SWODY1
SPC AC 181950
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0250 PM CDT FRI MAY 18 2007
VALID 182000Z - 191200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ND AND NRN
MN...
..ND/MN...
WEAK MID LEVEL IMPULSE MOVING EWD INTO ERN MT IS EXPECTED TO TRACK
ACROSS ND THIS EVENING AND REACH NRN MN LATE TONIGHT. EARLY
AFTERNOON SURFACE ANALYSIS SHOWED A COLD FRONT EXTENDING FROM NW
ONTARIO SWWD THROUGH EXTREME SERN MANITOBA TO ALONG THE MANITOBA/ND
BORDER INTO SRN SASKATCHEWAN. OBJECTIVE ANALYSES INDICATED AIR MASS
ALONG/S OF THIS BOUNDARY HAS BECOME MODERATELY UNSTABLE...WITH
ADDITIONAL DESTABILIZATION EXPECTED AS SURFACE TEMPERATURES CONTINUE
TO RISE INTO THE 80S WITHIN MOIST ENVIRONMENT AND BENEATH STEEP
LAPSE RATES.
VISIBLE IMAGERY INDICATED AN AREA OF ACCAS/CU FIELD DEVELOPING OVER
SERN SASKATCHEWAN NEAR THE COLD FRONT...WITH SOME CU ALSO DEVELOPING
IN NW ND. THESE CLOUDS SUGGEST THIS AIR MASS MAY BE STARTING TO
RESPOND TO FORCING FOR ASCENT AHEAD OF THE ERN MT IMPULSE. AS THE
IMPULSE PROGRESSES EWD THIS FORECAST PERIOD...TSTMS SHOULD DEVELOP
BY LATE THIS AFTERNOON INTO NRN ND AS THE FRONT MOVES SWD.
EFFECTIVE BULK SHEAR VALUES ARE ALREADY STRONG ENOUGH FOR ORGANIZED
MULTICELLS AND SUPERCELLS ACROSS NRN ND. THEREFORE...ONCE STORMS
DEVELOP...THEY SHOULD BECOME SEVERE WITH HAIL AND DAMAGING WINDS
BEING THE MAIN THREATS. SEVERE WEATHER THREAT IS EXPECTED TO SPREAD
EWD ACROSS ND INTO MN DURING THE EVENING...WITH POTENTIAL FOR AT
LEAST ISOLATED SEVERE STORMS TO PERSIST THROUGH LATE TONIGHT ACROSS
NRN MN.
..MT...
TSTMS WILL CONTINUE TO DEVELOP FROM SWRN INTO SRN MT THIS AFTERNOON.
THIS ACTIVITY WILL BE LOCATED ALONG/S OF A SURFACE FRONT EXTENDING
FROM NE TO SW MT. ALTHOUGH THE AIR MASS S OF THE FRONT HAS BECOME
MODERATELY UNSTABLE...STRONGER DEEP LAYER SHEAR FOR ORGANIZED STORMS
IS EXPECTED TO REMAIN ALONG/N OF THE BOUNDARY. STORMS NEAR THE
FRONT MAY BECOME ORGANIZED...BUT OVERALL SEVERE WEATHER THREAT
SHOULD REMAIN TOO LOW TO WARRANT HIGHER SEVERE PROBABILITIES AND A
CATEGORICAL RISK.
..CENTRAL/SRN FL PENINSULA...
TSTMS WILL CONTINUE TO DEVELOP ALONG 1. A FRONT MOVING SWD THROUGH
CENTRAL FL...2. WEST/EAST COAST SEA BREEZE BOUNDARIES...AND 3. ANY
OTHER BOUNDARY INTERSECTIONS. MODERATELY UNSTABLE AIR MASS WILL
SUPPORT A FEW VIGOROUS UPDRAFTS WITH ISOLATED STRONG GUSTY WINDS AND
HAIL BEING THE PRIMARY THREATS. FOR MORE INFORMATION ON THE
MESOSCALE DETAILS...PLEASE REFER TO SPC MESOSCALE DISCUSSION NUMBER
827 FOR PORTIONS OF THE CENTRAL/SRN FL PENINSULA
..SERN AZ/SRN NM/SW TX...
GIVEN WEAK UPPER FORCING...STRONG SURFACE HEATING AND STEEP LAPSE
RATE ENVIRONMENT WILL CONTINUE TO SUPPORT TSTM DEVELOPMENT PRIMARILY
IN THE HIGHER TERRAIN OF ERN AZ/NM AND EVENTUALLY ACROSS SW TX
THROUGH THIS AFTERNOON AND EVENING. WEAK DEEP LAYER SHEAR WILL
LIKELY PRECLUDE STORM ORGANIZATION. HOWEVER...MODERATE INSTABILITY
EXTENDING FROM SERN AZ THROUGH SWRN NM TO ALONG THE RIO GRANDE
VALLEY IN SW TX AND STEEP LAPSE RATES SHOULD PROVE FAVORABLE FOR
ISOLATED STRONG WIND GUSTS AND SOME HAIL.
.PETERS.. 05/18/2007
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