Quantitative Precipitation Forecast
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FOUS30 KWBC 201459
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1058 AM EDT WED JUL 20 2016

...VALID 15Z WED JUL 20 2016 - 12Z THU JUL 21 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SW SAR 25 NNW SET 15 WNW MQB 15 ESE IOW 10 WNW MXO 20 N DBQ
FEP 10 WNW PNT 15 ESE DEC 15 E SLO MDH 20 SW SAR.


...20/1500Z UPDATE...

GIVEN THE CURRENT RADAR/SATELLITE TRENDS THIS MORNING...DECIDED TO
INTRODUCE A SLIGHT RISK ACROSS MUCH OF WESTERN IL EXTENDING BACK
INTO FAR EASTERN IA. THIS CONVECTION HAS FOCUSED ALONG A
NORTH/SOUTH LINE WITH CONTINUED RE-DEVELOPMENT ENHANCING THE
THREAT FOR FLASH FLOODING. THE 12Z RAOBS SHOWED THE ACTIVITY
DEVELOPING ALONG A TIGHT INSTABILITY GRADIENT...DAVENPORT IA 1100
J/KG RELATIVE TO SPRINGFIELD IL 87 J/KG. INTENSE HEAVY RAINFALL
HAS ALREADY OCCURRED WITH MACOMB IL NEARLY RECEIVING 1.75 INCHES
OF RAIN IN ONE HOUR BETWEEN 12-13Z. MULTI-HOUR RADAR LOOPS HAVE
SHOWN THE ACTIVITY DRIFTING EASTWARD INTO A REGION OF MUCH MORE
STABLE AIR ACROSS CENTRAL IL WHERE CONVECTIVE DEBRIS IS PRESENT.
THE 19/0000Z OU-CAPS ENSEMBLE SOLUTIONS HAVE HANDLED THIS ACTIVITY
RATHER WELL WITH THE COMPLEX CONTINUING TO SHIFT SOUTH AND EAST
WITH GRADUAL WEAKENING. THIS SEEMS REASONABLE GIVEN THE
AFOREMENTIONED STABLE AIR MASS DOWNSTREAM. THE THREAT FOR FLASH
FLOODING SHOULD CONTINUE DURING THE FIRST FEW HOURS OF THE OUTLOOK
PERIOD AS OUTLINED IN THE MESOSCALE PRECIPITATION DISCUSSION...MPD
#0479.

ELSEWHERE ON THE MAP...MAINTAINED THE SEE TEXT OVER THE UPPER
MIDWEST FOR THE POTENTIAL FOR ACTIVE CONVECTION DURING THE
OVERNIGHT HOURS. MODEL SPREAD REMAINS HIGH WITH SOME FAIRLY
EXTREME SOLUTIONS STILL IN THE MIX...PARTICULARLY THE 00Z CAMS.

RUBIN-OSTER


PREVIOUS DISCUSSION...

THE NUMBER OF MODELS/ENSEMBLE MEMBERS PRODUCING HEAVY RAINFALL IS
DROPPING WITH TIME.  A FEW OF THE HIGH RES RAPID REFRESH MEMBERS
0-4Z STILL INITIATED HEAVY SHOWERS/STORMS COMING ACROSS SOUTHERN
MN AND MOVED THEM INTO ADJACENT SOUTHERN WI OR IOWA.  AMONG THE
MAJOR CONVECTIVE ALLOWING ENSEMBLES THE 00Z RUN OF THE NSSL WRF
REMAINS THE HOLDOUT SHOWING HEAVY RAIN THIS MORNING OVER THE
REGION.  CONSEQUENTLY...THE AREA WILL BE MONITORED FOR POSSIBLE
CONVECTIVE DEVELOPMENT THIS MORNING.

OTHERWISE...THE MODELS ARE SHOWING LITTLE IN THE WAY OF A DEFINED
UPPER DIVERGENCE/LOWER CONVERGENCE SIGNAL TO TRIGGER SUSTAINED
SHOWERS/STORM DEVELOPMENT. THE OVERNIGHT RAP ANALYSIS SHOWS WEAK
300 MB DIVERGENCE MAXIMA THAT HAVEN`T BEEN ENOUGH TO GENERATE
CONVECTIVE DEVELOPMENT IN SOUTHERN MN.
PLENTIFUL MOISTURE REMAINS IN PLACE AS NOTED BY THE LAYER RELATIVE
HUMIDITY OF 70 PERCENT IN EASTERN IOWA...THERE IS UNCERTAINTY AS
TO WHETHER A STRONG ENOUGH ASCENT TO TRIGGER CONVECTIVE
DEVELOPMENT WILL DEVELOP OVER THE TOP OF THE CENTRAL US RIDGE. THE
300 MB DIVERGENCE IN LAST NIGHTS FORECASTS IS NOT PRESENT IN
TONIGHT`S FORECASTS.

PETERSEN
$$





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