MESOSCALE PRECIPITATION DISCUSSION 0184
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
329 PM EDT SAT MAY 07 2016
 
AREAS AFFECTED...CENTRAL WYOMING 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 071929Z - 072229Z
 
SUMMARY...REISSUING MPD FOR STRONGER WORDING AS FLASH FLOOD RISK
APPEARS TO HAVE ESCALATED ALONG WIND RIVER RANGE...AND PERHAPS IN
ADJACENT AREAS. SOME FLASH FLOODING NOW LIKELY.

DISCUSSION...VERY CONCERNED OVER RADAR TRENDS IN CENTRAL
WYOMING...ESPECIALLY AREAS ALONG HIGHWAYS 287 AND 26 FROM LANDER
TO CROWHEART. WITH WEAK UPSTREAM INSTABILITY AND ANOMALOUS 700 MB
EASTERLY FLOW...THE SITUATION BETTER RESEMBLES SOME OF THE FOCUSED
UPSLOPE FLASH FLOOD EVENTS MORE COMMONLY SEEN ALONG THE FRONT
RANGE IN COLORADO. CONVECTION OCCURRING WEST OF RIVERTON WAS CLOSE
ENOUGH TO THE RADAR THAT BEAM HEIGHT WAS BELOW THE MELTING
LEVEL...SUGGESTING HIGH REFLECTIVITES WERE NOT ASSOCIATED WITH
BRIGHT BANDING...AND CONFIRMED BY HEAVY RAIN DUAL-POL
CLASSIFICATION. THUS...THE NEARLY 1.5 INCH PER HOUR RATES
ESTIMATED BY RADAR APPEAR BELIEVABLE...AND HAD ALREADY BEEN
ANCHORED FOR 2 TO 3 HOURS IN THE UPSLOPE REGION ALONG THE EAST
SIDE OF THE WIND RIVER RANGE. FLASH FLOOD GUIDANCE HAD ALREADY
BEEN LOWERED BY RECENT RAINFALL AND SHOULD BE EASILY SURPASSED.

WITH A PRONOUNCED SHORTWAVE COMING UP FROM COLORADO...RAP AND GFS
FORECASTS MAINTAIN ENHANCED EASTERLY FLOW THROUGH ABOUT
00Z...ANOTHER 4 TO 5 HOURS. SEEMINGLY THE ONLY LIMITING FACTOR MAY
BE CONVECTIVE OUTFLOWS ADVANCING FROM THE SOUTH...BUT THUS FAR
OUTFLOWS WERE GENERATING NEW PRECIPIATION RATHER THAN DISLODGING
IT. HRRR SIMULATED REFLECTIVITY MAINTAINS PRECIPITATION THROUGH AT
LEAST 00Z. GIVEN THE SUSTAINED UPSLOPE FLOW AND SUPPORTIVE UPPER
LEVEL LIFT...A SEVERAL HOUR PERIOD OF MODERATE AND LOCALLY HEAVY
RAINFALL IS LIKELY TO PRODUCE FLASH FLOODING...SOME OF WHICH COULD
BE SIGNIFICANT.

BURKE

ATTN...WFO...CYS...RIW...

ATTN...RFC...CBRFC...MBRFC...NWRFC...

LAT...LON   44040974 43750868 42480658 41650622 41360686 
            41590794 41950872 42910961 43621005