THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXCESSIVE RAINFALL DISCUSSION


[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]



EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
437 AM EDT TUE MAY 24 2016

...VALID 12Z TUE MAY 24 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
20 SW ODX 30 NNE CSQ 10 SE OTM 20 ENE IRK 25 SE DMO 35 NNW UNO
30 NW AWM SGT 35 N RUE 10 E PPF 10 SSE RSL 20 SE AKO 35 SSW IBM
20 NNW SNY 40 NW LBF 20 SW ODX.


...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




Last Updated: 437 AM EDT TUE MAY 24 2016