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WPC Met Watch

 
Mesoscale Precipitation Discussion: #0255 (2022)
(Issued at 940 AM EDT Thu May 26 2022 )

MPD Selection
 


Graphic for MPD #0255

Mesoscale Precipitation Discussion 0255
NWS Weather Prediction Center College Park MD
940 AM EDT Thu May 26 2022

Areas affected...FL Panhandle...Coastal AL...

Concerning...Heavy rainfall...Flash flooding possible

Valid 261339Z - 261929Z

SUMMARY...Repeated thunderstorm development will maintain heavy
rainfall over portions of the AL Gulf Coast into the Florida
Panhandle this morning.

DISCUSSION...Multiple clusters of thunderstorms continued over the
Florida Panhandle and AL Gulf Coast this morning. The first band
of thunderstorms was oriented along a 925-850 mb confluence zone
toward PAM to AAF, and gradually advecting northward within the
plume given 20 kts of 850-300 mean flow. Upstream of this
activity, GOES-16 IR imagery shows an area of cooling cloud tops
developing to the south as thunderstorms backbuild atop a local
instability maxima. Additional thunderstorms were starting to fill
in across the AL/FL border region back toward the approaching cold
frontal convection.  This is associated more with periphery of the
approaching 500 mb height-falls supporting deeper southwesterly
flow and therefore northeastward propagation ahead of the front. 

Instability along the coast remains the main uncertainty over the
next few hours, with RAP mesoscale analysis depicting a tight
SBCAPE and PWAT gradient which slowly advect inland with time.
RADAR and IR trends suggest the instability is still offshore in
the highlighted area; however, recent trends, particularly further
west suggest that advection is starting to manifest.  Expectation
is for the highlighted area destabilize as forecast, enhancing
cores of thunderstorms to support rain rates in excess of 2"/hr.
Moreover, surface based convection would enhance rain rates via
dynamic ascent, given low-level hodograph curvature noted along
the coastline. The eventual merger of the two bands coupled with
frictional convergence along the coast should also locally enhance
moisture convergence and therefore enhance rainfall efficiency
with potential for localized 3"/hr rates, as has been the case for
the last day or so.

Flash flooding concerns will continue as these cells witll cross
areas that have seen on average over 2" with scattered pockets of
4-7" over the last 24 hours making coastal locations susceptible
to flooding from any additional rainfall. This is corroborated by
a widespread area of 95-100% 0-40 cm soil moisture ratios along
the coast, per NASA SPoRT. As such, expect a continued threat of
heavy rain and flooding until the cold front passes through later
this afternoon...but given the uncertainty of placement or even
magnitude coming ashore flash flooding/rapid inundation remains
possible.   

Asherman/Gallina

ATTN...WFO...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON   31418746 31248564 30818477 30298416 29868430
            29478521 29878587 30058713 30078815 30928833
           


Last Updated: 940 AM EDT Thu May 26 2022
 

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Page last modified: Thursday, 12-May-2022 19:44:52 GMT