Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 290803
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
402 AM EDT MON AUG 29 2016

...VALID 12Z MON AUG 29 2016 - 12Z TUE AUG 30 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
85 WSW SPG 50 WSW PIE 15 SSW BKV 15 ESE BOW 10 E MCO 30 SSE AYS
15 SSE TBR 15 S CTZ MQI 100 E HSE.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 ESE BRO 35 ESE BRO 10 S PIL 30 SE BKS 15 S SSF 15 NE 6R9
15 SSE INJ 10 ESE OCH POE 20 NNW GAO 15 SSW KMIS 20 NNW CYD.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 NNE ERY 25 ENE MTW 20 S CMY 10 W 1G2 15 SW DXX 10 ESE ETH
25 NNW AXN XVG 25 NE BFW 35 SSE CWEC.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
140 SE DUG 105 SW MMCS 55 WSW MMCS 25 NNW LRU 55 S ABQ
15 SSE ALS 30 ENE CCU DEN 30 ESE LIC 20 WNW MCK 25 NNW EAR
15 WSW SLB 15 E OLZ 20 NE VYS 10 SSE FFL OJC 15 ESE JWG
15 SE MDD 20 NE 6R6 45 S 6R6.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WNW OKV 15 SSE LWB 10 ENE BKW 10 E W22 20 WNW OKV.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 S APF 15 SSW FMY 10 ESE RSW 40 ESE APF 35 WNW FXE 20 WSW PBI
SUA 15 E SUA 30 ENE PBI.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 N KOPM 30 W KMIU 10 N CRP 50 W VCT 15 W 62H 20 WSW UTS
10 ESE UTS DRI 25 W LFT 15 S KVNP.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 NE IWD 30 N IMT 25 NNE MNM 10 S CLI 30 NNE ONA 10 SSW GHW
10 SW AIT 20 E DYT 40 S GNA 20 WNW IWD 35 NE IWD.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 ESE MMCS 25 W HMN 30 WNW 4CR 25 N CQC 15 W RTN 30 NNE VTP
35 WSW APA 20 SW APA COS 10 NE PUB 30 SE TAD 60 WSW CAO
60 ENE 4CR 20 ENE TCC 30 S DHT 30 SSE SPD 20 ESE LBL 15 SW GAG
35 E PVW 25 SSE LBB 25 SW FST 15 WNW 6R6 75 SSE E38 95 S E38
70 SSW GDP 25 ESE MMCS.



MN/WI/MI
~~~~~~~~
A MESOSCALE CONVECTIVE SYSTEM (MCS) ACROSS NORTHERN MN AT THIS
TIME IS EXPECTED TO MOVE EAST-SOUTHEAST ALONG A GRADIENT OF THE
MUCAPE FIELD INTO NORTHERN WI INTO THE MORNING HOURS BEFORE
DISSIPATING AROUND NOON.  STAYED CLOSEST TO THE 12Z ARW, 00Z NSSL
WRF, AND 00Z NAM SOLUTIONS HERE.  ADDITIONAL STORMS ARE LIKELY TO
FIRE ALONG THE SLOW MOVING TRAILING COLD FRONT, POTENTIALLY GOING
OVER LOCATIONS WHERE HEAVY RAIN FROM THE MCS WILL FALL OVER THE
NEXT FEW HOURS.  THE MESOSCALE GUIDANCE INDICATES LOCAL AMOUNTS IN
THE 2-4" RANGE BEING POSSIBLE, WHICH LOOKS PLAUSIBLE IN LOCATIONS
THAT GET MULTIPLE ROUNDS OF RAIN OR FALL VICTIM TO MESOSCALE WAVES
WITHIN THE EVOLVING QUASI-LINEAR CONVECTIVE SYSTEM.  A SLIGHT RISK
OF EXCESSIVE RAINFALL WAS ADDED FOR PORTIONS OF CENTRAL MN AND
NORTHERN WI BASED ON THIS QPF SOLUTION.


CENTRAL AND SOUTHERN PLAINS/FRONT RANGE OF THE ROCKIES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A WEAKENING NE/SW ORIENTED SHEAR AXIS ALOFT INTERACTING WITH
MOIST/UNSTABLE CONDITIONS EXTENDING FROM THE SOUTHERN HIGH PLAINS
THROUGH THE CENTRAL PLAINS INTO IA WILL LEAD TO WIDESPREAD MAINLY
DIURNAL TSTM ACTIVITY BUT WITH WEAK LOW LEVEL FLOW AND LACK OF STG
LOW LEVEL FOCUS, ACTIVITY ACRS THIS REGION WILL BE HIGHLY
MESOSCALE DRIVEN/POTENTIALLY PULSE.  ANOTHER ACTIVE THUNDERSTORM
DAY IS EXPECTED FROM WESTERN TX AND EASTERN NM INTO KS, WITH SLOW
MOVING CELLS LEADING TO LOCALIZED HEAVIER RAINS, ON THE ORDER OF
2.5" AN HOUR.  THE MESOSCALE GUIDANCE SHOWS LOCAL MAXIMA IN THE
3-5" RANGE WITHIN THIS REGION.  BECAUSE OF LOW FLASH FLOOD
GUIDANCE VALUES CAUSED BY RECENT RAINS, A FAIRLY LARGE SLIGHT RISK
OF EXCESSIVE RAINFALL WAS ADDED FROM WESTERN TX, EASTERN NM, AND
THE FRONT RANGE OF THE CO ROCKIES.


WESTERN GULF COAST
~~~~~~~~~~~~~~~~~~
A WEAK UPPER LOW OVER THE NW GULF ALONG WITH A WEAK SFC REFLECTION
IS EXPECTED TO WEAKEN SLOWLY AND EXPECTED TO DRIFT SLOWLY TOWARD
THE WEST OR SOUTHWEST. AGREE WITH THE MODEL CONSENSUS IN KEEPING
HEAVIER RAINS NEAR AND OFF THE TX/LA COASTS WITH BETTER LOW LEVEL
CONVERGENCE...BUT POCKETS OF HEAVIER DIURNAL TSTMS RAINS WILL
CONTINUE TO DVLP NWD INTO ERN TX/LA WITH DIFFERENTIAL HEATING
WITHIN UNSEASONABLY MOIST AIRMASS.  USED THE NORTHWARD PENETRATION
TO THE ECHOES SEEN ON RADAR THE PAST COUPLE DAYS TO HELP DEPICT
THE NORTHERN EXTENT, WHICH WAS A REASONABLE MATCH TO THE 12Z
ECMWF.  HOURLY RAIN RATES UP TO 3" ARE POSSIBLE WHERE CELLS MERGE
AND/OR TRAIN.  LOCAL AMOUNTS IN THE 3-5" RANGE ARE POSSIBLE PER
THE MESOSCALE GUIDANCE, AND SOME OF THIS REGION RECEIVED LOCALLY
HEAVY RAINFALL OVER THE PAST COUPLE DAYS WHICH HAS LOWERED FLASH
FLOOD GUIDANCE VALUES/SATURATED SOILS.  A SLIGHT RISK OF EXCESSIVE
RAINFALL WAS ADDED FOR WATER LOGGED SOUTHWEST LA AS WELL AS THE
MIDDLE AND UPPER TX COASTS.


FLORIDA
~~~~~~~
INCREASINGLY CONVERGENT LOW-LEVEL FLOW TO THE EAST OF TROPICAL
DEPRESSION #9 TRACKING THROUGH THE FLORIDA STRAITS/NEAR THE CUBAN
COAST WILL DRAW MOIST TROPICAL AIR WITH PRECIPITABLE WATER VALUES
OVER 2.25 INCHES INTO SOUTHERN FL WHICH SHOULD LEAD TO EFFICIENT
RAIN PRODUCING SHOWERS/THUNDERSTORMS, TO THE TUNE OF 3" AN HOUR
WHERE CELLS MERGE AND/OR TRAIN.  THESE SORT OF RAIN RATES WOULD
QUICKLY OVERWHELM THE URBANIZED KEYS AS WELL AS TOWNS/CITIES ALONG
THE SOUTHWEST AND SOUTHEAST FL COASTLINE.  LOCAL AMOUNTS IN THE
5-7" RANGE ARE EXPECTED OVER THE NEXT FEW DAYS.  SEE TROPICAL
CYCLONE ADVISORIES FROM THE NATIONAL HURRICANE CENTER FOR FULL
DESCRIPTION OF THE DEPRESSION AND ITS FORECAST TRACK AND STRENGTH.


EASTERN WV
~~~~~~~~~~
SCATTERED THUNDERSTORMS CAUSED BY DAYTIME HEATING WITHIN A MOIST
AIRMASS ARE EXPECTED OVER AN AREA WITH LOW FLASH FLOOD GUIDANCE
VALUES ACROSS PORTIONS OF EASTERN WV.  THOUGHT IT PRUDENT TO PLACE
A MARGINAL RISK IN THIS REGION.  LOCAL AMOUNTS IN THE 2-4" RANGE
ARE POSSIBLE HERE.


COASTAL CAROLINAS/GA
~~~~~~~~~~~~~~~~~~~~
WITH THE APPROACH OF TROPICAL DEPRESSION #8, EXPECT AN INCREASE IN
RAINS TOWARD THE OUTER BANKS OF NC.  OVER THE NEXT COUPLE OF DAYS,
HOURLY RAIN RATES UP TO 2.5" WHERE CELLS MERGE/TRAIN AND LOCAL
AMOUNTS IN THE 3-5" RANGE ARE POSSIBLE.  HOWEVER, IMPACTED AREAS
ACROSS EASTERN NC ARE PREDOMINANTLY SWAMPY, SO WENT WITH A
MARGINAL RISK OF EXCESSIVE RAINFALL RATHER THAN A SLIGHT RISK,
WHICH MAINTAINS GOOD CONTINUITY.  SEE TROPICAL CYCLONE ADVISORIES
FROM THE NATIONAL HURRICANE CENTER FOR FULL DESCRIPTION OF THE
DEPRESSION AND ITS FORECAST TRACK AND STRENGTH. OTHERWISE...AN
AXIS OF HIGHER MOISTURE ALONG WITH DECAYING FRONTAL BNDRY IN
BROADLY CYCLONIC FLOW WILL MAINTAIN A RISK OF THUNDERSTORMS ACROSS
THE COASTAL CAROLINAS.

ROTH
$$




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