Mesoscale Precipitation Discussion 0226...Corrected
NWS Weather Prediction Center College Park MD
323 PM EDT Mon May 05 2025

Corrected for spelling error in areas affected headline

Areas affected...portions of northern Mid-Atlantic and central
Appalachians to Lake Erie

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

Valid 051846Z - 060045Z

SUMMARY...Training of showers and thunderstorms from the northern
mid-Atlantic and central Appalachians to the southern shore of
Lake Erie may result in isolated to widely scattered areas of
flash flooding through the early evening. Rainfall rates of 1-2
in/hr are expected.

DISCUSSION...Visible satellite and regional radar imagery from
1830Z showed scattered showers and thunderstorms extending from
northern VA into northern MD, northwestward into PA, western NY
and eastern OH. These showers/storms were located northeast of a
closed mid to upper-level low over the OH Valley with low level
southeasterly flow advecting moisture northwestward across the
region. Broadly diffluent flow aloft was in place to the northeast
of the closed low, helping increase synoptic scale lift over the
region. Blended TPW imagery showed that PW values ranged from ~1.4
inches to the southeast over northern MD to ~0.7 inches over
eastern OH. SPC mesoanalysis data from 18Z showed MLCAPE was
generally weak at 500-1000 J/kg with cloud cover or lower moisture
values limiting instability to some degree.

However, flash flood guidance values across a large portion of the
region were about 1.0 to 1.5 inch/hr or slightly less and
similarly oriented low level and mean steering flow wind vectors
were supportive of repeating cells. While 925-850 mb winds were
generally weaker than the mean steering flow, low level axes of
confluence will support lines of showers/thunderstorms with a
tendency for cell repeating and short term training. The
environment is supportive of 1-2 in/hr rainfall rates and some
indications from the RAP support a minor increase in the low level
flow toward 00Z which could help increase the threat for
backbuilding cells. The flash flood threat is expected to be
isolated to widely scattered in nature through 01Z.

Otto

ATTN...WFO...BUF...CLE...CTP...LWX...PBZ...RLX...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON   42437874 41107743 40007715 39257740 38697812
            38777907 39138020 39888046 40198103 40628153
            41728134 42258003