Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 190827
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
427 AM EDT WED APR 19 2017

...VALID 12Z WED APR 19 2017 - 12Z THU APR 20 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 S BJJ 10 W MFD 30 ENE FDY 20 E TDZ 15 ESE CXPT 30 NNE CGF
10 SSE ERI 30 SSW JHW 25 W DUJ 20 WNW IDI 10 E PIT 15 NNW HLG
25 S BJJ.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ESE RZN 15 NNE PBH 15 E IMT 15 W CVX 30 SW APN 25 NNE MBS
10 NNW RNP 20 NNW BTL 10 SSE UGN 15 WNW SFY 10 WSW CID MIW
15 SSE CAV 10 NNE AXA 15 W MWM 10 ENE MML 15 W ILL 10 NNE 2P3
PNM 15 ESE RZN.


NORTHEAST OH INTO WESTERN PA

A MARGINAL RISK AREA WAS ADDED ACROSS NORTHEAST OHIO INTO WESTERN
PA.  CONCERN IS FOR A PERIOD OF TRAINING OF CELLS WEDNESDAY
EVENING INTO WEDNESDAY NIGHT ALONG THE COLD FRONT SINKING THROUGH
THE EASTERN LAKES.  THE LOW LEVEL FLOW AT THIS TIME IS EXPECTED TO
BE WESTERLY AND PARALLEL TO THE BOUNDARY---SUPPORTING THE
POTENTIAL FOR TRAINING OF CELLS-  IN AREA OF TRAINING---ISOLATED
RAINFALL TOTALS OF 1"+ IN AN HOUR MAY PRODUCE ISOLATED RUNOFF
ISSUES---ESPECIALLY IN URBANIZED REGIONS.

UPPER MS VALLEY TOWARD THE UPPER LAKES

NO SIGNIFICANT CHANGES WERE MADE TO THE PREVIOUS MARGINAL RISK
AREA OVER THE UPPER MS VALLEY TOWARD THE UPPER LAKES.  INCREASING
CONVECTION EXPECTED AS STRENGTHENING HEIGHT FALLS PUSH EAST
NORTHEASTWARD INTO THE CENTRAL TO NORTHERN PLAINS AND UPPER MS
VALLEY DAY 1 WITH STRONG ISENTROPIC LIFT EXPECTED AHEAD OF THE
ASSOCIATED DEVELOPING SURFACE LOW MOVING FROM THE CENTRAL PLAINS
INTO THE UPPER MS VALLEY. THE STRONGEST LOW LEVEL INFLOW/MOISTURE
FLUX AHEAD OF THE DEVELOPING LOW SUPPORTS MAX PRECIP TOTALS LATE
AFTERNOON/EVENING INTO THE OVERNIGHT HOURS FROM THE UPPER MS
VALLEY TOWARD THE UPPER LAKES.  THERE ARE SOME LATITUDE
DIFFERENCES IN THE MODELS WITH THE MAX QPF AXIS.  WPC QPF FAVORED
THE FARTHER SOUTH MAX AXIS OF THE CMC GEM--NSSL WRF AND ECMWF.
THIS HAS SUPPORT FROM THE GFS RE-FORECAST.  SIMULATED RADARS FROM
THE HI RES GUIDANCE SHOW POTENTIAL FOR A WELL DEFINED NORTH TO
SOUTH ORIENTED SQUALL LINE MOVING ACROSS THESE AREAS.  THEY
DO---HOWEVER---SHOW THIS CONVECTION REMAINING PROGRESSIVE---WHICH
MAY LIMIT VERY HEAVY TOTALS FROM OCCURRING.  STILL--WITH RAIN
RATES OF .50-1"+ PER HOUR POSSIBLE WITH THIS CONVECTIVE
LINE---ISOLATED RUNOFF ISSUES ARE POSSIBLE---ESPECIALLY IN
URBANIZED REGIONS.

ORAVEC
$$





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