Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FOUS30 KWBC 281413
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1012 AM EDT TUE APR 28 2015

...VALID 15Z TUE APR 28 2015 - 12Z WED APR 29 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...



1400 UTC UPDATE

CENTRAL TO SOUTH FLORIDA

NO SIGNIFICANT CHANGES IN THINKING FROM THE PREVIOUS EXCESSIVE
RAINFALL POTENTIAL OUTLOOK.  HEAVIEST RAINS LIKELY TO REMAIN
OFFSHORE OF SOUTHWEST FLORIDA---AS PER LATEST SATELLITE
IMAGERY---AXIS OF HIGHEST MUCAPE..AND   STILL---HEAVY RAIN
POTENTIAL WILL PERSIST INLAND ALONG AND TO THE SOUTH OF THE
STATIONARY FRONTAL BOUNDARY CURRENTLY ACROSS THE CENTRAL PORTION
OF THE STATE IN THE AXIS OF MUCH ABOVE AVERAGE PW VALUES---2 TO
2.5+ STANDARD DEVIATION ABOVE THE MEAN AND MUCAPE VALUES 1500 TO
2000 ALONG AND SOUTH OF THIS FRONT.  HIGH FFG VALUES WILL BE THE
BIGGEST DETERRENT TO WIDESPREAD RUNOFF ISSUES.  HOWEVER---INTENSE
RAINFALL RATES WILL STILL LIKELY PRODUCE ISOLATED RUNOFF ISSUES IN
URBANIZED AREAS WHERE A QUICK 1-2" MAY OCCUR IN AN HOUR OR TWO.
CONVECTION LIKELY TO BUILD SOUTHWARD INTO SOUTH FLORIDA THIS
AFTERNOON--COMING TO AN END PRIOR TO 0000 UTC WHEN HIGHEST CAPE IS
SHUNTED SOUTHWARD BY ASSOCIATED OUTFLOW.

ORAVEC

ORAVEC

PREVIOUS DISCUSSION

...CENTRAL AND SOUTH FLORIDA...

THE AIRMASS WILL BECOME INCREASINGLY MOIST TODAY...WITH PW
APPROACHING 2-2.25 INCHES...AND ANOMALIES BASED ON THE
SREF/GEFS/ECMWF ENSEMBLES REACHING 3 STANDARD DEVIATIONS FROM
CLIMATOLOGY...OR ABOVE THE 95TH PERCENTILE FOR LATE APRIL. FLASH
FLOOD GUIDANCE VALUES ARE LARGE...PER USUAL...BUT THIS TYPE OF
AIRMASS WOULD OBVIOUSLY SUPPORT INTENSE HOURLY RATES...ESPECIALLY
GIVEN THE UNSEASONABLY ROBUST DYNAMICAL FORCING (SHORTWAVE ENERGY
COUPLED WITH RIGHT ENTRANCE REGION FORCING FROM THE UPPER LEVEL
CONFLUENCE ZONE ACROSS THE CAROLINAS AND SOUTHEAST). PER CONSENSUS
OF HIGH RES SIMULATED REFLECTIVITY LOOPS...THE GREATEST RISK OF
HEAVY (POTENTIALLY EXCESSIVE) RAINFALL WILL OCCUR DURING THE
AFTERNOON/EVENING (COINCIDING WITH THE BEST DEEP-LAYER ASCENT
ALONG AND NORTH OF THE SURFACE BOUNDARY). AT THE SAME TIME...GIVEN
THE ANTECEDENT WIDESPREAD CLOUD COVER AND SHOWERS/TSTM ACTIVITY
THIS MORNING...DO NOT EXPECT THE TYPICAL DIURNAL CONTRIBUTION TO
THE DEGREE OF DEEP-LAYER INSTABILITY...AS MUCAPES ARE EXPECTED TO
AVERAGE AOB 1000 J/KG THIS AFTERNOON/EVENING ACROSS THE NORTHERN
2/3 OF THE PENINSULA. WPC UTILIZED A GLOBAL MODEL CONSENSUS WITH
THE AXIS OF THE HEAVIER RAINFALL (00Z
GFS/ECMWF/GEM/UKMET)...THOUGH GIVEN THE VARIANCE WITH THE
AMOUNTS...AREAL AVERAGE QPF IS EXPECTED TO BE WITHIN THE 1-2 INCH
RANGE. NEVERTHELESS...ISOLATED HIGHER AMOUNTS IN THE 4-6+ INCH
RANGE ARE ANTICIPATED AS PER THE HIGH RES GUIDANCE...WHICH DESPITE
THE INITIALLY HIGH FFG...WOULD LEAD TO AT LEAST LOCALIZED RUNOFF
ISSUES IN THE SHORT TERM (WITHIN A 3-6 HOUR PERIOD).

HURLEY

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.