Quantitative Precipitation Forecast
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FOUS30 KWBC 250022
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
821 PM EDT TUE MAY 24 2016

...VALID 01Z WED MAY 25 2016 - 12Z WED MAY 25 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 W HYS 15 WNW HLC 50 ENE HLC 20 NNW CNK 35 SSW BIE 20 NNE MHK
25 WNW FOE 10 ENE PPF 10 WSW GMJ FYV 15 NNW RUE 15 ENE M19
25 NNW AWM 20 SE UTA 20 N GLH 15 SSE LLQ 35 WNW ELD 30 WNW TXK
30 NNW PRX ADH 10 NE PWA 25 ESE AVK 15 NW P28 30 WSW GBD
35 W HYS.


0100 UTC UPDATE...THE PERSISTENCE OF CLUSTERS OF STORMS IN EASTERN
OK AND AR COMBINED WITH LIFT GENERATED ALONG ALONG OUTFLOW
BOUNDARIES SUGGEST SEVERAL MORE HOURS OF SHOWERS AND STORMS ARE
EXPECTED IN EASTERN OK AND CENTRAL/SOUTHERN AR.
INCREASES IN RAINFALL FROM THE ECMWF AND SEVERAL HIGH RESOLUTION
FORECASTS LIKE THE WRF ARW AND `SPC` WRF IN SOUTHEAST OK /ADJACENT
AR TONIGHT WARRANTS AN UPGRADE TO A SLIGHT RISK OF EXCESSIVE
RAINFALL.

THE THERMODYNAMICAL PROFILE (DEGREE OF DEEP-LAYER INSTABILITY
ALONG WITH PW VALUES CLIMBING BETWEEN 1.5-1.75") IS SUCH THAT
HEAVY TO POTENTIALLY EXCESSIVE RAINFALL WILL BE POSSIBLE INTO THE
SOUTHERN PLAINS-LOWER MS VALLEY THIS EVENING WHEN THE
STRENGTHENING LOW-LEVEL INFLOW AND DEEP-LAYER BULK SHEAR WOULD
SUPPORT MORE ORGANIZED ACTIVITY WITH AN INCREASED POTENTIAL.

THE AREA WAS NOT EXTENDED MUCH INTO WESTERN TN AS THE MID LEVEL
LAPSE RATES BECOME MORE STABLE...SO THE WEAKER 5-6 DEG C/KM LAPSE
RATES IN TN SHOULD LEAD TO WEAKENING INTENSITY OVER THE NEXT FEW
HOURS.

PETERSEN/HURLEY

PREVIOUS DISCUSSION BELOW...


...CENTRAL PLAINS AND MISSOURI VALLEY INCLUDING
CO/NE/KS/IA/MO/AR...

THERE IS GOOD OBSERVATIONAL EVIDENCE AND MODEL SIGNAL FOR
CONVECTION IN NORTHERN KANSAS TO EVOLVE EAST AND SOUTHEASTWARD
EARLY TODAY. FARTHER DOWNSTREAM...AN AREA OF CONCERN...NOT LIKELY
TO BE MODELED VERY WELL...IS THE DEPRESSION IN THE HEIGHT FIELD
LEFT BY PREVIOUS CONVECTION...WHICH WAS DRIFTING INTO MO/AR THIS
MORNING...AND WHICH MAY WELL YIELD FOCUSED CONVECTION TODAY AS THE
LOW LEVEL JET VEERS AND PRODUCES STRONG UPGLIDE INTO UNCAPPED
AREAS FROM FAR EASTERN OK EASTWARD AS INDICATED BY THE NAM CONEST
AND SOME HRRR RUNS. ALL OF THIS OCCURS ALONG THE CAPE GRADIENT AT
THE NORTHEASTERN PERIPHERY OF THE GREAT PLAINS CAP / ELEVATED
MIXED LAYER WITH 700 MB TEMPERATURES 9 TO 12 C. THOUGH LOWEST
LEVEL INFLOW IS FOCUSED BACK TO THE WEST...ELEVATED INFLOW FROM
THE CAPPED AND UNSTABLE SOURCE REGION MAY SUPPORT POCKETS OF HEAVY
RAINFALL ANYWHERE WITHIN THE SLIGHT RISK AREA...BUT ESPECIALLY
THIS MORNING FROM EASTERN KS INTO MO/AR...AND TUESDAY NIGHT FROM
SOUTHERN NE INTO ADJACENT KS/IA/MO. ADDITIONALLY...AFTERNOON
THUNDERSTORMS FORMING IN THE UPSLOPE REGIME OVER NORTHEAST
COLORADO AND WESTERN NEBRASKA MAY MOVE SLOW INITIALLY BEFORE
GROWING UPSCALE. THUS...THERE IS A BROAD AREA COVERED BY A SLIGHT
RISK OF EXCESSIVE RAINFALL.


...OKLAHOMA AND TEXAS...

THE CAP BUILDS THIS MORNING ACROSS SOUTHWEST KS THROUGH
CENTRAL/WESTERN OK INTO SOUTHWEST TX...SO WE TRIED TO GIVE THE
KANSAS CONVECTION A GOOD EASTWARD COMPONENT...WITH PREFERRED
DEVELOPMENT ON THE LESSER CAPPED FLANK. IT IS UNCERTAIN HOW LONG
THIS ACTIVITY WILL PERSIST IN AN ORGANIZED WAY...AS THE AXIS OF
STRONGER LOW LEVEL INFLOW REMAINS BACK WEST BENEATH THE CAP. IT IS
ALSO UNCERTAIN TO WHAT EXTENT THIS ACTIVITY MAY BUILD DOWN INTO
EASTERN OKLAHOMA. A CLUSTER OF HIGH-RESOLUTION MODELS...THE
WRF-ARW...WRF-NMM...AND NSSL WRF...ALSO BRING WIDESPREAD
CONVECTION DOWN THROUGH OKLAHOMA THIS EVENING AFTER DRYLINE
INITIATION NEAR THE NORTHWEST CORNER OF OKLAHOMA. ALTHOUGH THE
SCENARIO IS PLAUSIBLE...AND MAY BE AIDED BY THE CLOSE APPROACH OF
THE SUB-TROPICAL JET AXIS...THE CAP STRENGTH DOES CREATE SOME
UNCERTAINTY. THE MODELS HAVE GENERALLY BE TOO WIDESPREAD WITH
PRECIPITATION IN THIS PATTERN...AS THEY ALLOW STRONG CAPE TO DRIVE
THE PROCESS IN WHAT IS OTHERWISE NOT VERY STRONG BACKGROUND
ASCENT. FOR THESE REASONS...WE WERE MORE CONSERVATIVE WITH QPF
AMOUNTS OVER CENTRAL/EASTERN OKLAHOMA...BUT WILL HAVE TO
CONTINUALLY RE-EVALUATE THIS AREA FOR A POSSIBLE UPGRADE TO SLIGHT
RISK LATER TODAY. FARTHER SOUTH...THE HI-RES MODELS FEATURE ALMOST
NO QPF OVER SOUTHWEST TEXAS THIS AFTERNOON...WITH THE SUB-TROPICAL
JET NOSING OUT AND MID LEVEL TEMPERATURES BUILDING FURTHER ON THE
SOUTH SIDE OF THE JET AXIS.


...NEVADA...

BOTH GEFS PROBABILITIES AND ECMWF ENSEMBLE PROBABILITIES INDICATE
GREATER LIKELIHOOD OF
HYDROLOGICALLY SIGNIFICANT RAINFALL IN CLOSE PROXIMITY TO THE
LARGE SCALE TROUGH AXIS...FROM THE SOUTHERN
SIERRAS IN CALIFORNIA...ACROSS CENTRAL/NORTHEAST NEVADA.
PRECIPITABLE WATER VALUES THROUGHOUT THE WEST WERE NEAR OR BELOW
CLIMATOLOGICAL AVERAGE FOR LATE MAY...SO DIURNAL SHOWERS AND
THUNDERSTORMS MAY NOT BE OVERLY PRODUCTIVE. THERE IS SOME CONCERN
IN NEVADA...HOWEVER...WHERE THE NAM PAINTS AT LEAST A FEW HUNDRED
J/KG OF CAPE THIS AFTERNOON...WITH STORM MOTIONS / MEAN LAYER
WINDS VERY LIGHT AT 5 KNOTS OR LESS. HOURLY RAIN RATES APPROACHING
A HALF INCH IN THE WRF-ARW...ARE FAIRLY PERSISTENT WITH LITTLE
MOVEMENT IN THE MODEL FORECAST FOR SEVERAL HOURS...SUGGESTING
THERE COULD BE SOME ISOLATED ISSUES WITH SURFACE RUNOFF / RAINFALL
APPROACHING FLASH FLOOD GUIDANCE VALUES.

BURKE
$$




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