RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Tue Jan 21 00:54:01 UTC 2025.
MD 0041 CONCERNING HEAVY SNOW FOR PORTIONS OF FAR WESTERN NEW YORK
Mesoscale Discussion 0041
NWS Storm Prediction Center Norman OK
0439 PM CST Mon Jan 20 2025
Areas affected...portions of far western New York
Concerning...Heavy snow
Valid 202239Z - 210245Z
SUMMARY...Instances of heavy lake-effect snow should continue
through the evening, with 2 inch/hour snowfall rates possible,
especially over Erie County, New York.
DISCUSSION...Deep-layer flow (especially closer to the surface) has
become more aligned with the long axis of Lake Erie over the past
couple of hours given the passing of a weak surface trough. The long
fetch of appreciable low-level moisture off of the lake waters will
support lake effect snow into the evening hours. 6-7 C/km low-level
lapse rates (evident via 22Z mesoanalysis) will support continued
heavier snowfall (as was recently observed at the DKK ASOS), with
snowfall rates potentially approaching 2 inches/hour at times.
..Squitieri.. 01/20/2025
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BUF...
LAT...LON 42667911 42767897 42817890 42907887 42927861 42777847
42617851 42527878 42517889 42577899 42667911
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SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0647 PM CST Mon Jan 20 2025
Valid 210100Z - 211200Z
...NO THUNDERSTORM AREAS FORECAST...
...SUMMARY...
The risk for thunderstorms appears negligible across the U.S.
tonight.
...01Z Update...
Cold surface ridging has become entrenched across much of the
interior U.S. through much of the Gulf Basin and offshore western
Atlantic coastal waters. This will become reinforced overnight
across the southern Great Plains through middle and southern
Atlantic Seaboard, downstream of a pair of digging short wave
troughs, where confluent mid-level flow will be maintained to the
northwest of a prominent ridge centered over the subtropical western
Atlantic.
In advance of the southwestern of the two perturbations digging
within positively tilted larger scale troughing, currently across
the Southwest and adjacent international border vicinity, warm
thermal and moisture advection is ongoing above the cold
surface-based air across the western Gulf of Mexico into
northwestern Gulf coast vicinity. This is supporting increasing
precipitation offshore of the lower Texas coast, which is forecast
to expand northeastward and eastward across much of the northwestern
Gulf/Gulf Coast region by late tonight.
Model forecast soundings continue to suggest that elevated
destabilization, rooted within the 800-700 mb layer, is possible
ahead of developing weak surface troughing as far northwest as the
upper Texas coast by 12Z Tuesday. The NAM soundings, in particular,
continue to indicate profiles which could become supportive of
convection capable of producing lightning. However, based on the
objective calibrated guidance of both the NCEP SREF and HREF,
probabilities for this still appear less than the minimum 10 percent
threshold for a categorical thunder area.
..Kerr.. 01/21/2025
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SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0400 PM CST Mon Jan 20 2025
Valid 221200Z - 281200Z
...Southern California - Days 3-4/Wednesday-Thursday...
Within a belt of broad northwesterly flow aloft across the West, an
embedded shortwave trough will track southeastward across the Great
Basin into the southern Rockies/High Plains. At the same time, an
upstream midlevel ridge will build over the eastern Pacific and West
Coast. This will favor strengthening surface high pressure over the
Intermountain West, forcing a strong offshore pressure gradient
across southern CA (LAX-DAG pressure gradient around -5 to -7 mb).
Given a very dry air mass in place, critical fire-weather conditions
are expected over the wind-prone Santa Ana Corridor surrounding the
LA Basin, as well as along the mountains/valleys in San Diego
County. Current indications are that this event will peak Day
3/Wednesday night into Day 4/Thursday morning.
Thereafter, onshore flow should develop across southern CA, reducing
the fire-weather threat through the weekend.
...Southwest into the southern Rockies and High Plains...
Dry breezy conditions are expected across the region from Day
5/Friday into the weekend ahead of a large-scale trough. However,
any fire-weather concerns should remain fairly localized owing to
marginal fuels -- precluding Critical probabilities at this time.
..Weinman.. 01/20/2025
...Please see www.spc.noaa.gov/fire for graphic product...
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