Quantitative Precipitation Forecast
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FOUS30 KWBC 150809
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
408 AM EDT SAT JUL 15 2017

...VALID 12Z SAT JUL 15 2017 - 12Z SUN JUL 16 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 S KGVX 20 ENE KRP VCT 10 W DWH 25 W IER 20 S LLQ 15 NNW AWM
25 WSW HOP 35 NNE CSV 10 SSW UKF 10 ENE NTU 90 ENE HSE
45 ESE MRH 25 S SUT 15 ENE NBC 35 WNW JYL 3J7 15 NNW FFC
55 W MGM 20 N HSA 15 WSW 2GL 10 W KSPR KVQT.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 SSW NYL 35 ENE IPL 20 ENE BLH 60 W LUF GYR 30 SSW PRC
30 NW PRC 15 N INW 55 ESE SJN 35 S ABQ 20 W ROW 15 SW PEQ
45 SSE E38 120 S E38 90 SSE MMCU.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 WNW 4SL 15 ENE CEZ 10 W GUC 15 NW BJC 35 S IML 15 NW GBD
20 NNW PNC 10 ENE TUL 15 WNW RKR 10 SW LBR 10 S GVT 15 ENE DTO
15 SSE PVJ OKC 30 SSE WWR 30 E CAO 50 SSE RTN 15 SSE SAF
35 WNW 4SL.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 WNW GSB 10 ENE EDE 25 E FFA 20 NE HSE 30 SE NCA 10 NW SUT
20 W MYR 10 NE FLO 10 WNW GSB.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NW TUP MDQ 10 S GAD 15 SSW TCL 30 NNE PIB 25 NNW MCB
30 SW GWO 25 NW TUP.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 NNW ITR 45 NNW DDC 45 NNW WWR 20 SE SPD 35 NNW TAD
20 NNW AFF 40 NNW ITR.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
75 SW MMCS 25 NNE DMN 60 NE TCS 15 SE SRR 35 SE GDP 10 S MRF
70 SW MRF 65 NNE MMCU.


...MID SOUTH / ALABAMA / MISSISSIPPI...

WE ARE STUCK IN A REPEATING PATTERN IN WHICH DIURNAL THUNDERSTORMS
FORM ALONG THE GULF COAST SEA BREEZE AND SEPARATELY ALONG A WAVY
FRONTAL BOUNDARY IN THE LOWER MS / TN VALLEY BEFORE MEETING IN THE
MIDDLE. USING MOISTURE IN THE 700-500 MB LAYER TO TRACE THE
GREATER COVERAGE OF CONVECTIVE RAINFALL POINTS US TOWARD A
SATURDAY FORECAST THAT FAVORS THE 00Z GFS AND NSSL WRF...WITH THE
18-21Z MAXIMUM IN LAYER RELATIVE HUMIDITY ORIENTED FROM SOUTHWEST
MISSISSIPPI TO NORTHERN
ALABAMA / FAR NORTHWEST GEORGIA. COLLISION OF OUTFLOWS WITHIN A
SEASONABLY MOIST AND UNSTABLE ENVIRONMENT WILL SUPPORT ISOLATED
HEAVY RAINFALL TOTALS AND A RISK OF FLASH FLOODING...ESPECIALLY
OVER PARTS OF MS/AL WHERE THE WPC MANUAL AREAL AVERAGE QPF IS
MAXIMIZED.


...CAROLINAS...

SIMILAR TO THE GULF COAST STATES...CONVECTION IS LIKELY TO FORM
BOTH ALONG SEA BREEZES AND IN THE ELEVATED TERRAIN FARTHER
INLAND...AND THEN MEET. THERE IS A BIT MORE WESTERLY MID LEVEL
FLOW AND STRONGER SOUTHWESTERLY LOW LEVEL INFLOW HERE...WHICH MAY
GIVE COLLIDING THE TRAINING THUNDERSTORMS MORE STAYING POWER /
LONGEVITY...ALLOWING FOR SOME EXCESSIVE LOCAL RAINFALL TOTALS.
MODELS SHOW A CONSISTENT HEAVY RAINFALL SIGNAL FROM MYRTLE BEACH
UP THROUGH THE OUTER BANKS...AND GENERALLY EAST OF I-95.


...SOUTHWEST U.S. / SOUTHWEST TEXAS...

THERE IS A MULTI-MODEL SIGNAL FOR HEAVY RAIN IN THE EL PASO AREA
PERHAPS AS EARLY AS THE MORNING HOURS. THE CIRA LAYER PW SATELLITE
PRODUCT FOR 700-500 MB SHOWS A SLUG OF MOISTURE MIGRATING INTO
THAT REGION ALONG THE CONVERGENT EASTERN PERIPHERY OF A BROAD
EASTERLY WAVE MIGRATING THROUGH NORTHERN MEXICO. ONCE
THUNDERSTORMS FORM THEY WILL EXPERIENCE SOME ENHANCED
SOUTHEASTERLY INFLOW AT 850-700 MB TO SUPPORT REGENERATION AND
SMALL SCALE TRAINING ALONG OUTFLOWS...RESULTING IN A RISK OF HEAVY
RAINFALL AND FLASH FLOODING. THE DISTRIBUTION OF MOISTURE WILL
ALSO CONTINUE TO FAVOR SOUTHERN
ARIZONA FOR RELATIVELY ORGANIZED CONVECTION AND RISK OF FLASH
FLOODING ASSOCIATED MORE WITH THE SHORT TERM RAIN RATE AND QUICK
RESPONDING TERRAIN. WIND PROFILES ARE MORE FAVORABLE FOR TRAINING
AND PERHAPS MORE EXCEPTIONAL EVENT TOTAL RAINFALL AMOUNTS OVER
SOUTHERN NEW MEXICO AND SOUTHWEST TEXAS.


...COLORADO / KANSAS / NEW MEXICO / OKLAHOMA...

NOCTURNAL VEERING OF LOW LEVEL WINDS...THEN INDUCING WEAK WARM
ADVECTION...COULD LEAD TO INITIATION OF ELEVATED THUNDERSTORMS
OVER EASTERN OKLAHOMA THIS MORNING. IF THIS OCCURS STORMS WILL BE
SLOW MOVING AND A CAPABLE OF HEAVY RAIN...ALTHOUGH THE WIND SPEEDS
/ FORCING WILL BE VERY WEAK AND THE HRRR WAS TENDING TO KEEP THE
AREA DRY.

OF MORE CONCERN IS EASTERN COLORADO AND WESTERN KANSAS. WE WILL
HAVE TO WATCH THIS AREA DILIGENTLY FOR HEAVY RAINFALL. THERE ARE
SEVERAL FAVORABLE INGREDIENTS IN PLACE WITH AMPLE SUMMERTIME
MOISTURE COINCIDENT BENEATH A PERSISTENT UPPER LOW / SHEAR AXIS.
THE DEEP LAYER WIND SPEEDS...HOWEVER...WERE SO WEAK THAT THE
DIURNAL THUNDERSTORM ACTIVITY IN RECENT DAYS HAD TENDED TO BE VERY
SMALL SCALE AND NOT SUPPORTED MUCH AFTER DARK. ALL IT WOULD TAKE
IS A TIMELY ARRIVAL OF GREATER UPPER DIVERGENCE TO ENHANCE THIS
SMALL WEATHER SYSTEM AND ITS RAINFALL PRODUCTION. ALTHOUGH SUCH AN
OCCURRENCE IS NOT EXPECTED ON THE SYNOPTIC SCALE...THE HI-RES
MODELS ARE EVEN MORE EMPHATIC IN PRODUCING ORGANIZED HEAVY RAIN
OVER THE REGION SATURDAY AND SATURDAY EVENING. THE MODELS HAVE
BEEN STRUGGLING...OVER-FORECASTING THE QPF PROBABLY BECAUSE OF THE
SMALL SCALE OF THE INDIVIDUAL THUNDERSTORMS. WPC QPF MAY STILL BE
A LITTLE ON THE HEAVY SIDE OVERALL...BUT THERE IS POTENTIAL FOR
LOCALLY VERY HEAVY RAINFALL WHEREVER THE MORE PERSISTENT CELLS ARE
ABLE TO FORM...WITHIN SOUTHERN/EASTERN CO AND WESTERN KS. MARGINAL
RISK EXTENDS AROUND THE SOUTHERN PERIPHERY OF THE UPPER LOW...INTO
NEW MEXICO WHERE HEAVY SHORT TERM RAINFALL IS POSSIBLE...THOUGH
WIND PROFILES WILL BE LESS FAVORABLE FOR TRAINING HERE COMPARED TO
AREAS EAST OF THE COLORADO FRONT RANGE.


...SOUTHEAST TEXAS / LOUISIANA...

ALTHOUGH THE FRONTAL BOUNDARY IN THE SOUTHERN PLAINS WILL MOVE
VERY LITTLE...NORTHERLY DEEP LAYER FLOW IS EXPECTED TO INCREASE IN
STRENGTH AS AN INVERTED TROUGH / EASTERLY WAVE CONTINUES TO
MIGRATE WESTWARD ALONG THE GULF COAST. THIS SHOULD PROMOTE
THUNDERSTORMS PROGRESSING SOUTHWARD AND PRODUCING ANOTHER RELATIVE
MAXIMUM SWATH OF RAINFALL OVER EAST TX AND WESTERN LA. AS IN OTHER
PARTS OF THE SOUTH...SOME COLLISIONS OR FOCUS ALONG THE SEA BREEZE
COULD LEAD TO HEAVIER LOCAL TOTALS...ESPECIALLY THE UPPER TX COAST
AND SOUTHWEST LOUISIANA.

BURKE
$$





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