WPC Met Watch |
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Mesoscale Precipitation Discussion: #0859 (2020) |
(Issued at 1115 PM EST Wed Nov 11 2020
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MPD Selection |
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Mesoscale Precipitation Discussion 0859
NWS Weather Prediction Center College Park MD
1115 PM EST Wed Nov 11 2020
Areas affected...Mid-Atlantic
Concerning...Heavy rainfall...Flash flooding likely
Valid 120415Z - 121015Z
SUMMARY...Areas of showers and thunderstorms will continue through
the overnight hours with heavy rainfall rates. Given some of the
earlier heavy rainfall, and tendencies for some of the convection
to train over the same area, some areas of flash flooding will
continue to be likely.
DISCUSSION...Bands of heavy showers and thunderstorms continue to
develop and lift off to the northeast across areas of central and
western NC, much of VA, the Delmarva, and southern NJ. The
activity continues to focus within an extremely moist airmass for
this time of the year across much of the Mid-Atlantic and
Southeast as a pool of deep tropical moisture has enveloped this
region ahead of a cold front approaching the Appalachians, and
with the aid of deep layer southerly flow along the East Coast
situated in between T.S Eta over the northeast Gulf of Mexico, and
a strong subtropical ridge over the western Atlantic Ocean. In
fact, the PWs are locally on the order of 2.0 to 2.25 inches which
is in the 95th to 99th percentile of climatology for the middle of
November.
This moisture is coupling with a broad area of instability
characterized by MUCAPE values on the order of 500 to 1000+ k/kg,
which is also quite impressive for this of the year, in
conjunction with relatively robust right-entrance region upper jet
dynamics to facilitate the larger scale coverage of convection.
Additionally, there are pockets of locally focused surface
convergence which coupled with a southerly low-level jet of 30+
kts is allowing for these bands of convection to remain quite
sustainable.
Rainfall rates are locally as much as 1 to 2 inches/hr, and some
of the bands of convection have been tending to be aligned with
the deeper layer mean flow which is fostering some training of
these cells. Already some areas across western NC, and southwest
to central VA have seen 2 to 4 inches of rain today, and the
latest 00Z hires model consensus suggests another 2 to 4 inches of
rain may be locally possibly going through the remainder of the
night. The heaviest rainfall is likely to focus in areas from
central VA northeastward across southern MD and the Delmarva.
Given the additional rainfall potential and wet antecedent
conditions, some additional areas of flash flooding will be likely
overnight.
Orrison
ATTN...WFO...AKQ...GSP...LWX...PHI...RAH...RNK...
ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...
LAT...LON 39307505 39037456 38587476 38197520 37727620
36617882 35528061 35258169 35468205 36258173
37567999 38407838 38797713
Last Updated: 1116 PM EST Wed Nov 11 2020
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