Mesoscale Precipitation Discussion 905
NWS Weather Prediction Center College Park MD
1153 PM EDT Thu Sep 27 2018

Areas affected...Western VA...Northeast WV...West-central
MD...Eastern PA...Northern PA...Southeast NY

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

Valid 280352Z - 280902Z

Summary...Widespread moderate rain with numerous embedded
convective cells is expected across the central Appalachians and
adjacent eastern Piedmont region of the Mid-Atlantic through the
early morning hours.  Wet antecedent conditions increases the
concern for flooding issues and enhanced run-off.

Discussion...Regional Doppler radar imagery indicates a widespread
area of moderate to heavy rain progressing from southwest to
northeast across the Mid-Atlantic region. Embedded convection is
also present and these cells are producing rainfall rates in
excess of an inch per hour.  GOES-16 infrared satellite imagery is
depicting vigorous convection across southwest Virginia and into
north-central North Carolina, and this activity will be making its
way across central and western Virginia through 2 am and then
weakening some as it reaches eastern Pennsylvania and New Jersey.

The latest surface analysis depicts a wave of low pressure
situated along a quasi-stationary front near the VA/NC border. 
Large scale ascent is being aided by a shortwave trough
approaching from the Ohio Valley and right entrance upper level
jet dynamics in place.  Anomalous levels of moisture are also in
place with PWs on the order of 1.5 to 2 inches.

Recent high res model runs are indicating the potential for swaths
of 1 to locally 3 inches of rain by 5 am local time.  Many areas
across eastern West Virginia and western Virginia have already
received rainfall amounts near or above two inches in the past 24
hours alone, and this has lowered flash flood guidance values
significantly, in many cases under 1.5 inches in 3 hours, and
flash flooding is possible with the heaviest rainfall.

D. Hamrick

ATTN...WFO...AKQ...ALY...BGM...CTP...LWX...OKX...PBZ...PHI...
RLX...RNK...

ATTN...RFC...MARFC...NERFC...OHRFC...SERFC...

LAT...LON   42057421 41657371 41137356 40777369 40407405
            39987483 39677559 39317619 38887673 38397722
            37607769 36967806 36677847 36627901 36647948
            36817987 37078013 37458021 38227999 39507893
            40657748 41577597 42007497