Quantitative Precipitation Forecast
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FOUS30 KWBC 050048
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
848 PM EDT TUE AUG 04 2015

...VALID 01Z WED AUG 05 2015 - 12Z WED AUG 05 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NW HLC 30 NW HLC 20 SSE MCK 10 WNW MCK 25 NNW MCK 30 N MCK
20 SSE LBF 20 SE LBF 25 ESE LBF 10 NNW LXN 20 ENE LXN EAR
15 W HSI HSI 20 ESE HSI 20 N HJH 25 NNE HJH 20 NW BIE 20 SSW OFF
15 W RDK 20 E RDK 10 SE CSQ 35 NNW IRK 25 WNW UIN 30 SW PPQ
30 NNE VIH 20 WNW VIH 10 SSE AIZ 15 NNW SGF 25 W SGF 10 SE JLN
20 NW GMJ 20 SSW BVO 20 WSW WLD 10 N HYS 20 NW HLC.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 S JDN 20 E JDN 35 S OLF 10 NE GDV 30 SE BHK 40 SSE 2WX
25 E RCA 30 SE RAP 30 NW IEN 35 NNW CDR 30 SSW CUT 35 SW CUT
50 WSW CUT 20 N GCC 55 S JDN.


0100 UTC UPDATE

CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WERE
TO RELATIVELY MINOR...TRIMMING NRN PORTIONS OF SLIGHT RISK AREA
ACRS THE CNTL PLAINS/MID MS VALLEY WHERE HEAVY RAINFALL THREAT
CONTINUES TO DIMINISH.  OTHERWISE...STILL SEE POTNL OVERNIGHT FOR
HEAVY TO PSBL EXCESSIVE RAINS DVLPG AHEAD OF CNVTVLY ENHANCED VORT
DROPPING ESEWD OUT OF SRN NEB/NRN KS.  WITH SLIGHT INCREASE IN LOW
LEVEL JET/WAA INTO E/W FRONTAL BNDRY DRAPED ACRS THE REGION.

 SLIGHT RISK AREA ACRS ERN MT INTO NE WY/WRN SD STILL HAS SOME
RESIDUAL AFTERNOON INSTABILITY TO FEED OFF HEAD OF WEAK SHEER AXIS
PROGRESSING EWD FROM THE NRN HI PLAINS.  SFC DATA SHOWS FAVORABLE
BUT WEAK CONVERGENCE ACRS ERN WY INTO WRN SD AS OF 00Z..WHICH
SHOULD SUPPORT ACTIVITY ACRS THIS AREA FOR A FEW MORE HRS BEFORE
STRENGTHENING LOW LEVEL JET SHIFTS BETTER WAA LIFT NWD INTO WRN
ND..BUT WITH A GENL DECREASE IN HEAVIER PCPN POTNL.

ACRS THE NC COAST...WHILE CONVECTION HAS BEEN FAIRLY MINIMAL
THROUGH EARLY EVENING...WEAK CIRCULATION CONTINUES TO DRIFT NEWD
NEAR THE SRN NC COAST WITH WEAK CONVERGENCE ALONG THE IMMEDIATE
COASTAL AREA AHEAD OF THE LOW WHICH COULD STILL FAVOR SOME TSTM
DVLPMENT OVERNIGHT.  AT THIS TIME BELIEVE HEAVIER RAINS WILL STAY
OFFSHORE..BUT CAN NOT RULE OUT SOME ISOLD HEAVIER RAIN BANDS
SETTING UP ACRS ERN NC.


ELSEWHERE---NO CHANGES MADE TO THE OTHER AREAS OF CONCERN OVER THE
NORTHERN PLAINS.

SULLIVAN

PREVIOUS DISCUSSION

...NORTHERN ROCKIES/CENTRAL PLAINS/MID MS VALLEY...

MOISTURE AND INSTABILITY NORTH OF A STATIONARY FRONT STRETCHING
FROM THE NORTHERN ROCKIES THROUGH THE CENTRAL PLAINS INTO THE MID
MS VALLEY WILL FUEL CONVECTION THAT COULD PRODUCE HEAVY TO
EXCESSIVE RAINFALL DURING DAY 1.

IN THE NEAR TERM...THE THREAT FOR FLASH FLOODING IS FOCUSED NORTH
OF A STATIONARY FRONT EXTENDING FROM THE NORTHERN ROCKIES INTO THE
MID MS VALLEY.  STRONG INSTABILITY AND PRECIPITABLE WATER VALUES
NEAR 1.30 INCHES ON THE NOSE OF A LOW LEVEL SOUTHEAST INFLOW WILL
FEED CLUSTERS OF CONVECTION ALONG THE LENGTH OF THE AXIS...WHICH
COULD PRODUCE LOCAL 2+ INCH RAINFALL AMOUNTS. THE BEST INSTABILITY
SHOULD BE EXHAUSTED BY 04/12Z ACROSS PORTIONS OF THE NORTHERN
ROCKIES AND CENTRAL PLAINS...BUT COULD BE ONGOING ACROSS THE MD MS
VALLEY THROUGH THAT TIME.

ACROSS MT/SD/NE...THE MOIST INFLOW CONTINUES THROUGH THE MID TO
LATE AFTERNOON...AND MODEL SOUNDINGS SHOWED STRONG INSTABILITY AND
PRECIPITABLE WATER VALUES NEAR 1.50 INCHES DURING THIS TIME
PERIOD. CLUSTERS OF CONVECTION NORTH OF THE FRONT COULD SLOW OR
EVEN BACKBUILD ACROSS SD/NE AS DOWNWIND CORFIDI VECTORS DROP BELOW
10 KNOTS. LOCAL 1.00 INCH QPF AMOUNTS WERE PLACED ALONG THE FRONT
FROM WESTERN SD THROUGH SOUTH CENTRAL NE...BUT LOCALLY HIGHER
AMOUNTS ARE POSSIBLE GIVEN THE INSTABILITY AND MOISTURE PROFILES.
SOME HIGH RESOLUTION GUIDANCE (SUCH AS THE 00Z WRF
ARW/NMMB AND 00Z NAM CONEST) SUGGEST 2.00 INCH AMOUNTS ARE
POSSIBLE...ESPECIALLY FROM SOUTHEAST MT ACROSS WESTERN SD. GIVEN
THE MOISTURE AND INSTABILITY IN PLACE...AND THE POTENTIAL FOR
HIGHER QPF AMOUNTS PER THE HIGH RESOLUTION GUIDANCE...A SLIGHT
RISK AREA WAS PLACED OVER PORTIONS OF SOUTHEAST MT INTO NORTHEAST
WY AND WESTERN SD.

FURTHER SOUTHEAST...ONGOING CONVECTION ACROSS NORTHERN MOS AND
EASTERN NE SHOULD START TO WEAKENING TOWARD 04/12Z...AS THE
REMAINING MUCAPE IS EXHAUSTED. THE ACTIVITY COULD PERSIST PAST
THIS POINT...BUT THE MAIN FLASH FLOOD THREAT SHOULD BE CONFINED TO
12Z OR SO. HIGH RESOLUTION GUIDANCE...SUCH AS THE 00Z WRF
ARW/NMMB...SUGGEST THAT THE THREAT COULD LAST A BIT LONGER...BUT
HIS WILL BE COVERED BY A SLIGHT RISK FOR LATER ACTIVITY.

OTHERWISE..THERE IS A MULTI MODEL SIGNAL FOR AN MCS TO DEVELOP
ACROSS EASTERN KS INTO WESTERN MO DURING THE SECOND HALF OF THE
PERIOD. THE LATEST WRF SIMULATED SATELLITE IMAGERY SUGGESTS THE
DEVELOPMENT OCCURS OVER EASTERN KS AFTER 05/03Z AND PEAKS NEAR
05/06Z OVER WEST CENTRAL MO...AS STRONG LOW LEVEL MOISTURE FLUX IS
TRANSPORTED ION THE NOSE OF A LOW LEVEL JET ACROSS EASTERN KS. THE
00Z NAM IS ALONE WITH A MORE NORTHERLY DEVELOPMENT OF THE MCS
ACROSS NE...WHILE THE REMAINDER OF THE 00Z REGIONAL/GLOBAL
GUIDANCE...AS WELL AS MOST OF THE HIGH RESOLUTION
GUIDANCE...POINTS TOWARD KS/MO. AN AREA OF 1.25 TO 1.50 INCHES OF
QPF WAS PLACED OVER THIS REGION...BUT LOCAL 3.00 INCHES AMOUNTS
ARE POSSIBLE GIVEN THE POTENTIAL FOR HIGH RAINFALL RATES. A SLIGHT
RISK AREA WILL BE RETAINED OVER PORTIONS OF KS/MO FOR THE FLASH
FLOOD THREAT.


...MID ATLANTIC...

DEEP MOISTURE STREAMING ALONG A SURFACE BOUNDARY BECOMES FOCUSED
BY THE PASSAGE OF A SURFACE WAVE ON THE FRONT...RESULTING IN THE
DEVELOPMENT OF CONVECTION WITH HEAVY TO POSSIBLY EXCESSIVE
RAINFALL NEAR THE NC/SC COAST.

CONVECTION ALONG THE NC/SC COASTS HAS INCREASED IN INTENSITY EARLY
THIS MORNING...IN RESPONSE TO BETTER LOW LEVEL CONVERGENCE ALONG
THE SC COAST AND PRECIPITABLE WATER VALUES NEARING 2.25 INCHES.
THE LOW LEVEL SOUTHEAST INFLOW TRANSPORTS INSTABILITY ONSHORE
ACROSS THE REGION THIS MORNING...AND HIGH RESOLUTION GUIDANCE
SUGGESTS THAT LOCAL 2 TO 3 INCH AMOUNTS ARE POSSIBLE THROUGH
04/12Z. THIS AREA WILL NEED TO BE COVERED BY  SEE TEXT...MAINLY
FOR THIS MORNING...TO ACCOUNT FOR THE CONVECTION IN THE DEEP
TROPICAL AIRMASS.

HAYES
$$





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