WPC Met Watch |
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Mesoscale Precipitation Discussion: #0344 (2017) |
(Issued at 437 PM EDT MON JUN 19 2017
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MPD Selection |
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MESOSCALE PRECIPITATION DISCUSSION 0344
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
437 PM EDT MON JUN 19 2017
AREAS AFFECTED...NERN PA...NRN NJ...SERN NY...WRN CT...WRN
MA...SRN VT...NH...ME
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 192037Z - 200200Z
SUMMARY...POTENTIAL FOR HIGH RAINFALL RATES AS WELL AS MULTIPLE
ROUNDS OF CONVECTION OVER THE SAME AREAS COULD RESULT IN 2-4"
RAINFALL AMOUNTS OVER SEVERAL HOURS. FLASH FLOODING IS POSSIBLE.
DISCUSSION...A HIGHLY MOIST AND MODERATELY UNSTABLE AIR MASS IS IN
PLACE ACROSS THE NORTHEAST THIS AFTERNOON AHEAD OF AN INCOMING
COLD FRONT AND HEIGHT FALLS ADVANCING INTO THE NORTHEAST AHEAD OF
AN UPPER LEVEL TROUGH. MLCAPE VALUES RANGING FROM 1000-2000 J/KG
WERE INDICATED ON THE LATEST RAP MESOANALYSIS, WITH PWATS of
1.75-2.0" (2-3 STANDARD DEVIATIONS ABOVE AVERAGE). SURFACE DEW
POINTS IN THE LOWER 70S F WERE ADVECTING INTO NEW ENGLAND LATE
THIS AFTERNOON ON 10-20KT LOW-LEVEL SOUTHERLY FLOW AHEAD OF THE
FRONT, SUPPORTING LOW LCLS (NEAR 1000 M) AND A RELATIVELY DEEP
WARM CLOUD LAYER DEPTH EXCEEDING 4 KM. THE RESULT IS THE POTENTIAL
FOR HIGH PRECIPITATION EFFICIENCY AND HEAVY RAINFALL RATES IN ANY
ROBUST CONVECTION THAT OCCURS. CURRENT RADAR ESTIMATES SHOW
RAINFALL RATES IN THE 1-2 IN/HR RANGE, WHICH IS ON PAR WITH FFG
VALUES OVER MUCH OF THE REGION. WHILE THE CURRENT FLOW SETUP IS
NOT OVERLY CONDUCIVE FOR SIGNIFICANT BACKWARD PROPAGATION, THERE
IS THE POTENTIAL FOR MULTIPLE ROUNDS OF HEAVY RAINFALL ACROSS THE
SAME AREAS THROUGH THE NEXT SEVERAL HOURS.
THE LATEST HRRR AND HRRR-EXPERIMENTAL RUNS SEEM TO HAVE A DECENT
HANDLE ON THE ONGOING CONVECTION. THERE IS A GENERAL CONSENSUS
AMONG MUCH OF THE HIGH-RES GUIDANCE (HRRR, HRRR-EXPERIMENTAL,
WRF-NSSL, AND THE ARW) ON PORTIONS OF THE OUTLINED AREA RECEIVING
AN ADDITIONAL 2-4 INCHES OF RAINFALL THROUGH 02Z. THERE IS SOME
SPREAD AS TO EXACTLY WHERE THE HEAVIEST AMOUNTS WILL FALL DUE TO A
COMPLEX INTERACTION AMONG MULTIPLE BOUNDARIES/COLD POOLS AND THE
COLD FRONT. FLASH FLOODING IS POSSIBLE THROUGH 02Z.
RYAN
ATTN...WFO...ALY...BGM...BOX...BTV...CAR...GYX...OKX...PHI...
ATTN...RFC...MARFC...NERFC...
LAT...LON 46966922 46926834 46616809 46146827 45536870
44516964 43477080 42037206 41477263 40987317
40437381 40127442 40057502 40187555 40607573
41037528 41337493 41707445 42077419 42437389
42997371 43577332 44137283 44667222 45297131
46527018
Last Updated: 437 PM EDT MON JUN 19 2017
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