Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 220041
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
841 PM EDT SAT MAY 21 2016

...VALID 01Z SUN MAY 22 2016 - 12Z SUN MAY 22 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...



22/0100 UTC UPDATE...


...MOUNTAINS OF NRN ID/MT...
FOR THE REMAINDER OF THE NIGHT...MID/UPR CIRC NEAR THE OREGON/ID
BORDER WILL GIVE WAY TO A DVLPG CIRC OVER WRN MT OVERNIGHT WITH
MODELS INDICATING AN INTENSIFYING COMMA HEAD BAND THAT WILL BRING
MDT TO LOCALLY HEAVY RAINS ACRS NRN PORTIONS OF ID/NW MT DURING
THE REMAINDER OF THE NIGHT. 18Z NAM FORECAST SOUNDING INDICATE
SATURATED CONDS THROUGH A DEEP LAYER WITH SOME WEAK INSTABILITY
EARLY IN THE PD THAT COULD LEAD TO SOME EMBDD CONVECTIVE ELEMENTS.
 SOME OF THE HI RES MODEL GUIDANCE FROM THE 12Z RUNS LOOK A BIT ON
THE HIGH END  WITH AMOUNTS..BUT SOME OF THE RECENT HRRR RUNS
SUGGEST POTNL FOR ISOLD 1 TO 1.5 INCH RAINS.

ELSEWHERE...NO CHANGE TO SEE TEXT AREA OVER KS/OK/TX     SULLIVAN
 PREVIOUS DISCUSSION FOLLOWS...



...DRY LINE CONVECTION IN KS/OK/TX...

THE UPPER AIR PATTERN WILL MOVE EVER SO SLIGHTLY EASTWARD
TODAY...BRINGING FALLING PRESSURES OVER THE HIGH PLAINS AND
CENTRAL TO NORTHERN ROCKIES...WHICH WILL DRAW INCREASINGLY MOIST
AIR UP INTO THE AREA FROM SOUTHWEST KANSAS TO THE TEXAS PANHANDLE.
FORCING FOR ASCENT WILL NOT BE STRONG...BUT GIVEN THE STRONG SUN
ANGLE AND SUFFICIENTLY DIFLUENT UPPER FLOW...SCATTERED
THUNDERSTORMS SHOULD FORM AHEAD OF A SURFACE DRY LINE. STORM SCALE
PROCESSES MAY DOMINATE...SO IT IS DIFFICULT TO OUTLINE AN
ORGANIZED FLASH FLOOD THREAT. BUNKERS MOTION FOR RIGHT MOVING
SUPER CELLS IS PREDICTED AT ONLY 5 KNOTS...HOWEVER...SO SLOW CELL
MOTIONS AND SUSTAINED SOUTHERLY INFLOW DURING THE
EVENING/OVERNIGHT COULD YIELD RAINFALL APPROACHING OR EXCEEDING
FLASH FLOOD GUIDANCE IN ISOLATED LOCATIONS.


...MOUNTAIN AREAS OF NORTHERN ID/MT...

WEAK INSTABILITY WILL DEVELOP THIS AFTERNOON DURING THE APPROACH
OF A VORTICITY CENTER AND COLD CORE SYSTEM LIFTING UP FROM THE
SOUTH. THE WPC AREAL AVERAGE QPF PREDICTS 0.75 INCHES OR MORE OF
PRECIPITATION IN PARTS OF NORTHERN ID/MT...AND HI-RESOLUTION
MODELS INDICATE SPOTTY HEAVIER TOTALS. CELL MOTIONS COULD BE VERY
SLOW...WITH 0-6 KM MEAN WIND SPEEDS ONLY 5 KNOTS PER THE GFS.
INSTABILITY IN THE MODELS IS MINIMAL...BUT COULD BE BOLSTERED BY
BREAKS IN THE CLOUDS AND STRONG MAY SUN ANGLE AT HIGH ELEVATIONS.
ANOTHER FACTOR TO CONSIDER TODAY IS THE SNOW-MELT SEASON WHICH IS
ALREADY EXPECTED TO CAUSE FAST RIVER FLOWS AND MAY PUSH SOME
RIVERS TO ACTION STAGE PER THE WFO MSO HYDROLOGIC OUTLOOK AND NWS
AHPS DATA. THUS...THE ADDITIONAL RAINFALL COULD CAUSE SOME LOCAL
RAPID RUNOFF...ALTHOUGH THE ODDS OF EXCEEDING FLASH FOOD GUIDANCE
AT ANY GIVEN LOCATION STILL APPEAR TO BE ON THE LOW SIDE.

BURKE
$$




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