Quantitative Precipitation Forecast
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FOUS30 KWBC 050658
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 AM EDT TUE MAY 05 2015

...VALID 06Z TUE MAY 05 2015 - 12Z WED MAY 06 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNE AQR 10 E GYI NFW 20 SSE 7F9 25 NNE JCT 60 NNE 6R6
25 ESE PEQ 10 SSW CNM 35 NE ROW 55 ENE 4CR CQC 15 NE SAF
35 SSE ALS 35 S PUB 55 W GCK 15 WSW DDC 25 NW AVK 25 NNW JWG
20 SSE END 30 ESE PNC 20 SSW BVO 10 NE OKM 20 NNE AQR.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
60 N DYS 10 NNW DYS 40 NNW SJT 20 SE MAF 25 NE INK 25 SSE HOB
40 WSW LBB 20 ESE PVW 45 SW CDS 35 S CDS 50 SW F05 60 N DYS.


...SOUTHERN HIGH PLAINS FROM ERN CO/NM OUT TOWARD I-35 IN OK AND
NORTH TX...

A PRONOUNCED THREAT OF ADDITIONAL FLASH FLOODING WILL CONTINUE
THROUGH AT LEAST 12Z AND POSSIBLY BEYOND...IN A FOCUSED AREA OF
WEST TEXAS AND FAR SE NM TO THE NORTH OF MIDLAND. THIS IS WHERE AN
OUTFLOW BOUNDARY HAD SET UP ORTHOGONAL TO A LOW LEVEL JET OF AT
LEAST 35 TO 45 KNOTS. CELLS WERE RELUCTANT TO PROPAGATE DOWNSTREAM
AS THE INSTABILITY AXIS WAS QUITE NARROW...BUT A VERY PERSISTENT
UPPER DIFLUENCE PATTERN AND DEEP LAYER LIFT WILL SUPPORT
REGENERATION OF CELLS ON THE WESTERN FLANK THROUGH THE EARLY
MORNING HOURS. IT APPEARS THE EVENT...WHICH HAD PRODUCED LOCAL 5
TO 7 INCH RAINFALL TOTALS...WILL ONLY BE SLOWED BY THE INEVITABLE
LESSENING OF INSTABILITY TOWARD DIURNAL MINIMUM...TENDING TO BRING
DOWN RAIN RATES. THE FEATURES SUPPORTING CELL
REGENERATION...HOWEVER...ARE FORECAST TO CONTINUE RIGHT ON INTO
THE DAYTIME WHILE MIGRATING SLOWLY EASTWARD...WHICH IS WHY WE
CARRIED A MODERATE RISK OF FLASH FLOODING NEAR AND SLIGHTLY EAST
OF THE ACTIVITY THAT WAS ONGOING AT 06Z.

UPSLOPE INTO THE HIGHLANDS OF NORTHEAST NM WILL ALSO PERSIST EARLY
IN THE PERIOD. SOME VERY SMALL SCALE HEAVY RAINFALL HAD BEEN
ESTIMATED BY RADAR IN THE VICINITY OF SANTA ROSA. WE MAINTAINED A
WESTWARD EXTENSION OF THE SLIGHT RISK AREA TO CONTAIN THIS
ACTIVITY...BUT ANTICIPATE A SLACKENING OF LOW LEVEL UPSLOPE AS THE
AXIS OF MID/UPPER LEVEL FORCING LIFTS TO THE NORTH AND EAST.

ELSEWHERE...WE MAINTAINED A BROAD SLIGHT RISK AREA IN PARTS OF
CO/KS/OK/TX/NM TO ENCOMPASS SUSTAINED SOUTHERLY LOW LEVEL FLOW AND
LARGE SCALE UPPER LEVEL FORCING WHICH SLIDES THROUGH THE SOUTHERN
PLAINS IN THE NEXT 24-30 HOURS. WHILE THIS KEEPS CONTINUITY FROM
PREVIOUS FORECASTS AND COVERS THE MODEL CONSENSUS FOR MODERATE TO
HEAVY PRECIPITATION...CONFIDENCE IN ANY SPECIFIC FLASH FLOOD EVENT
IS LOWER THAT IT WAS FOR THE WEST TEXAS EVENT. HEIGHT FALLS WILL
BE MAXIMIZED FARTHER NORTH TOWARD KS/NE...BUT GREATER MOISTURE
DEPTH IS EXPECTED ALONG THE TAIL END OF THOSE HEIGHT
FALLS...SUPPORTING A HEAVY RAIN ENVIRONMENT OVER PRIMARILY OK/TX
DURING THE AFTERNOON AND TUESDAY NIGHT. THE QPF DETAILS APPEARED
BETTER HANDLED BY THE 00Z WRF-ARW AND GEM REGIONAL...AS WELL AS
THE GFS AND 12Z ECMWF. THE MODEL SIGNAL IS NOT PARTICULARLY
HEAVY...BUT WITH STRONGLY MERIDIONAL FLOW AND PW VALUES RISING TO
AROUND 1.5 INCHES WITHIN A PLUME EXTENDING NORTHWARD FROM THE SE
TX COAST...THERE IS POTENTIAL FOR TRAINING CELLS TO PRODUCE MORE
THAN 2 INCHES IN AN HOUR LOCALLY. THE FLASH FLOOD GUIDANCE VALUES
OF ROUGHLY 2.0 TO 2.5 INCHES IN 1 HOUR OR 2.50 - 3.0 INCHES IN 3
HOURS COULD BE EXCEEDED...ESPECIALLY OVER THE FAR EASTERN TX/OK
PANHANDLES INTO WRN OK...AND DEVELOPING FROM NORTH TX INTO
SOUTHERN AND CENTRAL OK WHERE A READY SUPPLY OF RICH MOISTURE AND
MODERATE INSTABILITY MAY BE MORE SUSTAINABLE.


...CENTRAL HIGH PLAINS INCLUDING CO/KS/NE/SD...

PASSAGE OF A MID LEVEL TROUGH EARLY IN THE DAY WILL END THE
UPSLOPE REGIME IN COLORADO...WHILE FOCUSING MOISTURE TRANSPORT
INTO NORTHWEST KS AND SW NE ALONG AN ADVANCING WARM FRONT. FARTHER
NORTH...UPSLOPE WILL DEVELOP INTO THE BLACK HILLS. PW VALUES DO
BECOME ANOMALOUSLY HIGH AT THIS LONGITUDE AS THE 0.75 INCH VALUES
COME CLOSE TO RAPID CITY BY TUESDAY EVENING. THIS WOULD BE OF
GREATER CONCERN EXCEPT THAT THE MODEL QPFS ARE QUITE TAME FOR
NOW...LIKELY OWING TO WEAK INSTABILITY. STILL...A HEAVY RAIN
THREAT COULD DEVELOP LOCALLY ANYWHERE FROM NW KS TO SW SD. WILL
WATCH THE MODEL CAPE AND QPF TRENDS FOR A STRONGER SIGNAL...AND
POSSIBLE INTRODUCTION OF A SLIGHT RISK OF EXCESSIVE RAINFALL OVER
THIS REGION.

BURKE
$$




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