ACUS11 KWNS 201440
SWOMCD
SPC MCD 201439=20
PAZ000-MDZ000-NYZ000-WVZ000-VAZ000-201615-

Mesoscale Discussion 0838
NWS Storm Prediction Center Norman OK
0939 AM CDT Fri May 20 2022

Areas affected...much of central Pennsylvania into far northern
Maryland

Concerning...Severe potential...Watch likely=20

Valid 201439Z - 201615Z

Probability of Watch Issuance...80 percent

SUMMARY...The severe threat is increasing across portions of central
PA into MD. Damaging gusts and perhaps a few tornadoes may accompany
the strongest, longer lived storms. A WW issuance will be needed
within the next couple of hours.

DISCUSSION...A remnant mid-level MCV (evident via water vapor
imagery and 700-500 mb objective analysis fields) is currently
located just west of the OH/PA border and continues to track
eastward towards central PA, and is expected to support more robust
convective initiation in the next few hours. Immediately ahead of
the MCV center lies a highly sheared low-level environment, with
recent PBZ VAD data showing relatively long, curved low-level
hodographs and over 300 m2/s2 of associated 0-1km SRH. At the
moment, buoyancy remains scant across portions of western into
central PA. However, modest breaks in the clouds are contributing to
modest surface heating, with mid 60s F surface temperatures already
noted across central PA, with low 70s F along the PA/MD border. With
surface dewpoints around 60F across several locales, RAP forecast
soundings suggest temperatures need to warm into the lower 70s for
appreciable buoyancy to develop given the presence of relatively
poor (5.5-6.5 C/km) low and mid-level lapse rates.

While buoyancy is expected to initially be marginal (i.e. at or
below 1000 J/kg MLCAPE), localized deep-layer ascent and strong
low-level shear associated with the approaching MCV should support
at least a few strong to severe storms developing early this
afternoon. Damaging gusts and perhaps a few tornadoes will be the
primary concerns, though a brief instance or two of marginally
severe hail cannot be completely ruled out with the longer-lived,
persistent rotating updrafts. A WW issuance will be needed within
the next couple of hours to address the severe threat.

..Squitieri/Hart.. 05/20/2022

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!4A7jNtZRb04qjMa86S81TtfpClxqknFoO-jWcgrS4GGODzuK2uwDrMxNDssmczPNSj9e152Ea= bgUguz8o50x-xu3u-Q$ for graphic product...

ATTN...WFO...PHI...BGM...CTP...LWX...PBZ...

LAT...LON 39507942 40487929 41477881 41867804 42007731 41887681
41487648 40907628 40257618 39787629 39547651 39437720
39317819 39507942=20


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ACUS11 KWNS 221818
SWOMCD
SPC MCD 221817=20
OKZ000-TXZ000-221945-

Mesoscale Discussion 0838
NWS Storm Prediction Center Norman OK
0117 PM CDT Mon May 22 2023

Areas affected...portions of the Oklahoma and Texas Panhandles into
far western Oklahoma.

Concerning...Severe potential...Severe Thunderstorm Watch likely=20

Valid 221817Z - 221945Z

Probability of Watch Issuance...80 percent

SUMMARY...Scattered thunderstorms are expected to develop in
proximity to a remnant MCV and surface trough this afternoon. Large
hail and damaging wind gusts are possible. A Severe Thunderstorm
Watch will likely be needed this afternoon.

DISCUSSION...As of 1815 UTC, visible satellite imagery showed
several area of agitated cumulus gradually deepening over the TX/OK
Panhandles in proximity to a remnant MCV and a weak surface pressure
trough. Early afternoon heating has removed most of the remnant
MLCINH across the region, with SPC mesoanalysis already showing
around 1000-1500 J/kg of MLCAPE in place. As the air mass continues
to warm, heating and subtle convergence along the aforementioned
surface features should result in thunderstorm development by
19-20z.

Mid-level flow is somewhat enhanced to the south of the MCV across
the southern and eastern Panhandles. Backed low-level flow was also
aiding in locally elongating area hodographs. As storms develop this
afternoon, 30-35 kt of effective shear should support organized
multicells and a few supercells this afternoon. While not overly
steep, mid-level lapse rates near 7 C/km along the eastern fringe of
the EML will be sufficient to support large hail, especially with
more sustained rotating storms. Steeper low-level lapse rates will
also favor damaging outflow gusts. Hi-res guidance suggests storms
may eventually consolidate into a forward-moving cluster with a
locally greater risk for damaging winds later this evening. A Severe Thunderstorm Watch will likely be needed this afternoon to cover the
threat for large hail and damaging gusts.

..Lyons/Grams.. 05/22/2023

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!6S6gBWTGNY1qYWUHNUMsPFvPkTxoQX5FAjg9Zk1IzV4lLKM3VDX249Bgs6zuiCQXoOhmh9yVU= gHbeWeaO4O7diqqKL0$ for graphic product...

ATTN...WFO...OUN...LUB...AMA...

LAT...LON 36840039 36870121 36110159 34790185 33650189 33220157
33160035 33529985 33809965 35329972 36689995 36840039=20


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