WPC Met Watch |
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Mesoscale Precipitation Discussion: #0431 (2018) |
(Issued at 456 PM EDT WED JUL 11 2018
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MPD Selection |
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MESOSCALE PRECIPITATION DISCUSSION 0431
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
456 PM EDT WED JUL 11 2018
AREAS AFFECTED...WY...EXT NORTHWEST CO...EXT NORTHEAST UT...
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 112100Z - 120300Z
SUMMARY...CONFLUENCE OF STREAMS AND INCREASING
MOISTURE/INSTABILITY SUGGESTS UPSCALE GROWTH INTO CONVECTIVE
CLUSTER CAPABLE OF PRODUCING FLASH FLOODING CONDITIONS.
DISCUSSION...PEAK HEATING ACROSS TERRAIN OF UNITA/WIND
RIVER/LARAMIE RANGES IS FEEDING OF MODEST INSTABILITY AND MOUNTAIN
WIND ACCELERATION/CONVERGENCE. SFC TDS IN THE CENTRAL PORTIONS OF
WY ARE IN THE MID-50S AND WHILE LOW TO MID-LEVEL IS GENERALLY WEAK
AT THIS TIME...IT IS ALSO GENERALLY CONFLUENT FROM SW WY TO NE WY.
THIS IS ALSO COINCIDENT WITH DEFORMATION/SHEAR ZONE IN THE
MID-LEVELS SUGGESTING SLIGHTLY STEEPER MID-LEVEL LAPSE RATES FOR
STRONG UPDRAFT STRENGTHS. GIVEN THE WEAK STEERING FLOW CELLS ARE
GENERALLY EXPECTED TO BE VERY SLOW MOVING ALLOWING FOR THE MODEST
RAIN RATES (IN THE 1.5-2"/HR RANGE) TO INCREASE IN TOTALS. CELLS
WILL ALSO BE EVACUATED WELL LYING WITHIN THE RIGHT ENTRANCE TO
STRENGTHENING 3H JET UP TO 50KTS IN SE WY. IT IS THIS BROAD
SYNOPTIC ISENTROPIC ASCENT FROM CENTRAL UT ACROSS WY INTO THE
STRENGTHENING JET THAT WILL ALSO PROVIDE MOISTENING OF THE
MID-LEVELS AS TRENDING IN THE CIRA LPW FROM 7-3H LAYERS KEEPING
RAINFALL EFFICIENCY FAIRLY HIGH TO MAINTAIN THE CLUSTERS AS THE
COMPLEX GROWS UPSCALE.
SURFACE FRONT APPEARS TO BE DRAPED ACROSS S WY AT THIS TIME
ANGLING TOWARD NW NEB INTO CENTRAL SD. STRENGTHENING MOISTURE FLUX
IN THE UPSLOPE FLOW REGIME FROM THE SOUTHEAST WILL ALSO BE
ENHANCED WITH FLUX ALONG A FAIRLY MOIST COOL CONVEYOR BELT
INCREASING TO 14-20KTS AFTER 00Z ACROSS NE WY. THIS SHIFT IN FLOW
REGIME IN THE LOWER LEVELS WILL ALSO SUPPORT CLOUD BEARING VECTORS
TO CONVERGE ACROSS CENTRAL WY SUGGESTIVE OF CELL/CLUSTER MERGERS
ARE POSSIBLE AFTER 00Z ONLY ADDING TO THE SW-NE TRACK OF
CLUSTER/COMPLEX. THIS IS GENERALLY FALLING IN LINE WITH RECENT
HRRR RUNS AS WELL AS THE HRRR-TLE SUGGESTING 2-3" TOTALS OVER
SHORT TIME SCALES LEADING TO POSSIBLE FLASH FLOODING THROUGH 03Z.
GALLINA
ATTN...WFO...CYS...GJT...RIW...SLC...UNR...
ATTN...RFC...CBRFC...MBRFC...
LAT...LON 44300446 43320449 41250732 40470872 40481032
41071102 42590977 44100697
Last Updated: 456 PM EDT WED JUL 11 2018
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