Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue May 13 2025 21:59:12

AWUS01 KWNH 132159
FFGMPD
VAZ000-WVZ000-140300-

Mesoscale Precipitation Discussion 0266
NWS Weather Prediction Center College Park MD
558 PM EDT Tue May 13 2025

Areas affected...Western Virginia & Adj portions of Eastern WV...

Concerning...Heavy rainfall...Flash flooding likely

Valid 132200Z - 140300Z

SUMMARY...Significant flash flooding event starting to unfold
across central VA.

DISCUSSION...21z surface map depicts a highly confluent flow
strengthening a focus for very slow moving/stationary band with
training elements aligning into terrain.  As noted in MPD 265, an
eastward extension of the upper-level trof continues to sharpen
across SW to S VA, supporting lee-cyclogenesis in the vicinity of
ROA to FVX.  Earlier afternoon convection/moderate shield
precipitation has aided the strengthening of a surface ridge
extension through the northern Shenandoah Valley which further
helps to anchor the strengthening band of convective activity from
Nottoway to Augusta county, VA.  Surface Tds in the upper 60s to
lower 70s remain located along the southwestern gradient of the
warm conveyor belt, delineated well by warm status clouds in the
1.6um near IR channel.  Solid insolation across NC and southeast
VA shows a pocket of unstable air with an axis fo 2000 J/kg SBCAPE
along and south of the confluence band to maintain/focus the
convective development.

Recent Visible imagery, RADAR mosaic and lightning detection show
the strengthening/expanding nature to the entire convective line,
though the apex near the Blue Ridge continues to focus best
convergence due to the upslope.  Total PWats of 1.3-1.5" and flux
at the cloud base should support rates of 1.5"/hr, increased
duration will support 1.5-3hrs of duration with slow northward
propagation and may result in localized 3-4" totals by 01z,
maintaining flash flooding conditions, where locally significant
flooding remains possible with a spot or two of 5"+ possible (in
line with recent 90th percentile for WoFS 20-21z solutions.=20

Additionally, a band of scattered storms are lifting north with
the 700-500mb trof axis across SW VA toward the area, this will
expand the risk of flash flooding southwestward within the terrain
where heavy rainfall today has sizably reduced the FFG values
below 1"/hr and 1.5"/3hr.  As such, even as they pass fairly
quickly with 1-2" totals may trigger localized flash flooding
upstream, before potentially merging with the line and finally
ejecting it more northeast into more stable air near and north of
the Potomac River Valley.

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!44aKQ3CFTO1oae-1CEiijb2JyLhnRDWqepZb9dSY0U689bxvzkJy87DSyFsUXdVLq7IL=
KkpZWdHx4UGkz0S2VliX13o$  for graphic product...

ATTN...WFO...AKQ...LWX...RNK...

ATTN...RFC...MARFC...SERFC...NWC...

LAT...LON   39047869 39037806 38587754 38067742 37607751=20
            37197762 37027792 37197853 37287912 37327958=20
            37477997 37887990 38347956 38717925=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to
https://lists.illinois.edu and use the "Unsubscribe" link.  Otherwise email
Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.20-Linux
 * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

.