SPC Forecast Products

Current Mesoscale Discussions


SPC - No watches are valid as of Thu Aug 5 11:13:01 UTC 2021

No watches are valid as of Thu Aug 5 11:13:01 UTC 2021.


SPC - No MDs are in effect as of Thu Aug 5 11:13:01 UTC 2021

No Mesoscale Discussions are in effect as of Thu Aug 5 11:13:01 UTC 2021.


SPC Aug 5, 2021 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
0201 AM CDT Thu Aug 05 2021

Valid 071200Z - 081200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN SOUTH
DAKOTA AND NEBRASKA ACROSS IOWA...SOUTHERN MINNESOTA...AND WESTERN
WISCONSIN...

...SUMMARY...
Scattered storms, some severe, are expected Saturday from the
northern Plains toward the upper MS Valley.

...Northern Plains/Upper MS Valley...
A shortwave trough will move east across the northern Plains on
Saturday, providing 30-40 kt midlevel flow and cooling aloft. With
only a weak cool surge behind the upper wave, the surface trough
will move little during the day, remaining over the Dakotas and
central NE.

Early day storms are possible near the nose of a southwesterly
low-level jet, from MN into WI, but severe weather is unlikely due
to weak shear. Southwest of this area, southerly winds will aid
moisture transport throughout the day. Upper 60s F dewpoints will
develop ahead of the surface trough, and heating will boost MLCAPE
above 2000 J/kg over a large area.

While deep-layer shear may only average 30-35 kt, 850 mb winds will
increase to 40 kt by 00Z, enlarging low-level parts of the hodograph
with effective SRH to 200 m2/s2. Storms are likely to form over
eastern SD and NE after 21Z, developing slowly eastward across MN,
IA and WI during the evening. Mixed-mode severe is possible,
including brief supercells, but several clusters of storms are
possible resulting in interference. Sporadic severe reports of wind,
hail, and perhaps a brief/weak tornado will all be possible.

...Central KS into the TX Panhandle...
A stalling front will likely provide sufficient lift for at least
isolated afternoon storms near peak heating in a narrow zone from
central KS into the northern TX Panhandle. The air mass farther east
is likely to remain capped, limiting storm coverage after 03Z.
MUCAPE of 1000-1500 J/kg along with modest westerlies aloft may
support a few persistent cells capable of marginal hail or strong
wind gusts.

..Jewell.. 08/05/2021

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SPC Aug 5, 2021 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
0325 AM CDT Thu Aug 05 2021

Valid 081200Z - 131200Z

...DISCUSSION...
On Sun/D4, models indicate a leading shortwave trough will move
slowly eastward across the upper MS valley, where upper 60s to lower
70s F dewpoints will exist. Scattered thunderstorms are likely to be
ongoing with this wave across IA, MN, and WI, which will limit
destabilization and decreases predictability for further severe
potential during the day.

For the Mon/D5 to Thu/D8 period, although there is now better
run-to-run consistency with the ECMWF, major differences remain
among the models regarding a consolidating shortwave trough evolving
out of MT. The ECMWF is much slower and not as deep as GFS members,
which produce significant cyclonic flow aloft across the Great
Lakes. Given vast model differences, predictability is too low to
outline severe threat areas. However, low-level moisture and
instability will be present ahead of whatever upper trough may
eventually affect the northern Plains, upper MS Valley and Great
Lakes.

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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
0204 AM CDT Thu Aug 05 2021

Valid 061200Z - 071200Z

...NO CRITICAL AREAS...

...Synopsis...
The upper-level wave currently off the northern California coast is
forecast to progress over northern/central Rockies through the day
Friday. The resulting lee troughing will drive an increase in
pressure-gradient winds across the central Plains and parts of the
eastern Great Basin that may foster elevated to critical wind/RH
combinations. Additionally, isolated dry thunderstorms will be
possible along the central Rockies. 

...Great Basin and central High Plains...
Confidence is reasonably high that a deepening lee trough over the
northern to central High Plains will strengthening winds across the
central High Plains and into the eastern Great Basin. Sustained
winds between 15-25 mph appear likely for both regions, and an
antecedent dry airmass in place over the Great Basin and meager
moisture return over the Plains will support RH reductions into the
teens and 20s. While elevated (to locally critical) wind/RH
combinations are likely, ERC values below seasonal normal will limit
the fire weather risk. Fuel status will be monitored over the next
24 hours to determine if highlights are needed. 

...Central Rockies - Dry Thunderstorms...  
Dry thunderstorms are probable Friday afternoon from southern WY
into central CO, and may occur as far south as northern NM. A
combination of cooling temperatures aloft and meager mid-level
moisture (PWAT values near 0.6 inches) atop a dry, well-mixed
boundary layer suggests mostly dry thunderstorms are likely. Lift
ahead of the main trough axis will likely support at least isolated
thunderstorm coverage by the mid to late afternoon hours. Despite
the favorable thermodynamic conditions, fuels across the region are
generally unreceptive and will temper the dry lightning threat to
some degree.

..Moore.. 08/05/2021

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

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