Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 190058
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
857 PM EDT MON MAY 18 2015

...VALID 01Z TUE MAY 19 2015 - 12Z TUE MAY 19 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 S LIC 30 S SPD 35 NW PVW 50 NNE SNK 25 ESE JCT 20 E COT
20 ENE LRD 25 WNW MMNL 35 WSW MMPG 35 WNW INK 25 N CQC AFF
25 S LIC.


...SOUTHERN ROCKIES/SOUTHERN HIGH PLAINS/TX PANHANDLE...

AN ANOMALOUS UPPER TROUGH AND DYNAMIC JET STREAK WILL SWEEP
THROUGH THE DESERT SOUTHWEST TOWARD THE FOUR CORNERS REGION. THE
COMBINATION OF CONFLUENT UPPER FLOW ALOFT SETTING UP OVER THE NRN
PLAINS/UPPER MIDWEST AND SLIGHT NEG TILT IN THE SRN STREAM TROUGH
IS SUGGESTING THE POTENTIAL FOR ORGANIZED HEAVY SYNOPTIC SCALE
PRECIP LATE TODAY/OVERNIGHT. THE UPPER FLOW WILL BECOME
INCREASINGLY MORE DIFFLUENT ACROSS THE SOUTHERN ROCKIES/HIGH
PLAINS REGION... AS A LLJ IS FORECAST TO PICK UP STEAM WITH 2O TO
30 KNOT SOUTHEASTERLY FLOW IMPINGING ON THE LOCAL TERRAIN OF
NM/CO. THIS SURGE OF UPSLOPE FLOW IN CONJUNCTION WITH STRONG
MID/UPPER FORCING SUPPORT FAIRLY HEAVY RAINFALL ACROSS EASTERN NM
INTO SOUTHEASTERN CO AND EVENTUALLY SPREADING OUT INTO THE TX
PANHANDLE. HEFTY RAINFALL RATES COMBINED WITH POTENTIALLY SLOW
CELL MOTIONS SUPPORT A RISK FOR FLASH FLOODING.


...PORTIONS OF WEST TEXAS EAST-SOUTHEAST OF THE BIG BEND...

THERE IS A GOOD SIGNAL IN THE MORE RECENT HIGH RESOLUTION GUIDANCE
OF HEAVY TO POTENTIALLY EXCESSIVE RAINFALL ACROSS WEST TX E-SE OF
THE BIG BEND OVERNIGHT...STEMMING FROM THE CONVECTION CURRENTLY
ORGANIZING ACROSS NE MEXICO LATE THIS AFTERNOON IN A
BROADLY-DIFFLUENT UPPER FLOW PATTERN AHEAD OF THE CLOSED LOW
ACROSS THE SOUTHWEST. MUCAPES LATE THIS AFTN AREA QUITE
IMPRESSIVE... 4000-5000 J/KG...UNTAPPED UP TO THIS POINT HOWEVER
GIVEN THE CAPPING PROFILE ~700 MB. OVERNIGHT THE SOUTHEASTERLY LOW
LEVEL INFLOW INCREASES TO AROUND 40 KTS BY 06Z...THEN VEERS SOUTH
30-40 KTS BY 12Z. THIS WILL HELP TO POOL PWS OF 1.75+ INCHES
ACROSS WEST TEXAS...WHILE ALSO PROMOTING SOUTHEASTERLY CORFIDI OR
MBE VECTORS DIRECTLY INTO (OPPOSED TO) THE LOW LEVEL INFLOW. THE
GUIDANCE IS CONSISTENT WITH THE DEGREE OF INSTABILITY SETTLING
CLOSER TO 2000-3000 J/KG OVERNIGHT...WHICH IS STILL QUITE
FAVORABLE FOR MCS DEVELOPMENT/UPSCALE GROWTH CONSIDERING THE
DEGREE OF THERMODYNAMIC SUPPORT. THE 12Z WRF-ARW (AND PARALLEL
VERSION)...NAM CONEST...AND LATEST RAP AND HRRR RUNS ALL SHOW A
SIGNAL FOR POTENTIALLY SIGNIFICANT RAINFALL ACROSS THIS REGION
OVERNIGHT INTO EARLY TUE.


...NY/PA...

AN UPPER RIDGE CURRENTLY STRETCHING UP THE ENTIRE EXTENT OF THE
EASTERN U.S. WILL BEGIN TO GIVE WAY IN RESPONSE TO UPSTREAM HEIGHT
FALLS. AHEAD OF THE ADVANCING UPPER TROF...THE SOUTHWESTERLY
MID-LEVEL FLOW IS EXPECTED TO PICK UP SOME SPEED WITH MODELS
DEPICTING 25 TO 30 KNOT WINDS OVERSPREADING THE REGION. THIS WOULD
AT LEAST SUPPORT BETTER ORGANIZATION IN INDIVIDUAL STORM
STRUCTURES ACROSS THE STATE. MOISTURE ADVECTION WILL NOT BE AN
ISSUE AS ABOVE 1.50 INCH PWATS LIFT NORTHWARD AHEAD OF A
PRE-FRONTAL SHORTWAVE TROF... IN FACT BUF HAD ALMOST A RECORD
OBSERVED PW THIS MORNING. EXPECT CONVECTION WILL BE DRIVEN BY
DIURNAL HEATING WITH INSTABILITY RISING INTO THE 500 TO 1000 J/KG
RANGE IN THE AFTERNOON. THIS SHOULD ALLOW SCATTERED TO WIDESPREAD
CONVECTION TO AFFECT CENTRAL TO UPSTATE NY INTO CENTRAL/NERN PA
WITH STORM MOTIONS AROUND 5 KNOTS TOWARD THE EAST-SOUTHEAST. THESE
SLOWER CELL MOTIONS COMBINED WITH LOWER FFG VALUES AFFORDED A SEE
TEXT THREAT AREA ON THE LATEST EXCESSIVE RAINFALL FORECAST.


...TN VALLEY...

DESPITE THE LIMITED 0-6 KM BULK SHEAR (GENERALLY UNDER 20
KTS)...ANTICIPATE THE CURRENT SCT CONVECTION LATE THIS AFTERNOON
TO BECOME BETTER ORGANIZED (MORE WIDESPREAD) AHEAD OF THE MCV
CURRENTLY ACROSS NW GA. DEEP-LAYER RIDGING AND OVERALL WARM
PROFILE ALOFT IS LIMITING THE DEEP LAYER INSTABILITY (MUCAPES
GENERALLY 1000-2000 J/KG)...THOUGH GIVEN SOME OF THE LOWER FFG
VALUES IN THE AREA (1.5-2.0 INCHES WITHIN 3 HOURS)...ALONG WITH
THE THERMODYNAMIC PROFILE (PWS AROUND 1.75")...SHORT-TERM RAINFALL
RATES COULD LOCALLY EXCEED THE FFG.


...NV/OR...

IMPRESSIVE CLOSED UPPER LOW OVER NORTHERN/CENTRAL CA COAST THIS
MORNING WITH A DYNAMIC UPPER JET STREAK IN THE BASE OF THE UPPER
TROUGH ARRIVING INTO THE DESERT SOUTHWEST. WATER VAPOR IMAGERY
THIS MORNING SHOWS ALMOST IDEAL UPPER DIFLUENT PATTERN IN BETWEEN
THE TWO FEATURES IN DEEP SRLY TO SERLY FLOW... FROM NV/UT
SPREADING NORTH AND WEST INTO OR/SRN ID. THE MOISTURE CONTENT IS
NOT OFF THE CHARTS WITH PWS THIS MORNING RANGING FROM .75 OF AN
INCH TO AN INCH BUT WITH ENOUGH MID/UPPER FORCING ANTICIPATED AND
LIGHT STEERING FLOW OVERALL... THIS COL-AREA COULD BECOME
SUSCEPTIBLE TO ORGANIZED LINE SEGMENTS OF ISOLATED HEAVY RAINFALL.

MUSHER/HURLEY
$$




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