Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 211354
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
954 AM EDT MON JUL 21 2014

...VALID 15Z MON JUL 21 2014 - 12Z TUE JUL 22 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 N K7L2 15 SSE BIS BIS 20 N BIS 40 N BIS 25 SW K5H4
10 SSW K5H4 15 ESE K5H4 20 N K46D 30 SE DVL 25 WSW RDR
15 SSE GFK 15 ESE CKN 15 NNE FSE 25 N BJI 20 NW FOZ ORB
20 NW ELO 20 NE ELO 30 WNW CKC 15 ESE GNA 40 SE GNA 45 NNE IWD
30 NNE IWD 20 NNE IWD 25 NW IWD 25 SE TWM COQ BRD 15 WSW SAZ
20 ESE FFM 20 WSW FFM 25 E KGWR KGWR 10 WNW K2D5 45 SSW JMS
35 ENE K7L2 20 NE K7L2 15 N K7L2.



...EASTERN ND INTO NORTHERN MN...

NO CHANGE MADE TO THE PREVIOUS SLIGHT RISK AREA IN THE UPPER
MIDWEST.  12Z RAOBS AND BLENDED TPW PRECIPITABLE WATER IMAGERY
SHOWED ONE AREA OF DEEPER MOISTURE PULLING OUT TOWARDS THE GREAT
LAKES...BUT LOW LEVEL WIND FIELDS ARE BEGINNING TO BACK AND DRAW
MORE MOISTURE NORTHWARD ACROSS THE EASTERN DAKOTAS.  THE AREA OF
CIN SHOWN BY THE 10Z/11Z HRRR ROUGHLY MATCHES THE H70 PROXY FOR A
CAP OF 12 DEG C IN THE 12Z SOUNDINGS SO NOT MUCH THREAT FOR
EXCESSIVE RAINFALL IS EXPECTED UNTIL LATE THIS AFTERNOON AT THE
EARLIEST.

PREVIOUS DISCUSSION...SIGNIFICANT CONVECTIVE/MCS DEVELOPMENT
EXPECTED THRU THIS REGION LATER MONDAY AFTERNOON AND NIGHT AS H5
S/WV ENERGY TURNING MORE EASTWARD OUT OF THE GREAT BASIN/NORTHERN
ROCKIES REACHES THE NORTHERN PLAINS LATER THIS AFTERNOON AND
CONTINUES THRU THE UPPER MS VALLEY MONDAY NIGHT.  SURFACE LOW
PRESSURE PULLING OUT OF THE DAKOTAS INTO MN LATER MONDAY AFTERNOON
INTO MONDAY NIGHT ALONG WITH A COLD FRONT DROPPING SLOWLY
SOUTHEASTWARD THRU THE REGION SHOULD FOCUS THE CONVECTION..WITH AN
INCREASING SOUTHWESTERLY LOW LEVEL JET BRINGING HIGHER MOISTURE
INTO THE SYSTEM AND WITH PWS EVENTUALLY FORECAST TO POOL TO NEAR
OR SLIGHTLY ABOVE 2 INCHES VICINITY OF THE SURFACE BOUNDARY.  IN
GENERAL..ALL OF THE MODEL QPF GUIDANCE IS INDICATING A HEAVY TO
VERY HEAVY RAINFALL EVENT..ALTHOUGH THERE CONTINUE TO BE SOME
MOSTLY LATITUDE DIFFERENCES ON JUST WHERE THE HEAVIEST RAINS WILL
OCCUR.  THE UKMET..CANADIAN AND NAM MODELS WERE CONSIDERED NORTH
AND WEST OUTLIERS WITH THE HEAVIEST RAINFALL AXIS..WHILE THE GFS
SEEMS TO BE SUFFERING FROM FEEDBACK PROBLEMS AND WAS NOT STRONGLY
CONSIDERED.  THE SUITE OF HIRES QPF GUIDANCE..INCLUDING THE
ARW..NMMB AND NSSL WRF WERE THE PREFERRED SOLUTIONS WITH THE
HEAVIER RAINFALL AXIS A LITTLE FARTHER SOUTH AND EAST..WITH THE
OLD ECMWF HIRES ALSO IN THIS CAMP.  VERY HIGH MOISTURE AND INTENSE
RAINFALL RATES WILL SUPPORT SOME ISOLATED 1-2 INCH RAINFALL
AMOUNTS IN A COUPLE OF HOURS..WITH SOME 2-3+ INCH TOTALS THIS
ENTIRE PERIOD LIKELY WITHIN THE THREAT AREA..IN SPITE OF WHAT
SHOULD BE A GENERALLY FORWARD PROPAGATING SYSTEM.  THESE RAINFALL
RATES/AMOUNTS COULD CAUSE SOME ISOLATED FLOODING PROBLEMS WITHIN
THE THREAT AREA.

...SOUTHEAST UNITED STATES...

12Z SOUNDINGS SHOWED A MOIST AIRMASS IN PLACE WITH PRECIPITABLE
WATER VALUES APPROACHING 2.25 INCHES IN THE CAROLINAS...AND K
INDEX VALUES OF 35 TO 40 SUGGESTING THE ENVIRONMENT CAN SUPPORT
LOCALLY HEAVY RAFL.  SOME ISOLATED PROBLEMS DUE TO RUNOFF OR
PONDING OF WATER MAY BE POSSIBLE FROM THE CAROLINAS INTO SOUTHWEST
VA SINCE ANY CELLS CAPABLE OF PRODUCING MDT TO LOCALLY HEAVY
RAINFALL SHOULD BE MOVING FAIRLY SLOW GIVEN SPEEDS OF UNDER 10 KTS
IN THE STEERING LAYER.  THINKING IS THAT THE MOST LIKELY TIME FOR
PROBLEMS SHOULD BE CONFINED TO THE PERIOD FROM LATE THIS AFTERNOON
INTO THE EARLY EVENING.

TERRY/BANN






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