Quantitative Precipitation Forecast
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314
FOUS30 KWBC 191448
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1047 AM EDT TUE JUL 19 2016

...VALID 15Z TUE JUL 19 2016 - 12Z WED JUL 20 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
SUT 40 NE CHS 15 SE MMT 30 W UDG HRJ RWI 20 WNW ECG 25 ENE FFA
30 NE HSE 25 E MRH SUT.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SW AXA 20 ESE OVL 15 SW OEO 30 ESE EAU 10 SSE EFT 10 ESE PIA
15 SSE EOK 15 WSW OTM 25 SW AXA.


19/1500Z UPDATE...

THE ONLY SIGNIFICANT CHANGE MADE TO THE OVERNIGHT OUTLOOK WAS TO
ACCOUNT FOR THE ONGOING CONVECTION ACROSS WESTERN/CENTRAL IA.
WHILE THE LEADING CONVECTIVE LINE HAS BEEN PROGRESSIVELY MOVING
INTO CENTRAL IA...ADDITIONAL THUNDERSTORMS CONTINUE TO DEVELOP IN
ITS WAKE ACROSS THE NORTHWESTERN IA WITH A GENERAL WEST-EAST
ORIENTATION. RECENT HOURLY RATES PER MESONET DATA REMAIN IN THE
0.75 TO 1.00 INCH RANGE. WHILE THERE MAY NOT BE A WIDESPREAD
THREAT FOR FLASH FLOODING...THIS EARLY ROUND OF CONVECTION WILL
EFFECTIVELY LOWER FFG VALUES ACROSS THE REGION. DIFFICULT TO SAY
HOW LONG THIS ACTIVITY WILL PERSIST GIVEN THE LIMITED INSTABILITY
POOL BASED ON RECENT RAP OBJECTIVE ANALYSES. HOWEVER...THERE SEEMS
TO BE SOME SORT OF WEST-EAST BOUNDARY THE CONVECTION IS FIRING
ALONG WHILE IN THE PRESENCE OF 1.75 TO 2.00 INCH PWATS.

RUBIN-OSTER


PREVIOUS DISCUSSION...

...CENTRAL PLAINS/MID-UPPER MS VALLEY...

THE MODELS INDICATE ACTIVITY IN NEBRASKA TRANSLATE DOWNSTREAM INTO
MN/IOWA AS THE LOW-MID LEVEL WARM FRONT AND ZONE OF 850-700 MB
WARM/MOIST ADVECTION AND CONVERGENCE SPURS CONVECTIVE DEVELOPMENT
TODAY AND TONIGHT.
LOCALLY HEAVY RAINFALL IS INDICATED AS THE GFS SHOWS PRECIPITABLE
WATER (PW) MAXIMA OF 2 INCHES INTO SOUTHEAST MN/ECMWF UP TO 2.25
INCHES NEAR THE SOUTHERN MN/WI BORDER.
THE HIGH RES WRF ARW AND NMMB/NAM CONUS NEST ALSO SHOW MAXIMA
DEVELOPING WITHIN THE WARM ADVECTION ZONE AND MOISTURE POOL IN
EASTERN IOWA...SUPPORTED BY THE NAM 300 MB DIVERGENCE SLIDING
SOUTHEAST OVERNIGHT FROM SOUTHEAST MN INTO EASTERN IOWA...AND THE
ECMWF INCREASING PW VALUES TO 2 INCHES. MANUAL PROGS BLENDED THE
GFS/NAM AND HIGH RES CONVECTIVE ALLOWING MODELS 00Z WRF
ARW/NMMB/NSSL WRF.  THE 00Z CANADIAN REGIONAL GEM MOVED THE PRECIP
EAST FASTER ACROSS WI/IL AND WAS GIVEN THE LEAST WEIGHTING AS AN
OUTLIER. A SLIGHT RISK OF EXCESSIVE RAINFALL WAS INDICATED AS THE
POSSIBILITY EXISTS OF MORE THAN ONE ROUND OF STORMS PLUS THE HIGH
RES CONVECTIVE ALLOWING ENSEMBLES SHOW POTENTIAL FOR 3-6 INCHES OF
RAIN FOR THE 24 HOUR PERIOD.


...SOUTHERN MID-ATL/SOUTHEAST...

AN UPPER-LEVEL TROUGH WILL DRIVE A SURFACE COLD FRONT THROUGH THE
SOUTHERN MID-ATL STATES INTO THE SOUTHEAST... WHILE BECOMING
QUASI-STATIONARY OR STALL. PRECIPITABLE WATER (PW) VALUES
GENERALLY 1.5 TO 2 INCHES WILL POOL OUT AHEAD AND INVOF OF THIS
FRONTAL ZONE...WHICH  LIKELY YIELDING SCATTERED TO NUMEROUS
SHOWERS/STORMS WITH THE MOST WIDESPREAD ACTIVITY TUE AFTN/EVENING
ACROSS SERN VA INTO ERN NC/NORTHEAST SC...WHERE THE SEA BREEZE
SHOULD AID DEVELOPMENT OF SHOWERS.  WITH THE 850 MB TROUGH
PROGRESSING SOUTH...THE ACTIVITY SHOULD MOVE SLOWLY SOUTH TONIGHT.
MANUAL PROGS BLENDED CONTINUITY WITH THE GFS/HIGH RES WRF
ARW/NMMB/NSSL WRF.  THE HIGH RES MODELS SHOW 1-2 INCHES WITH
LOCALLY HIGHER MAXIMA SO A SLIGHT RISK OF EXCESSIVE RAINFALL WAS
MAINTAINED.


PETERSEN
$$





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