Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 222102
QPFERD

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

...VALID 2101Z FRI MAY 22 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...
MADE ONLY VERY MINOR CHANGES HERE..MAINLY TO EXTEND THE PREVIOUS
ISSUANCE A BIT SOUTH THRU THE
TX HIGH PLAINS/NM.  OTHERWISE..EARLIER THINKING STILL ON TRACK.
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. WPC UTILIZED A MULTI-MODEL BLEND WITH
THE QPF...THE BULK OF WHICH WAS BASED WITH 00Z ECMWF GUIDANCE
WHICH WAS SUPPORTED BY THE 00 NSSL-WRF OUTPUT. AREAL-AVERAGE QPF
BETWEEN .25 AND 1.00 INCH WAS NOTED OVER A BROAD AREA...HOWEVER AS
PER THE HIGH RESOLUTION GUIDANCE...LOCALIZED AMOUNTS BETWEEN 2-4+
INCHES WITHIN A 6 HOUR PERIOD WILL BE POSSIBLE.


...NORTHEAST OREGON...

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. THE 00Z NAM
CONEST WAS PARTICULARLY ROBUST... WITH ISOLATED MAXIMA OF 5+
INCHES NOTED.


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

A SHORTWAVE LIFTING NORTHEAST IS ENHANCING IN WAA FORCING
(STRENGTHENING LOW-LEVEL INFLOW AND MOISTURE TRANSPORT ALONG WITH
DEEPENING ISENTROPIC ASCENT).  WIDESPREAD AREAS OF RAIN ACROSS
NORTHEAST CO INTO ADJACENT KS/WY/SD WILL LIFT NORTHEAST AS TODAY
PROGRESSES.
EXPECT MODERATE RAINFALL TOTALS...ESPECIALLY EARLY THIS
MORNING...AS AREAL-AVERAGE AMOUNTS RANGE BETWEEN .25 TO .75 INCH
ACROSS MUCH OF THE AREA.

LATER IN THE PERIOD (00-12Z SAT)...THE UPPER LEVEL PATTERN BECOMES
EVEN 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 INCREASE
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 SO
THE AREA WILL BE MONITORED FOR POTENTIAL FOR RAINFALL TO PRESENT
RUNOFF PROBLEMS.

TERRY/PETERSEN/HURLEY


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