SPC Forecast Products

Current Mesoscale Discussions


SPC - No watches are valid as of Mon Jan 25 22:51:03 UTC 2021

No watches are valid as of Mon Jan 25 22:51:03 UTC 2021.


SPC MD 33

MD 0033 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR NORTHERN/CENTRAL MISSISSIPPI...WESTERN/MIDDLE TENNESSEE...NORTHWEST ALABAMA
MD 0033 Image


Mesoscale Discussion 0033
NWS Storm Prediction Center Norman OK
0449 PM CST Mon Jan 25 2021

Areas affected...Northern/Central Mississippi...Western/Middle
Tennessee...Northwest Alabama

Concerning...Severe potential...Watch possible 

Valid 252249Z - 260015Z

Probability of Watch Issuance...60 percent

SUMMARY...Scattered strong thunderstorms are expected across the
Mid-South into Middle TN this evening. Some risk for tornadoes may
necessitate a watch in the next couple of hours.

DISCUSSION...Strong mid-level short-wave trough is ejecting across
the central Plains this evening. The more appreciable height falls
will spread across the Mid-MS into the OH Valley region. Along the
southern fringe of this stronger large-scale forcing, robust
convection has recently developed across portions of western TN
where surface dew points have risen into the mid 60s with surface
temperatures in the lower 70s. This activity should spread
east-northeast along a corridor that is destabilizing just south of
a well-defined warm front. Ample shear/buoyancy exist for supercells
(possibly tornadic supercell ongoing over Fayette County TN) and
there is increasing concern/confidence that other organized
longer-lived storms may develop.

Farther south along the Pacific front, showers are gradually
deepening from northwest MS into northeast LA. Some lightning is
noted with the stronger updrafts but activity has struggled to
organize. It's not entirely clear how many organized supercells
can/will develop along this zone, but shear/buoyancy do favor some
tornado threat. Tornado watch may be warranted for this activity in
the next couple of hours.

..Darrow/Thompson.. 01/25/2021

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

ATTN...WFO...OHX...BMX...HUN...MEG...JAN...

LAT...LON   33159055 35478893 35888710 35008651 33568819 32718919
            33159055 

Read more

MD 0000 CONCERNING


SPC Jan 25, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0156 PM CST Mon Jan 25 2021

Valid 252000Z - 261200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING
ACROSS PARTS OF NORTHEASTERN MISSISSIPPI AND NORTHWESTERN ALABAMA
INTO MIDDLE TENNESSEE...

...SUMMARY...
A few severe thunderstorms are possible this evening within a
corridor across northeastern Mississippi and northwestern Alabama
into middle Tennessee.  This includes a risk for potentially
damaging wind gusts and perhaps a couple of tornadoes.

...20Z Outlook Update...
Adjustments to the categorical and probabilistic outlook lines were
made to account for the progression of synoptic and sub-synoptic
features, and latest trends concerning ongoing destabilization.

...Mid South vicinity...
Low-level moisture return is ongoing on southerly return flow across
the lower Mississippi into Tennessee Valleys.  This appears to be
contributing to modest boundary-layer destabilization (including
CAPE  up to 500-1000 J/kg), which is expected to continue developing
northeastward as an initial short wave impulse, which has emerged
from the Southwest, progresses east-northeast of the central Great
Plains late this afternoon and evening.  As the associated frontal
wave migrates into the lower Ohio Valley, there appears a window of
opportunity for vigorous convective development focused along/just
ahead of the trailing surface trough across Tennessee into
Mississippi.  This may coincide with a 40-50 kt southerly 850 mb jet
axis, along which enlarged low-level hodographs may become support
of supercells structures accompanied by the risk for damaging wind
gusts and/or a couple of tornadoes.  With the influence of the
mid/upper forcing on the warm sector expected to be
glancing/short-lived, it appears this risk will be maximized this
evening, but at least some severe weather potential may linger as
remnant convection spreads eastward/southeastward overnight.

...Arizona...
A corridor of modest boundary-layer destabilization is ongoing
across the international border into southern Arizona, ahead of the
vigorous short wave impulse now turning inland of the southern
California coast.  Coincident with strengthen of west-southwesterly
flow to 30-40+ kt in the 850-700 mb layer, the environment may
become conducive for isolated thunderstorm development with the
potential to produce strong surface gusts approaching or briefly
exceeding severe limits.

..Kerr.. 01/25/2021

.PREV DISCUSSION... /ISSUED 1025 AM CST Mon Jan 25 2021/

...TN Valley today...
A progressive shortwave trough continues to move across the central
Plains today, with an associated 100kt+ mid level jet extending from
north TX into MO.  The primary surface low for this system is over
northwest AR, with a warm front extending eastward along the KY/TN
border.  Strong low-level wind fields are present across the warm
sector, with sufficient CAPE to pose a marginal risk of a few
fast-moving storms capable of gusty winds.  However, model guidance
continues to suggest that slight veering in the low-level winds will
weaken convergence/forcing and limit coverage of deep convection.

...MS/AL/TN this evening and tonight...
After dark, a few thunderstorms are expected to form over parts of
MS/Al and middle TN along/ahead of the advancing cold front. 
Low-level and deep-layer vertical shear profiles in this area will
be favorable for storm organization/rotation, and will maintain the
marginal probabilities for isolated tornadoes or damaging wind
gusts.  The primary forecast concern in this region will be storm
coverage, and poor thermodynamics in the lowest 3-4 km suggest that
updrafts may struggle to intensify.  This area will continue to be
evaluated in later outlooks.

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
1256 PM CST Mon Jan 25 2021

Valid 261200Z - 271200Z

...NO CRITICAL AREAS...

No changes to the ongoing forecast.

..Wendt.. 01/25/2021

.PREV DISCUSSION... /ISSUED 0136 AM CST Mon Jan 25 2021/

...Synopsis...
Large scale troughing is forecast to continue across the West as
high pressure develops across the northern and central US. With an
abundance of cool air moving in from the north and widespread
precipitation expected, overall fire weather potential is low across
much of the CONUS.

...Texas Trans Pecos...
Dry downslope winds of 15-20 mph and humidity values of 15-25% will
likely support at least locally elevated to near critical fire
weather conditions across a small portion of the Rio Grande Valley
toward the Texas Big Bend. While fuels remain receptive to fire
spread given the lack of recent precipitation, fuel coverage remains
sparse across this area. In addition, the temporal window for
favorable fire weather conditions is expected to be rather narrow,
with the fast-moving cold front bringing cooler temperatures and
higher humidity into the area by late afternoon. This suggests any
fire weather threats that do develop will likely remain local in
nature, negating the need for an elevated delineation at this time.

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

Read more