Thursday, April 02, 2009

4/2/09 - Day 1 Outlook SPC




Tornado probabilities within 25 miles of a point


Hail probabilities within 25 miles of a point


Damaging wind probabilities within 25 miles of a point
   DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT THU APR 02 2009

VALID 021200Z - 031200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS WRN TN...MS...AL...SRN
GA...NRN FL...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM
ERN TX INTO THE OH VALLEY AND COASTAL CAROLINAS...

...SIGNIFICANT SEVERE WEATHER EXPECTED ACROSS MUCH OF THE GULF COAST
STATES INTO THE WRN TN VALLEY...

EARLY MORNING SATELLITE/RADAR IMAGERY CLEARLY DEPICT CENTER OF UPPER
LOW OVER NERN NM NEAR TCC...DIGGING SEWD IN LINE WITH 00Z MODEL
GUIDANCE. THIS FEATURE SHOULD MOVE ALONG THE RED RIVER THIS MORNING
BEFORE EJECTING NEWD ACROSS AR INTO WRN TN DURING THE EVENING HOURS
AS 90KT+ MID LEVEL JET ROTATES INTO MS/AL. NEEDLESS TO SAY LOW
LEVEL RESPONSE TO THIS UPPER JET WILL INTENSIFY AS SFC LOW EVOLVES
OVER AR BY 18Z WITH SUBSEQUENT MOVEMENT AND DEEPENING EXPECTED INTO
WRN TN BEFORE LIFTING NEWD ALONG THE OH RIVER TONIGHT.

MARITIME AIRMASS HAS YET TO SURGE INLAND SIGNIFICANTLY ALONG THE
GULF COAST WITH GREATEST NWD MOVEMENT NOW OCCURRING ACROSS CNTRL TX
IMMEDIATELY AHEAD OF SFC FRONT...AND FARTHER EAST ACROSS PORTIONS
SRN AL/GA IN ASSOCIATION WITH NWD DRIFTING WARM FRONT. THIS LATTER
FEATURE MAY NOT LOOSE ITS IDENTITY AS CONVECTION DEVELOPS
ALONG/NORTH OF THE WIND SHIFT THROUGH THE PERIOD.

LATEST THINKING IS MOISTURE/INSTABILITY WILL SURGE NWD ACROSS
CNTRL/ERN TX OVER THE NEXT SEVERAL HOURS WHICH SHOULD RESULT IN
STRONG/SEVERE THUNDERSTORM DEVELOPMENT BETWEEN 09-12Z. THIS
ACTIVITY SHOULD SPREAD RAPIDLY NEWD AHEAD OF COLD FRONT INTO THE
LOWER MS VALLEY BY 18Z. BY EARLY AFTERNOON IT APPEARS SIGNIFICANT
BOUNDARY LAYER MOISTENING/HEATING WILL HAVE OCCURRED FROM NRN
LA/SERN AR INTO WRN TN. FORECAST SOUNDINGS SUGGEST THIS REGION WILL
BECOME QUITE SUPPORTIVE FOR STRONG SUPERCELL DEVELOPMENT AS SHEAR
INCREASES ALONG WITH STEEPENING LAPSE RATES. ANY STORMS THAT EVOLVE
AHEAD OF DEEPENING LOW WITHIN EXIT REGION OF UPPER JET WILL EASILY
ROTATE AND IF 60F+ SFC DEW POINTS DO INDEED SPREAD INTO THIS REGION
THEN TORNADOES CAN BE EXPECTED...SOME POTENTIALLY STRONG AND LONG
TRACK. BETWEEN 18-00Z IT APPEARS THE GREATEST THREAT FOR TORNADIC
SUPERCELLS WILL BE ACROSS NRN LA/SERN AR/MS INTO WRN AL/TN. DURING
THE EVENING/OVERNIGHT HOURS...A CONCENTRATED ZONE OF SEVERE SHOULD
SPREAD DOWNSTREAM AS LLJ LIFTS INTO THE OH VALLEY AND SFC LOW EJECTS
INTO SRN IND.

FARTHER SOUTHEAST...WEAK WARM FRONT WILL LIKELY REMAIN ANCHORED
ACROSS SRN GA INTO SRN AL AS PERSISTENT CONVECTION DUE TO WARM
ADVECTION MAINTAINS ELY COMPONENT AND COOLER BOUNDARY LAYER
TEMPERATURES JUST SOUTH OF THE HIGHER TERRAIN. MARITIME TROPICAL
AIRMASS IS SITUATED JUST SOUTH OF THIS BOUNDARY WITH 70F+ DEW POINTS
LOCATED ACROSS THE FL PANHANDLE. THIS MOISTURE SHOULD CREEP NWWD
INTO SRN AL PRIOR TO INFLUENCE OF UPPER TROUGH. EVEN SO...MID-HIGH
LEVEL FLOW WITHIN SRN STREAM WILL INCREASE WITH TIME AND SHEAR
PROFILES WILL BECOME QUITE STRONG ATOP AN INCREASINGLY UNSTABLE
AIRMASS. IN FACT EMBEDDED IMPULSES WITHIN THIS FLOW MAY ACTIVATE
ROBUST THUNDERSTORM DEVELOPMENT EARLY IN THE PERIOD. FORECAST
SOUNDINGS ACROSS THIS REGION ARE IMPRESSIVE WITH SHEAR/INSTABILITY
STRONGLY INDICATIVE OF SUPERCELLS CAPABLE OF GENERATING
TORNADOES...SOME OF WHICH MAY BE STRONG. IT/S NOT ENTIRELY CLEAR
HOW MUCH DESTABILIZATION WILL OCCUR FARTHER NORTH INTO NRN GA/SC
WHERE CLOUDS/PRECIPITATION WILL LIMIT HEATING. DURING THE OVERNIGHT
HOURS DESTABILIZATION IS POSSIBLE ALONG THE CAROLINA COAST. IF
SUFFICIENT INSTABILITY CAN SPREAD INLAND THEN A RISK OF SEVERE
SUPERCELLS/TORNADOES CAN BE EXPECTED...PRIMARY AFTER MIDNIGHT.

..DARROW/JEWELL.. 04/02/2009

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