and the presence of a surface boundary will result in scattered thunderstorm development capable of producing strong thunderstorm outflows and wind damage. A 15% area has been introduced across the Carolinas for Sunday/Day-4 to account for this potential.
The next time/area of potential concern will be across portions of the Upper Midwest/western Great Lakes on Monday/Day-5. Here, both the physics-based GEFS and EC ensemble guidance and the GFS and EC-based AI emulators are in good agreement that height falls will overspread the region ahead of the next short-wave trough. However, the GFS-based ensemble means are considerably weaker with the strength of the trough, partially owing to differences in timing of the main wave. The background environment will likely be favorable for severe thunderstorms, with MUCAPE values in the 2000-3000 J/kg range and strong vertical shear, the magnitude of which will be largely influenced by the strength of the mid-level wave. That said, west/southwesterly flow in the 925-700 millibar layer should support a strong EML given the antecedent hot and dry airmass upstream of this flow. This leads to concerns regarding convective initiation within the favorable severe background environment. These concerns are supported by the ensemble guidance with varying degrees of QPF shown within the ensemble members. Given this is still 5 days away, will hold off on introducing unconditional severe probabilities with this forecast.
..Marsh.. 07/16/2026
CLICK TO GET WUUS48 PTSD48 PRODUCT
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