250
AWUS01 KWNH 040251
FFGMPD
CTZ000-NYZ000-NJZ000-PAZ000-040830-
MESOSCALE PRECIPITATION DISCUSSION 1192
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1050 PM EDT THU SEP 03 2026
AREAS AFFECTED...SOUTHERN UPSTATE NY & NYC/LONG ISLAND...NORTHEAST
PA...NORTHERN NJ...SOUTHWEST CT...
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 040250Z - 040830Z
SUMMARY...NARROW BAND OF REPEATING CELLS THROUGH SATURATED AREAS
POSE POSSIBLE INCIDENTS OF LOCALIZED FLASH FLOODING EVEN WITH
SCATTERED 1-3" TOTALS OVERNIGHT.
DISCUSSION...GOES-E WV SUITE DEPICTS A EMBEDDED SHORTWAVE FEATURE
ACROSS NORTHWEST PA SLIDING EASTWARD THOUGH DEEPER UNIDIRECTIONAL
WNW FLOW REGIME. THIS WAVE IS SUPPORTED BY RIGHT ENTRANCE TO 90KT
SPEED MAX OVER CENTRAL UPSTATE NY AIDING VERTICAL ASCENT PATTERN
ALONG THE CONVERGENT NORTHERN ROTOR OF THE SHORTWAVE FEATURE. IN
THE LOW TO MID-LEVELS, RAP CONTINUES TO SHOW A WEAKLY BUOYANT
ENVIRONMENT REMAINS IN PLACE ALONG THE NY/PA BORDER EXTENDING INTO
THE LOWER HUDSON VALLEY WITH 500-1000 J/KG OF UNCAPPED MLCAPE
ALONG AND DOWNSTREAM OF THE MID-LEVEL FORCING.
WHILE THE FORCING AND BUOYANCY ARE NOT PARTICULARLY STRONG, THERE
REMAINS MODEST ELEVATED MOISTURE FLUX CONVERGENCE ALONG A
TIGHTENING MOISTURE GRADIENT (DENOTED IN PWAT FIELD). POOL OF
1.75" ACROSS SW UPSTATE NY INTO NORTHERN PA REMAINS IN PROXIMITY
TO ASCENT AXIS THOUGH VALUES DROP OFF TO BELOW 1.3" ACROSS THE
MOHAWK VALLEY THROUGH NORTHEAST CT. SO INFLUX FROM THE SOUTH AND
SOUTHEAST SHOULD PROVIDE CAPABILITY FOR EFFICIENT RAINFALL
PRODUCTION DUE TO FLUX CONVERGENCE, THOUGH UPDRAFTS SHOULD BE
NARROW. STILL, IN STRONG WNW FLOW REGIME WITH 20-25KTS OF
850-700MB FLOW FROM THE WEST, SHOULD ALLOW FOR BACK-BUILDING OR
UPSTREAM REGENERATION EVEN AS NEW DEVELOPMENT BREAKS OUT
DOWNSTREAM TOWARD THE POCONOS/CATSKILLS OVER THE NEXT FEW HOURS
(AND FURTHER DOWNSTREAM INTO THE LOWER HUDSON VALLEY). RATES TO
1.5"/HR ARE POSSIBLE THOUGH THAT COVERAGE IN INTERSECTION OF
RAINFOOT ACROSS MULTIPLE UPPER REACHES OF WATERSHEDS NEEDED FOR
BROADER FLASH FLOODING MAY BE MORE LIMITED.
THE GREATER CONCERN IS THAT EFFICIENT WARM CLOUD PROCESSES WILL
FALL OVER AREAS RECENTLY COMPROMISED WITH MULTIPLE ROUNDS OF HEAVY
RAINFALL SATURATING THE UPPER SOIL PROFILES AS MUCH OF THE AREA
ALONG AND SOUTH OF THE NY/PA LINE INTO SE NY ARE RUNNING WELL
ABOVE NORMAL IN THE 90TH TO 99TH PERCENTILES AROUND 65-80% RATIOS.
AS SUCH, FFG VALUES ARE SIGNIFICANTLY REDUCED TO LESS THAN 1"/HR
ACROSS A LARGE PORTION OF THE AREA OF CONCERN WITH SOME SPOTS
BELOW .5"/HR. THREE TO SIX HOUR FFG ARE NOT MUCH BETTER WITH
BROAD AREAS BELOW 1.5". GIVEN NARROW STREAKS OF 1-3" AND
SCATTERED/SMALL AREAL COVERAGE CONFIDENCE IN FLASH FLOODING
CONDITIONS SUGGEST POSSIBLE INCIDENTS MORE THAN HIGH/LIKELY
CONFIDENCE.
GALLINA
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...ALY...BGM...BUF...CTP...OKX...PHI...
ATTN...RFC...RHA...TAR...NWC...
LAT...LON 42897689 42307505 41517314 41187228 40907229
40637301 40457406 41057574 41727733 42167810
42497844 42847817
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page