MESO: Mesoscale Discussion 0541

ACUS11 KWNS 222259
SWOMCD
SPC MCD 222259
MOZ000-IAZ000-MNZ000-SDZ000-NEZ000-230100-

MESOSCALE DISCUSSION 0541
NWS STORM PREDICTION CENTER NORMAN OK
0559 PM CDT SUN APR 22 2007

AREAS AFFECTED...PORTIONS NWRN/N-CNTRL MO...CENTRAL IA...SWRN SD AND
NWRN IA.

CONCERNING...TORNADO WATCH 164...

VALID 222259Z - 230100Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 164 CONTINUES.
HOWEVER...WW MAY BE CANCELED BEFORE SCHEDULED 2Z EXPIRATION.

PRIMARY BAND OF BOUNDARY LAYER CONVERGENCE WAS EVIDENT AT 2230Z FROM
NEAR STJ NNEWD THROUGH CENTRAL IA...PARALLEL TO AND ROUGHLY 30 NM W
OF I-35. NARROW WINDOW OF OPPORTUNITY REMAINS FOR THIS ACTIVITY TO
PRODUCE SVR HAIL...GUSTS AND PERHAPS A TORNADO OR TWO BEFORE MOVING
INTO AIR MASS CHARACTERIZED BY MORE STABLE SFC PARCELS. CONVECTIVE
POTENTIAL WILL DIMINISH CONSIDERABLY BEHIND THIS LINE AS BOUNDARY
LAYER FLOW VEERS...IN RESPONSE TO NEWD LIFT OF STRONGEST ISALLOBARIC
FORCING ACROSS ERN IA...SERN MN AND WI. THIS PROCESS WILL REDUCE
BOTH SHEAR AND CONVERGENCE IN LOW LEVELS. THEREFORE WW MAY BE
CLEARED FROM W-E ACROSS IA BEHIND INITIAL BAND OF CONVECTION.
MEANWHILE...FARTHER NW ACROSS NWRN IA AND SERN SD...A FEW STG CELLS
LINGER WITHIN CLUSTER OF CONVECTION AND PRECIP BENEATH COLD-CORE
VORTEX ALOFT. BRIEF/SMALL TORNADO CANNOT BE RULED OUT DURING NEXT
1-2 HOURS FROM DISCRETE ACTIVITY JUST SW-SE OF FSD. WITH
TIME...HOWEVER...REDUCTION IN SFC HEATING -- RELATED BOTH TO
WEAKENING INSOLATION AND TO STABILIZATION FROM PRECIP -- LIKEWISE
WILL DIMINISH BUOYANCY ENOUGH TO REMOVE SIGNIFICANT CONVECTIVE
POTENTIAL.

.EDWARDS.. 04/22/2007

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

ATTN...WFO...DMX...EAX...FSD...OAX...

39829481 40589443 42129409 42769425 43139471 43259572
42959651 42889674 42859756 42829798 43049811 43249790
43489680 43529560 43329443 42469376 39569328 39629469

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