MESOSCALE PRECIPITATION DISCUSSION 0423
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
305 PM EDT SAT JUL 01 2017

AREAS AFFECTED...EASTERN PA...NORTHERN NJ...CENTRAL/EASTERN
NY...VT...NH...WESTERN CT...CENTRAL/WESTERN MA...WESTERN ME

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 011900Z - 020000Z

SUMMARY...NUMEROUS CLUSTERS OF SHOWERS AND THUNDERSTORMS THIS
AFTERNOON WILL AGAIN PRODUCE LOCALLY HEAVY RAINFALL TOTALS. GIVEN
THE WET ANTECEDENT CONDITIONS...FLASH FLOODING WILL BE LIKELY.

DISCUSSION...REGIONAL DUAL-POL RADAR IMAGERY SHOWS NUMEROUS
CLUSTERS OF HEAVY SHOWERS AND THUNDERSTORMS DEVELOPING AND
CONTINUING TO EXPAND IN COVERAGE OVER INTERIOR AREAS OF NY AND NEW
ENGLAND...WITH SOME OF THE STRONGEST ACTIVITY NOTED IN A CLUSTER
NORTH OF ALBANY NEAR GLEN FALLS WHICH IS EDGING INTO CENTRAL VT. A
SECOND CLUSTER OF RELATIVELY INTENSE ACTIVITY IS SEEN FARTHER BACK
TO THE SOUTHWEST BACK IN BETWEEN SYRACUSE AND ITHACA. IN BOTH
CASES THE CLOUD TOPS HAVE TENDED TO COOL A BIT FURTHER OVER THE
LAST HOUR AS SEEN IN THE LATEST EXPERIMENTAL GOES-16 10.3
MICRON/IR IMAGERY.

THE CONVECTION CONTINUES TO BE FAVORED ON THE LARGE SCALE BY THE
EASTWARD ADVANCE OF AN UPPER LEVEL TROUGH MOVING ACROSS THE UPPER
OH VALLEY AND LOWER GREAT LAKES REGION. ON THE SMALLER
SCALE...EXPERIMENTAL GOES-16 6.9 AND 6.2 MICRON/WV IMAGERY SHOWS A
SSW/NNE AXIS OF SHORTWAVE ENERGY PRECEDING THE MAIN UPPER TROUGH
EXTENDING FROM THE MD/WV PANHANDLES UP ACROSS CENTRAL PA AND INTO
WEST-CENTRAL NY. THIS IS STRONGLY FACILITATING THE SECONDARY BATCH
OF CONVECTION OVER PARTS OF SOUTHWEST AND SOUTHERN NY ALONG WITH
THE BROADER NORTHERN MID-ATLANTIC AS IT IS ALSO ENCOUNTERING A
MODERATELY UNSTABLE AND VERY MOIST AIRMASS AHEAD OF IT. PWATS OF
OVER 1.75 INCHES ARE CONTRIBUTING TO AN ENVIRONMENT CONDUCIVE FOR
ENHANCED RAINFALL RATES...AND GIVEN THE INSTABILITY...SOME RATES
MAY APPROACH 2.5 INCHES/HR IN SOME CASES.

STRONG DIURNAL HEATING/MOISTURE TRANSPORT AHEAD OF THE SHORTWAVE
ENERGY AND LARGER SCALE TROUGH COUPLED WITH PRESENCE OF A SURFACE
TROUGH OVER THE INTERIOR OF NY/PA AND INTERIOR NEW ENGLAND ALONG
DIFFERENTIAL HEATING BOUNDARIES WILL ALLOW CONVECTION TO CONTINUE
TO DEVELOP AND BECOME A BIT BETTER ORGANIZED THROUGH THE AFTERNOON
ACROSS MUCH OF THE NORTHEAST.

EXPECT ADDITIONAL CONCERNS FOR FLASH FLOODING...ESPECIALLY OVER
AREAS OF CENTRAL/EASTERN NY AND INTO NORTHERN NEW ENGLAND
INCLUDING VT/NH AND POSSIBLY PARTS OF WESTERN ME WHERE RECENT
HEAVY RAINFALL HAS SATURATED THE GROUND...AND THUS ANY ADDITIONAL
RAIN WILL ENCOURAGE SIGNIFICANT RUNOFF AND FLASH FLOODING.
ADDITIONAL RAINFALL TOTALS OF 3 TO 5 INCHES WILL BE POSSIBLE
ACROSS THESE AREAS.

THE THREAT OF FLASH FLOODING IS A BIT MORE MARGINAL FARTHER SOUTH
OVER THE NORTHERN MID-ATLANTIC...BUT INTENSE RAINFALL RATES HERE
MAY CAUSE SOME LOCALIZED PROBLEMS AND ESPECIALLY NEAR URBANIZED
AREAS. RAINFALL AMOUNTS HERE MAY OF UP TO 2 TO 3 INCHES WITH
ISOLATED HEAVIER AMOUNTS WILL BE POSSIBLE.

ATTN...WFO...ALY...BGM...BOX...BTV...CTP...GYX...LWX...OKX...
PHI...

ATTN...RFC...MARFC...NERFC...

LAT...LON   45246990 44606919 43457034 42317164 41327297
            40697367 39967473 39707621 39787699 40127710
            40787676 41427647 42417604 43017535 43507434
            44467287 45057131