SPC - No watches are valid as of Tue Jan 21 09:06:01 UTC 2025

No watches are valid as of Tue Jan 21 09:06:01 UTC 2025.

SPC MD 46

MD 0046 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF THE MIDDLE AND UPPER TEXAS COAST VICINITY

Mesoscale Discussion 0046
NWS Storm Prediction Center Norman OK
0256 AM CST Tue Jan 21 2025

Areas affected...Portions of the Middle and Upper Texas Coast
Vicinity

Concerning...Winter mixed precipitation 

Valid 210856Z - 211330Z

SUMMARY...A mix of sleet and light freezing rain/drizzle will remain
possible through daybreak. A gradual shift to snow (from north to
south) will also occur with time.

DISCUSSION...A mix of winter precipitation continues within and
north the Middle/Upper Texas Coast regions. Based on reported
precipitation and model sounding data, a mixture of sleet and
lighter freezing rain/drizzle is most likely. Given the presence of
steep lapse rates at cloud top (both noted in regional observed
soundings and model soundings), some convective elements are
possible and would be more efficient sleet producers. With time,
additional large-scale ascent will cool the atmospheric column such
that precipitation should continue to switch to all snow by daybreak
and beyond. Should freezing rain/drizzle linger, this is most likely
to be nearer the coast where the cold air may be shallow enough to
support it.

..Wendt.. 01/21/2025

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

ATTN...WFO...HGX...CRP...EWX...

LAT...LON   28049692 27649732 27679765 27819799 28169817 29139788
            29569711 30089523 30039480 29439466 28049692 

SPC MD 45

MD 0045 CONCERNING HEAVY SNOW FOR PORTIONS OF FAR WESTERN NEW YORK
        

Mesoscale Discussion 0045
NWS Storm Prediction Center Norman OK
1030 PM CST Mon Jan 20 2025

Areas affected...portions of far western New York

Concerning...Heavy snow 

Valid 210430Z - 211030Z

SUMMARY...At least 2-3 inch/hour snowfall rates should continue past
sunrise with an intense lake-effect snow band.

DISCUSSION...MRMS mosaic and KTYX radar imagery show an intense,
steady-state lake-effect snow band persisting across Jefferson and
Lewis Counties in far western NY. This snow-band is benefiting from
an optimal fetch of moisture off of Lake Ontario, where 8+ C/km 0-3
km lapse rates are in place. As such, convective snowfall within
this lake-effect band should persist past sunrise, as shown by the
latest high-resolution guidance consensus. Furthermore, given the
convective nature of the band, and degree of saturation in the
dendritic growth zone, snowfall rates at least in the 2-3 inch/hour
range are expected through the remainder of tonight.

..Squitieri.. 01/21/2025

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

ATTN...WFO...BUF...

LAT...LON   43977634 44027567 43947519 43697514 43547540 43587581
            43617612 43647630 43977634 


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SPC Jan 21, 2025 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook
      
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1046 PM CST Mon Jan 20 2025

Valid 211200Z - 221200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for thunderstorms appears negligible across the U.S. today
through tonight.

...Discussion...
Ridging to the north of the blocking mid-level high centered over
the mid-latitude eastern Pacific is rebuilding, as an initially
suppressing short wave perturbation progresses inland across British
Columbia.  The latter feature is forecast to dig through the
northern U.S. Rockies and adjacent Great Plains by 12Z Wednesday,
reinforcing large-scale troughing now encompassing much of central
and eastern North America.  As this occurs, a pair of initially
digging downstream short wave perturbations will be forced
east-northeastward, into and through strong, confluent flow between
a prominent mid-level ridge centered over the subtropical western
Atlantic and a broad cyclonic circulation centered over the far
northeastern Canadian provinces.

Although down slope flow may contribute to moderating temperatures
across the northern and central Great Plains, seasonably cold air
associated with surface ridging entrenched across much of the
southern Great Plains through Atlantic Seaboard will generally be
maintained.  It appears that the shallow leading edge of this cold
air mass will remain south and east of the Florida Peninsula and
Keys, with little in the way of surface frontal wave development
across the west central through southeastern Gulf of Mexico due to
lack of mid/upper support.

...Northwestern Gulf coast...
In the presence of steepening mid-level lapse rates associated with
differential thermal advection, it still appears that elevated
moisture return will contribute to weak destabilization (rooted in
the 800-700 mb layer) as far northwest as upper Texas/Louisiana
coastal areas by 12-15Z this morning.  This probably will provide
support for a period of increasing convective development, with
thermodynamic profiles possibly become conducive to at least some
lightning production before diminishing by early afternoon.  There
remains substantive spread concerning this potential, however, and
thunderstorm probabilities will be maintained at less than 10
percent, based on objective calibrated guidance from both the NCEP
SREF and HREF.

..Kerr.. 01/21/2025


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SPC Jan 21, 2025 0700 UTC Day 2 Convective Outlook

SPC 0700Z Day 2 Outlook
      
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1048 PM CST Mon Jan 20 2025

Valid 221200Z - 231200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected on Wednesday.

...Synopsis...
A large upper trough will remain over all but the westernmost CONUS
on Wednesday, with a leading trough exiting the East Coast early in
the day. At that time, high pressure will firmly be in place over
the East, with strong north winds over the Gulf of Mexico and
western Atlantic. A weak surface low may develop along the front
over the Bahamas, but low-level moisture and instability is forecast
to remain off the FL Peninsula.

Behind this system, another upper trough will develop out of the
Rockies and into the central states, with another strong area of
high pressure centered over the Intermountain West into Thursday
morning. The cool and/or stable air mass over land will thus
maintain little if any chance of thunderstorms through the period.

..Jewell.. 01/21/2025


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SPC Jan 21, 2025 0830 UTC Day 3 Severe Thunderstorm Outlook

SPC 0830Z Day 3 Outlook
      
Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0117 AM CST Tue Jan 21 2025

Valid 231200Z - 241200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast on Thursday.

...Synopsis...
A cool and stable pattern will persist on Thursday across the CONUS
with an expansive upper trough  over much of the central states and
into the Great Lakes. This trough may amplify as it becomes more
progressive and moves into the MS Valley by 12Z Friday. A strongly
cyclonic speed max will exist along the northern Gulf Coast, with
cooling aloft to the north.

At the surface, another installment of high pressure will push into
the Gulf of Mexico, with further drying. Any appreciable low-level
moisture will remain east of the FL Peninsula, and as such,
thunderstorms are not forecast.

..Jewell.. 01/21/2025


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SPC Jan 21, 2025 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook
      
Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0302 AM CST Tue Jan 21 2025

Valid 241200Z - 291200Z

...DISCUSSION...
An amplified and progressive upper trough will move quickly from the
MS Valley to the East Coast on Friday/D4, with zonal flow developing
behind this system. High pressure will follow, maintaining dry
offshore winds across the Southeast.

Models remain in relatively good agreement with the large-scale
pattern through the weekend, depicting a positive-tilt upper trough
over the southwestern states. A broad fetch of west/southwest flow
aloft is forecast to extend across the southern Plains and into much
of the East, with the deep upper low over eastern Canada. Sufficient
instability is forecast to develop across parts of southern and
eastern TX into the lower MS Valley Saturday/D5 Night into
Sunday/D6. Given the antecedent cool air at the surface, substantial
clouds and precipitation appear likely, reducing overall
destabilization and severe potential. 

Models diverge around Monday/D7, with uncertainly regarding whether
another wave will develop into the northern Plains and Great Lakes
as disturbances rotate around the large-scale low. To the west, the
trough/low over the Southwest may eventually eject east, but timing
for this is uncertain as well with low predictability at this time
frame. In any case, severe potential is forecast to be low through
the period.


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SPC Day 1 Fire Weather Outlook

SPC Day 1 Fire Weather Outlook
          
Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0156 AM CST Tue Jan 21 2025

Valid 211200Z - 221200Z

...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE VENTURA
VALLEY TO THE SAN BERNARDINO MOUNTAINS IN SOUTHERN CALIFORNIA...
...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SAN
JACINTO TO LAGUNA MOUNTAIN RANGES...
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...

...Synopsis...
A mid-level trough across the southwest U.S. will rapidly track
eastward toward the Southeast while surface high pressure persists
over the Great Basin through the period. Strong offshore flow will
persist from the Ventura Valley to the Laguna Mountains, with
widespread 20-30 mph sustained winds and 10 percent RH expected
during the day into early Wednesday morning, warranting the
maintenance of Critical highlights across much of the far southern
California shoreline. Furthermore, the latest high-resolution
guidance consensus shows sustained winds exceeding 40 mph,
coinciding with single-digit RH, from the Ventura Valley to the San
Bernardino Mountains, as well as the San Jacinto to Laguna Mountain
ranges, where Extremely Critical highlights were maintained. The
best chance for Extremely Critical conditions will be during the
morning into early afternoon hours.

..Squitieri.. 01/21/2025

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


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SPC Day 2 Fire Weather Outlook

SPC Day 2 Fire Weather Outlook
          
Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0157 AM CST Tue Jan 21 2025

Valid 221200Z - 231200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...

...Synopsis...
A surface pressure gradient will persist across southern California,
with some strengthening of the gradient likely by late Wednesday
afternoon as another in a series of mid-level troughs overspread the
Great Basin tomorrow (Wednesday). Another day of offshore flow
capable of supporting rapid wildfire spread is expected. By
afternoon peak heating, widespread sustained 20-30 mph wind speeds
are likely, along with RH dropping to at least the 10-15 percent
range. Locally higher wind speeds/gusts are also likely in
terrain-favoring areas. Anywhere from the Ventura Valley region to
the Laguna Mountains may experience the aforementioned
meteorological surface conditions, necessitating the introduction of
Critical fire weather highlights this outlook.

..Squitieri.. 01/21/2025

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


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