MESO: Mesoscale Discussion 1795

ACUS11 KWNS 190103
SWOMCD
SPC MCD 190103
WIZ000-IAZ000-MNZ000-SDZ000-190400-

MESOSCALE DISCUSSION 1795
NWS STORM PREDICTION CENTER NORMAN OK
0803 PM CDT SAT AUG 18 2007

AREAS AFFECTED...PORTIONS SRN NM...EXTREME NRN IA...SERN SD...SWRN
WI.

CONCERNING...HEAVY RAINFALL

VALID 190103Z - 190400Z

POTENTIAL FOR HEAVY RAINFALL EVENT IS INCREASING ALONG WITH
CONVECTIVE COVERAGE ACROSS PORTIONS SRN MN...WITH SOME BACKBUILDING
POSSIBLE INTO PARTS OF SERN SD N OF FSD. ACTIVITY THEN WILL
CONTINUE TO TRAIN ALONG AXIS OF ONGOING CONVECTIVE PLUME INTO SWRN
WI. ADDITIONAL DEVELOPMENT ALSO IS POSSIBLE AFTER ABOUT 03Z OVER
NRN IA N OF SFC WARM FRONT DESCRIBED BELOW. EXPECT GRADUAL
INTENSIFICATION OF TSTMS AND ACCOMPANYING PRECIP PRODUCTION...WITH
1-2 INCH/HR RATES POSSIBLE LATE THIS EVENING.

SFC MESOANALYSIS SHOWS WEAK FRONTAL-WAVE LOW OVER SERN SD VICINITY
MHE...WITH WARM FRONT ESEWD ACROSS NWRN/CENTRAL/SERN IA. WARM FRONT
SHOULD DRIFT NWD OVER SERN SD AND NERN IA AHEAD OF EWD DRIFT OF SFC
WAVE...WHILE TO ITS NE...ALREADY STRONG LOW LEVEL WAA REGIME
INTENSIFIES FURTHER. THRU 06Z...LLJ IS FCST TO STRENGTHEN AND VEER
GRADUALLY ACROSS THIS REGION...BECOMING CONFLUENT AND SWLY-WSWLY AT
35-40 KT. THIS WILL BE ASSOCIATED WITH INTENSIFYING ISENTROPIC
ASCENT IN A SLAB ALIGNED PARALLEL TO AND NE OF SFC WARM FRONT AND
VERY NEAR 850 MB FRONTAL ZONE. PROSPECTIVE INFLOW AIR -- NOW
UPSTREAM ACROSS PORTIONS IA/NEB -- IS CHARACTERIZED BY RICH SFC-600
MB MOISTURE PER OAX RAOB AND RUC FCST SOUNDINGS..WITH PW IN 1.75-2
INCH RANGE. GPS PW MEASUREMENTS INDICATE HIGHEST VALUES ATTM ACROSS
NEB/IA BORDER REGION N OMA AND UPSTREAM FROM N-CENTRAL IA/S-CENTRAL
MN. FCST TRAJECTORIES SUGGEST SOME MOISTURE FROM REMNANTS OF TC
ERIN ALSO MAY BE PART OF THIS PLUME...TRANSPORTED NEWD BENEATH
SUFFICIENTLY STEEP MID-UPPER LEVEL LAPSE RATES TO SUPPORT ELEVATED
MUCAPES 1500-2000 J/KG.

REF WW 615 AND SUBSEQUENT MESOSCALE DISCUSSIONS REGARDING NEAR-TERM
SVR POTENTIAL JUST S AND SW OF THIS AREA.

.EDWARDS.. 08/19/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MKX...ARX...MPX...DMX...FSD...

43359482 43459628 43739673 44359652 44949537 44859329
44579219 43308967 42768991 43149146 43269324

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