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MESO: Freezing rain
From
Weather Alert@21:1/175 to
All on Sat Feb 13 02:04:00 2021
ACUS11 KWNS 130155
SWOMCD
SPC MCD 130155
ORZ000-130700-
Mesoscale Discussion 0071
NWS Storm Prediction Center Norman OK
0755 PM CST Fri Feb 12 2021
Areas affected...Portions of Willamette Valley
Concerning...Freezing rain
Valid 130155Z - 130700Z
SUMMARY...Freezing rain rates are expected to increase this evening,
especially within the 7-11 PM time window. Areas within the
Willamette Valley west of Portland are most likely to see higher ice accumulations. Precipitation in Portland will remain snow with a
transition to freezing rain and sleet towards early Saturday
morning.
DISCUSSION...Surface high pressure into the Columbia Basin has
helped to maintain easterly/northeasterly surface winds into the
Willamette Valley. With the approach of a strong Pacific trough this
evening, coverage and intensity of precipitation should increase.
Current KRTX reflectivity trends indicate that this process is
underway. Light freezing rain has been observed for several hours
from just west of Portland and southward to near Salem. These areas
are the most likely to see larger ice accumulations. While Portland
is currently observing snowfall, it will be near the transition zone
to freezing rain/sleet. Forecast soundings do indicate that freezing
rain and sleet are possible towards 2-4 AM PST. The exact evolution
of the transition zone will be dependent on the surface low
developing west of the Washington coast. Current observations
indicate a preference for a more northerly track which would
indicate higher probability of transition away from snow later
tonight. While heavy snow is also possible with this trough, the
heaviest snowfall rates are expected to remain within the Cascades
northward into the western Puget Sound and adjacent Olympic
Peninsula.
..Wendt.. 02/13/2021
ATTN...WFO...PQR...
LAT...LON 44962350 45882353 45962340 45972315 45762290 45452279
44872297 44622317 44582338 44732347 44962350
$$
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From
Weather Alert@21:1/175 to
All on Sat Feb 13 15:13:00 2021
ACUS11 KWNS 131503
SWOMCD
SPC MCD 131502
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-132100-
Mesoscale Discussion 0076
NWS Storm Prediction Center Norman OK
0902 AM CST Sat Feb 13 2021
Areas affected...portions of the Mid-Atlantic
Concerning...Freezing rain
Valid 131502Z - 132100Z
SUMMARY...Areas of freezing rain and occasional sleet will impact
much of the Mid-Atlantic through early afternoon.
DISCUSSION...A broad area of ascent/isentropic lift atop a shallow
cold airmass continues to contribute to widespread freezing rain at
this time. The freezing rain is reportedly mixing with sleet at
times across the DC/Baltimore MD areas, though a transition to more
freezing rain should occur in that area over time as models indicate
warm advection in the H7-H85 layer. Precipitation rates may
approach 0.05 inch/hour at times beneath heavier precipitation
bands. The general regime should persist through early afternoon,
with a general northeastward expansion of the precipitation shield
toward Delaware/southern New Jersey and the Philadelphia area over
the next couple hours or so. Several models/CAMs shift
precipitation out of much of Virginia and western Maryland around
21Z.
..Cook.. 02/13/2021
ATTN...WFO...PHI...AKQ...CTP...LWX...RNK...
LAT...LON 39087815 39347734 39967564 40067489 39757443 39527439
39407450 38747502 37587660 36827786 36617874 36767934
36957986 37308004 37827988 39087815
$$
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From
Weather Alert@21:1/175 to
All on Mon Feb 15 20:58:00 2021
ACUS11 KWNS 151945
SWOMCD
SPC MCD 151944
PAZ000-MDZ000-WVZ000-OHZ000-KYZ000-160145-
Mesoscale Discussion 0091
NWS Storm Prediction Center Norman OK
0144 PM CST Mon Feb 15 2021
Areas affected...northeastern Kentucky...southern/eastern Ohio...western/central Pennsylvania...northern West Virginia
Concerning...Freezing rain
Valid 151944Z - 160145Z
SUMMARY...Precipitation will expand from southwest to northeast
across the discussion area. 0.05 to 0.10 inch per 3-hour
accumulations of freezing rain are expected.
DISCUSSION...Radar mosaic imagery continues to indicate an expanding precipitation shield across the majority of the state of Kentucky
atop a shallow, sub-freezing airmass. The precipitation continues
to outpace northeastward-movement of most model guidance outside of
certain CAMS (Nam3, HRRR). These CAMS indicate continued
northeastward progression of icing (freezing rain and some sleet)
into Ohio/northern West Virginia over the next hour or so and
southwestern Pennsylvania after around 22Z or so. Upstream
observations have indicated localized precipitation rates ranging as
high as 0.05 to 0.10 inch per hour in heavier bands/convective
elements, and the expectation is that this will continue with
northeastward extent across the discussion area over the next 6
hours. At least 3-6 hours of icing is expected areawide.
Additionally, a few areas of sleet (or even snow) are expected to
mix in with freezing rain - especially across the northern extent of
the discussion area where deeper cold air is present.
..Cook.. 02/15/2021
ATTN...WFO...CTP...LWX...PBZ...RLX...CLE...JKL...ILN...
LAT...LON 39538328 40238243 40938123 41277968 41337835 41037733
40337715 39857766 39557870 39427989 38408161 37918224
38078339 38448382 38948383 39538328
$$
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From
Weather Alert@21:1/175 to
All on Wed Feb 17 21:05:00 2021
ACUS11 KWNS 171653
SWOMCD
SPC MCD 171653
ALZ000-MSZ000-ARZ000-LAZ000-TXZ000-172300-
Mesoscale Discussion 0109
NWS Storm Prediction Center Norman OK
1053 AM CST Wed Feb 17 2021
Areas affected...northern/central Louisiana into much of Mississippi
Concerning...Freezing rain
Valid 171653Z - 172300Z
SUMMARY...Areas of moderate to heavy freezing rain will persist
across Louisiana today while expanding eastward into Mississippi
this afternoon.
DISCUSSION...A large shield of precipitation continues across much
of Louisiana and eastern Texas currently. The precipitation is
enhanced by strong low-level flow (with 50-55kts of southerly flow
indicated in the 1-2km layer at HGX) and isentropic lift atop a
shallow, cold airmass residing across the region. Meanwhile, light northeasterly surface trajectories will help in maintaining a
shallow, sub-freezing airmass across much of the discussion area
over the next several hours. Upstream observations have indicated
up to .25 inch per hour of freezing rain rates in heavier bands.
0.05 to 0.20 inch per hour freezing rain rates will be possible in
many areas through 21Z, though precipitation may taper across
western Louisiana around that time as forcing for ascent (attendant
to the stronger low-level flow) shifts east of the area. On the
southern end of the discussion area, freezing rain may change over
to rain later this afternoon as warm advection erodes the
near-surface cool layer.
..Cook.. 02/17/2021
ATTN...WFO...BMX...MOB...MEG...JAN...LIX...LZK...LCH...SHV...
LAT...LON 30859307 31119353 31779369 32659344 33039299 33179242
33519145 33849061 34088997 34578897 34618857 34428833
34148817 33878817 32728832 32238841 31638895 31399040
31139165 30859307
$$
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