SPC Forecast Products

Current Mesoscale Discussions


SPC - No watches are valid as of Sat Jul 13 10:54:02 UTC 2024

No watches are valid as of Sat Jul 13 10:54:02 UTC 2024.


SPC - No MDs are in effect as of Sat Jul 13 10:54:02 UTC 2024

No Mesoscale Discussions are in effect as of Sat Jul 13 10:54:02 UTC 2024.


SPC Jul 13, 2024 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook
      
Day 3 Outlook Image
Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0229 AM CDT Sat Jul 13 2024

Valid 151200Z - 161200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE UPPER
MIDWEST INTO PORTIONS OF THE MID MS VALLEY AND UPPER GREAT LAKES...

...SUMMARY...
Strong to severe thunderstorms are possible from the Upper Midwest
into the Mid Mississippi Valley and Upper Great Lakes region on
Monday.

...Synopsis and Discussion...
A belt of modestly cyclonic flow will likely be in place across the
northern CONUS early Monday morning, with this belt situated between
upper ridging across the southern CONUS and upper troughing across
north-central Canada. A shortwave trough is expected to progress
through this cyclonic flow, moving from southern Manitoba/ND
eastward across far northwest Ontario/northern MN before lifting
into more of northwest Ontario. Another convectively augmented
shortwave trough may move from SD and NE through the Mid MS Valley,
briefly phasing with the northern shortwave trough. 

Thunderstorms will likely be ongoing Monday morning over western MN,
along and ahead of a modest cold front. These storms should be north
of the warm front, which is expected to extend from a surface low
near the SD/MN/IA border intersection vicinity east-southeastward to
far northern IL. Two scenarios appear plausible with these storms:
1) continued progression southeastward throughout the day ahead of
the cold front with a transition to a more surface-based character
possible amid interaction with the warm front, or 2) dissipation
with new development or significant reintensification occurring near
the warm front during the afternoon. Both scenarios suggest the
development of a forward-propagating MCS is possible, with the most
likely corridor for this MCS from eastern IA and southern WI across
northern IL, potentially reaching southwest Lower MI and northern
IN. Damaging gusts would be the primary threat within this MCS.

Afternoon/early evening thunderstorms are possible farther east from
the Upper OH Valley into the Northeast as a modest shortwave trough
interacts with the warm and moist airmass over the region. Shear
will likely be weak, mitigating the organized storm potential and
likely keeping the severe threat isolated.

..Mosier.. 07/13/2024

Read more

SPC Jul 13, 2024 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook
      
Day 4-8 Outlook Image
Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0318 AM CDT Sat Jul 13 2024

Valid 161200Z - 211200Z

...DISCUSSION...
Western CONUS upper ridging is expected to build throughout much of
the week, with this expansive ridging likely extending into much of
western Canada by the end of the week. Modest upper troughing is
anticipated over much of the central and eastern CONUS. A series of
shortwave troughs will likely move through this upper troughing,
helping to push a cold front gradually southward/eastward from
D4/Tuesday through D7/Friday. 

Thunderstorms are anticipated along the front, with strong buoyancy
and moderate shear potentially supporting strong to severe storms
from the OH Valley into the Northeast on D4/Tuesday. Some severe
potential may linger across the Northeast on D5/Wednesday before the
front clears the region. After D5/Wednesday, progression of the
front will displace the better low-level moisture south of the
stronger flow aloft, limiting the severe-storm potential across much
of the central and eastern CONUS from D6/Thursday through
D8/Saturday. The only exception is across the High Plains, where
modest low-level moisture beneath vertically veering wind profiles
could support a few strong to severe storms.

Read more

SPC Day 2 Fire Weather Outlook

SPC Day 2 Fire Weather Outlook
          
Day 2 Fire Weather Outlook Image
Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0121 AM CDT Sat Jul 13 2024

Valid 141200Z - 151200Z

...Synopsis...
Dry thunderstorms will continue to be the primary fire weather
concern for Sunday across much of the western CONUS, though areas of
dry/windy conditions are also probable across parts of southeast OR
into southern ID. 

...Dry Thunderstorms - Great Basin/Pacific Northwest...
Lift ahead of a weak mid-level perturbation is expected to
overspread the northern Great Basin and Pacific Northwest through
peak heating Sunday afternoon. A plume of 0.5-1.0 inch PWAT values
currently advecting north into the Great Basin is forecast to be in
place ahead of this ascent, and will support the potential for
isolated to scattered thunderstorms. Dry low-level conditions and
storm motions near 20 knots should support the potential for dry
lightning. While convection is anticipated across a broad swath of
the West, dry thunderstorm coverage may be slightly higher across
portions of the northern Great Basin/Pacific Northwest on Sunday as
compared to today/Saturday while the mid-level perturbation moves
north. Latest ensemble guidance shows very low (30% or lower)
probability for wetting rainfall across the delineated
dry-thunderstorm risk area where ERC values are near/above the 90th
percentile based on recent fuel guidance. 

...Southeast Oregon into southern Idaho...
Subsequent days of mid-level diabatic heat release associated with
isolated to scattered thunderstorms under the upper ridge is
forecast to result in a gradual de-amplification and eastward shift
of the ridge into the Four Corners by Sunday afternoon.
Concurrently, most model solutions depict an upper shortwave trough
moving into the northern Rockies out of Canada, which will support
lee troughing along the northern High Plains. The combination of the
eastward shift of the upper ridge and deepening surface trough
should result in a broad region of around 15 mph winds across the
Great Basin, northern Rockies, and High Plains. Thunderstorm
development over the next 48 hours is not expected to appreciably
modify the very warm/dry air mass currently in place, so
single-digit to low-teen RH values, combined with modest gradient
winds, should result in a broad swath of localized/transient
elevated conditions. Elevated highlights are maintained/expanded
from roughly the Harney Basin in southeast OR into the Snake River
Plain of southern ID, where regional topographic effects should
result in corridor of slightly stronger (15-20 mph) winds for a few
hours Sunday afternoon (though this may be conditional on minimal
cloud cover from developing convection).

..Moore.. 07/13/2024

...Please see www.spc.noaa.gov/fire for graphic product...

Read more