Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 020844
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
444 AM EDT WED SEP 02 2015

...VALID 12Z WED SEP 02 2015 - 12Z THU SEP 03 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...



...UPPER MISSISSIPPI VALLEY...

LATEST SATELLITE IR/WV LOOPS SHOW CONTINUED COMPACT MCS
DEVELOPMENT ACROSS THE UPPER MS VALLEY...OUT AHEAD OF A
WELL-DEFINED SHORTWAVE CURRENTLY PROGRESSING THROUGH EASTERN SD
AND NORTHERN NE. THE COMPACT AREA OF UPPER LEVEL FORCING (UPPER
DIVERGENCE) IS INTERSECTING A THERMODYNAMICALLY-RICH
ENVIRONMENT...WITH MUCAPES ON THE ORDER OF 2000-3000 J/KG...PWS OF
1.5-1.75 INCHES...AND A LOW LEVEL JET PEAKING AROUND 25-35 KTS
ABOVE THE DECOUPLED LAYER (~925 MB). THESE PARAMETERS WILL LIKELY
MAINTAIN THE CURRENT MCS STRUCTURE THROUGH THE EARLY AM
HOURS...WITH THE STRENGTH/DEPTH OF THE INSTABILITY CAPABLE OF
INTENSE RAINFALL RATES ON THE ORDER OF 2+ INCHES PER HOUR OVER
ISOLATED AREAS PER THE RECENT RADAR ESTIMATES. AS A
RESULT...LOCALIZED SHORT TERM RUNOFF ISSUES ARE ANTICIPATED
CONSIDERING THE CURRENT FFG VALUES.

DO EXPECT A DIMINISHING TREND LATER THIS MORNING FOLLOWING THE
DECAY OF THE LOW-LEVEL JET...HOWEVER...THE MODELS (ESPECIALLY THE
MESOSCALE GUIDANCE) REMAIN RATHER ROBUST WITH RE-DEVELOPMENT LATER
IN THE DAY WITH PEAK HEATING OUT AHEAD OF THE SLOW MCV
TRACK...THOUGH BELIEVE THE MAJORITY OF THE GUIDANCE ARE TOO FAR
NORTH WITH THE HEAVIER QPF. BASED ON THE CURRENT TRENDS AND
ANTICIPATED AREA OF BEST DESTABILIZATION BY AFTERNOON (I.E. LESS
MCS DEBRIS TO OVERCOME)... FEEL THE BEST CHANCE FOR LOCALIZED
EXCESSIVE RAINFALL WILL BE ACROSS CEN/SRN WI INTO NORTHERN IL. THE
ONLY MODEL THAT SEEMS TO BE CAPTURING THIS IDEA AT THIS POINT IS
THE 00Z SPCWRF (WHILE KEEPING IN MIND ITS HIGH BIAS).

HURLEY

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