• 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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