Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 230056
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
853 PM EDT FRI MAY 22 2015

...VALID 01Z SAT MAY 23 2015 - 12Z SAT MAY 23 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
DTO 15 SE MWL 25 NW SEP 30 ESE ABI 15 SSW DYS 25 SSW SWW
10 SE BPG 10 ENE MDD 25 WNW ODO 35 SE CNM 20 SW CNM 20 WSW ATS
10 WNW ROW 50 ENE 4CR 25 WNW TCC 10 WNW DHT DUX 20 WSW PPA
45 SSE HHF 30 W CHK 10 S OUN 10 S ADH 15 SSW DUA DTO.


...SOUTHERN ROCKIES INTO THE SOUTHERN PLAINS...
EARLIER THINKING STILL ON TRACK HERE.  THE UPPER LOW DIGS INTO THE
SOUTHWEST AND HEIGHTS BEGIN TO RISE ACROSS THE SOUTHERN PLAINS.
THERE IS POTENTIAL FOR MCS DEVELOPMENT OVERNIGHT...AS THE UPPER
LOW PIVOTS INTO THE 4 CORNERS REGION AND THE UPPER FLOW ACROSS THE
SOUTHERN ROCKIES INTO THE SOUTHERN PLAINS BECOMES INCREASINGLY
DIFFLUENT. THE MODELS SHOW MODEST BROAD-SCALE UPPER DIVERGENCE
DEVELOPING ACROSS THE SOUTHERN ROCKIES AND TX PANHANDLE EASTWARD
THROUGH THE RED RIVER VALLEY IN NORTH TX/SOUTHERN OK...THOUGH
SUSPECT THE ROBUST UVVS NOTED FROM SOME OF THE NWP (GFS IN
PARTICULAR) ARE INDICATIVE OF THE MODEL DEVELOPING AN MCS. THE LOW
LEVEL S/SSW INFLOW INCREASES TO 40-50 KTS... MUCAPES CLIMB TO
1000-1500 J/KG...AND PW ANOMALIES RISE TO AROUND 2 STANDARD
DEVIATIONS ABOVE NORMAL. THE WRF-ARW...WRF-NMMB...AND NSSL-WRF
SIMULATED REFLECTIVITY GUIDANCE SUGGEST A GENESIS REGION ACROSS
EASTERN NEW MEXICO ALONG AND NORTH OF THE SURFACE WARM FRONT
BETWEEN 00-06Z...WITH THE ACTIVITY AND WARM FRONTAL BOUNDARY
LIFTING NE/ENE THROUGH 12Z.  SOME LOCALIZED RAINFALL AMOUNTS OF
2+ INCHES WITHIN A 6 HOUR PERIOD WILL BE POSSIBLE.


...NORTHEAST OREGON/SOUTHEASTERN WA...

AS THE DEEP UPPER LOW PIVOTS INTO THE SOUTHWEST AND 4 CORNERS
REGION DURING THE DAY 1 PERIOD...THE UPPER PATTERN ACROSS THE
ENTIRE WESTERN CONUS WILL REMAIN STRONGLY MERIDIONAL WITH SOMEWHAT
OF A REX-BLOCKING SIGNATURE AS A CLOSED 570 DM 500 MB HIGH FORMS
ACROSS WESTERN CANADA AND EVENTUALLY DROPS INTO THE NORTHERN GREAT
BASIN BY THE END OF THE PERIOD. A SHARPENING DEFORMATION/SHEAR
AXIS AT MID LEVELS DEVELOPS ALONG THE WEST COAST BETWEEN THE 500
MB RIDGE ACROSS THE PACIFIC AND THE AFOREMENTIONED 500 MB HIGH
THAT PINCHES OFF ACROSS WESTERN CANADA AND THE NORTHERN GREAT
BASIN. THIS UNUSUAL DYNAMICAL SETUP ALONG WITH THE ANOMALOUS
THERMODYNAMIC PROFILE (MUCAPES INCREASING TO 1000-1500 J/KG DURING
THE AFTN/EVENING ALONG WITH PWS AOA 0.75 INCH) WILL MAKE FOR
LOCALLY HEAVY/POTENTIALLY EXCESSIVE OROGRAPHICALLY-ENHANCED
RAINFALL ALONG AND NEAR THE BLUE MTNS OF NORTHEAST OREGON.  24
HOUR AREAL-AVERAGE RAINFALL AMOUNTS ARE EXPECTED TO RANGE BETWEEN
.50 AND 1.00 INCH ACROSS THE AREA PER A MULTI-MODEL
BLEND...HOWEVER...PER THE HIGH RESOLUTION GUIDANCE...LOCALLY
HIGHER AMOUNTS BETWEEN 1-3+ INCHES WITHIN A 3-6 HOUR PERIOD WILL
CAUSE RUNOFF ISSUES GIVEN THE RELATIVELY LOW FFG.


...HIGH PLAINS OF NORTHEAST CO/WESTERN NEBRASKA/SOUTHEAST WY...

DURING THE OVERNIGHT PERIOD...THE UPPER LEVEL PATTERN BECOMES MORE
AMPLIFIED AS THE DEEP UPPER LOW SHIFTS INTO THE 4 CORNERS REGION
WHILE THE DOWNSTREAM RIDGE BUILDS (HEIGHTS RISE ACROSS THE EASTERN
PLAINS AND MID/UPPER MS VLY). THE INCREASING UPPER LEVEL
DIFFLUENCE ALONG WITH 850 MB S/SW FLOW INCREASING TO 40-50 KTS
WILL AGAIN BOOST THE S-N LOW-MID LAYER MOISTURE TRANSPORT AND
MODEST DEEP LAYER INSTBY (MUCAPES 500-1000 J/KG) INTO THE CENTRAL
PLAINS OVERNIGHT.  A FEW ADDITIONAL SHOWERS AND STORMS MAY DEVELOP
OVER AREAS WHERE RAINS OCCURRED THIS MORNING...POTENTIALLY CAUSING
SOME RUNOFF PROBLEMS.

TERRY/PETERSEN/HURLEY


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