Quantitative Precipitation Forecast
Issued by NWS

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745
FOUS30 KWBC 250839
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
438 AM EDT WED MAY 25 2016

...VALID 12Z WED MAY 25 2016 - 12Z THU MAY 26 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WSW ERV 35 SSE COT 40 SSW HBV 55 NNE MMAN 6R6 20 WSW SJT
20 WSW ERV.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
AUW ENW 10 SW IGQ 15 SSE C09 SFY 15 S FKA MGG 15 WSW CDD AUW.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNW UNO 25 ESE POF 15 NW HOP 20 SE CKV 45 SW BNA 35 W MSL
25 SE OLV AWM 25 NW AWM 10 SSE M19 15 SW LIT 35 ENE TXK
25 WSW TXK 25 NNE PRX 10 NE MLC 15 NNW TQH 30 SE JLN 25 NNW UNO.


...UPPER MIDWEST...

CONVECTION WILL BE WIDESPREAD...BUT FORCING MECHANISMS ARE A
LITTLE NEBULOUS...AND RAPID SWINGS IN THE HIGH RESOLUTION GUIDANCE
BETWEEN 12Z AND 00Z CYCLES INTRODUCE SOME DOUBT AS TO THE DETAILS.
OUR BEST ESTIMATION IS THAT POTENTIAL FOR FOCUSED HEAVY RAIN AND
SOME DURATION OF TRAINING ECHOES WILL BE GREATEST NEAR A REMNANT
OUTFLOW BOUNDARY / BAROCLINIC GRADIENT IN SOUTHERN WISCONSIN AND
SOUTHEAST MINNESOTA THIS AFTERNOON. WE ALSO KEPT THE RISK AREA
DOWN TOWARD NORTHERN ILLINOIS...ALTHOUGH THE NEW HI-RES RUNS ARE
QUITE A BIT DRIER THERE. WITH BROAD TROUGHING...EMBEDDED
SHORTWAVES...AND OUTFLOW BOUNDARIES ALL IN PLAY...THERE STILL
APPEARS TO BE SOME POTENTIAL FOR LOCAL TRAINING OF
CELLS...ESPECIALLY GIVEN PERSISTENT AND INCREASINGLY MOIST
SOUTHWESTERLY LOW LEVEL FLOW.


...EASTERN OKLAHOMA TO WESTERN TENNESSEE...

A PREFERRED STORM/MCS TRACK HAD BEEN ON THE NORTHERN AND EASTERN
PERIPHERY OF THIS WARM MID LEVEL CAP...AND EACH SUCCESSIVE DAY OF
CONVECTION HAD BEEN SHEDDING DEPRESSIONS IN THE HEIGHT FIELD
DOWNSTREAM INTO THE MID MISSISSIPPI VALLEY. SEE NO REASON FOR THIS
PATTERN TO BREAK TODAY. THE LEADING
DEPRESSION/TROUGH HAD PRODUCED HEAVY RAIN IN AR/MO TUESDAY...AND
THERE ARE SHORT TERM SIGNALS THAT CONVECTION MAY IGNITE AGAIN WITH
THIS FEATURE OVER WESTERN TENNESSEE AND ADJACENT STATES EARLY
WEDNESDAY...WITH CONVERGENT MID LEVEL FLOW AND LOW LEVEL UPGLIDE
INTO THE BACK SIDE OF THE TROUGH. MOISTURE AND INSTABILITY
CONTINUE TO EXPAND EASTWARD TODAY WITH THE SLOWLY MIGRATING UPPER
PATTERN...SUCH THAT CHANCES FOR RAIN SPREAD TOWARD THE
APPALACHIANS AND OHIO VALLEY...WHILE THE HEAVIER RAIN AND FLASH
FLOOD POTENTIAL SHOULD LAG A BIT...BACK ACROSS WESTERN TENNESSEE
AND BACK WESTWARD TO THE CAPPING INVERSION...BASICALLY EASTERN
OKLAHOMA. THE QPF WAS STITCHED TOGETHER USING OBSERVATIONAL
TRENDS...HRRR TRENDS...EARLY ON...AND TRANSITIONING TO A BLEND OF
THE 00Z GFS AND WRF-ARW...ALONG WITH EXTRAPOLATION / PATTERN
RECOGNITION IN AREAS WHERE THE MODELS WERE NOT SATISFACTORY. ONE
SUCH AREA WAS THE MULTI-STATE AREA CONNECTING KS/OK/AR/MO...AND
ALSO SOUTHEAST OK...WHERE MODELS WERE NOT PERFORMING WELL.


...SOUTHWEST TEXAS...

MAINTAINED AN INHERITED SLIGHT RISK HERE. RIGHT MOVING SUPERCELLS
WILL BE VERY SLOW...WITHIN A REGIME CHARACTERIZED BY STRONG
INSTABILITY AND HIGH MOISTURE CONTENT...HENCE POTENTIAL FOR HIGH
PRECIPITATION SUPERCELLS AND LOCALLY INTENSE RAIN RATES. COVERAGE
OF ANCHORED CELLS PRODUCING A FLASH FLOOD THREAT MAY BE
SPARSE...BUT OPTED TO KEEP CONTINUITY RATHER THAN DOWNGRADE TO SEE
TEXT/MARGINAL.


...KS/NE/IA/MO...

BROAD BAROCLINICITY HAS BEEN PERSISTENT ALONG THE NORTHERN FRINGES
OF THE CAPPED AIRMASS / ELEVATED MIXED LAYER EXTENDING OUT OF WEST
TEXAS INTO SOUTHWEST KANSAS. THUS...REPEATED CLUSTERS OF DIURNALLY
DRIVEN CONVECTION HAVE TENDED TO ROLL OUT ACROSS SOUTHERN
NE/NORTHERN KS AND INTO ADJACENT IA/MO IN RECENT DAYS. SIMILAR
ACTIVITY IS EXPECTED WEDNESDAY AND WEDNESDAY NIGHT. WE NOTE A
LOCAL MAXIMUM OF MOISTURE TRANSPORT IN THE GFS ACROSS THIS
REGION...BUT AT TIMES THOSE SYNOPTIC SIGNALS HAVE NOT BEEN AS
PREDICTIVE OF ORGANIZED HEAVY RAIN...OWING TO DISRUPTION VIA
CONVECTIVE CLUSTERS AND OUTFLOWS OCCURRING ELSEWHERE. WITHOUT MUCH
CONFIDENCE AS TO THE EXACT PLACEMENT OF CONVECTION IN
NE/KS/IA/MO...AND WHETHER SUCH CONVECTION WOULD OVERLAP WITH WET
ANTECEDENT CONDITIONS...WE STOPPED SHORT OF ADDING A SLIGHT RISK
OF EXCESSIVE RAINFALL HERE...BUT WILL GAVE TO MONITOR TRENDS FOR
POSSIBLE INTRODUCTION.

BURKE
$$





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