Post by Harleygirl on Oct 22, 2007 6:52:13 GMT -6
Forecast Discussion
SPC AC 221239
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0739 AM CDT MON OCT 22 2007
VALID 221300Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OF THE CENTRAL GULF
COAST STATES...
...CENTRAL GULF COAST STATES...
REGION WILL CONTINUE TO BE DOMINATED BY STRONG LONGWAVE TROUGH NOW
PROGRESSING ACROSS THE GREAT PLAINS. PRIMARY ENERGY WITHIN THE
BROADER TROUGH WAS EVIDENT OVER THE SRN HIGH PLAINS THIS MORNING AND
SHOULD CLOSE OFF AN UPPER LOW OVER TX DURING THE LATTER HALF OF THE
PERIOD. IN ADVANCE OF THIS SYSTEM...SLY LOW LEVEL JET WILL REMAIN
PRONOUNCED FROM SERN LA INTO THE TN/OH RIVER VALLEYS THROUGH THE
PERIOD. THIS STRENGTHENING SLY LOW LEVEL FLOW HAS ALLOWED MARITIME
TROPICAL AIR MASS TO OVERSPREAD THE CENTRAL GULF COAST WITH PW/S NOW
IN EXCESS OF 2 INCHES OVER SERN LA INTO SRN AND CENTRAL AL/MS...WITH
SURFACE DEW POINTS IN THE LOWER 70S. COMBINATION OF PERSISTENT AND
STRONG SLY FLOW ATOP A VERY MOIST BOUNDARY LAYER WILL MAINTAIN A
RISK OF LOW LEVEL ROTATION AND POSSIBLY BRIEF TORNADOES FOR MUCH OF
THE PERIOD...ESPECIALLY NEARER TO THE GULF WHERE SURFACE THETA-E
WILL BE GREATER. MODIFICATION OF LCH/S 12Z SOUNDING INDICATES
CAPPING TO SURFACE-BASED PARCELS WILL ERODE WITH TEMPERATURES IN THE
UPPER 70S...WHICH ARE CURRENTLY FORECAST TODAY.
AREAL EXTENT AND OVERALL DEGREE OF ANY ENSUING SEVERE THREAT REMAIN
UNCERTAIN AT THIS TIME GIVEN THE NEAR MOIST ADIABATIC THERMODYNAMIC
PROFILES OBSERVED AND FORECAST TO PERSIST THROUGH THE PERIOD. IT
WOULD APPEAR INCREASING PRESSURE FALLS INVOF SURFACE LOW MOVING INTO
THE LOWER MS RIVER VALLEY TODAY...AND INCREASING SSWLY MID/UPPER
LEVEL FLOW...SHOULD INCREASE RISK OF MORE ORGANIZED STORMS DURING
THE PERIOD. OF COURSE...THIS WILL BE PREDICATED ON DEVELOPMENT OF
AT LEAST MARGINAL INSTABILITY. PRIMARY SEVERE THREAT ACROSS THE
REGION WILL BE ISOLATED TORNADOES...ALTHOUGH STRONG WIND GUSTS MAY
ALSO DEVELOP WITH MORE ORGANIZED LINES/CELLS.
...TX COAST...
SURFACE COLD FRONT IS MAKING RAPID SEWD PROGRESS INTO THE TX COASTAL
PLAIN THIS MORNING AND SHOULD MOVE OFF THE MIDDLE TX COAST DURING
THE MID MORNING AND OFF THE UPPER TX AND DEEP SOUTH TX COAST BY
EARLY THIS AFTERNOON. A FEW STRONGER OR MORE ORGANIZED UPDRAFTS
SHOULD DEVELOP AHEAD OF AND JUST BEHIND THE FRONT THIS MORNING GIVEN
MARGINAL INSTABILITY MODEST DEEP LAYER SHEAR.
..EVANS.. 10/22/2007
SPC AC 221239
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0739 AM CDT MON OCT 22 2007
VALID 221300Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OF THE CENTRAL GULF
COAST STATES...
...CENTRAL GULF COAST STATES...
REGION WILL CONTINUE TO BE DOMINATED BY STRONG LONGWAVE TROUGH NOW
PROGRESSING ACROSS THE GREAT PLAINS. PRIMARY ENERGY WITHIN THE
BROADER TROUGH WAS EVIDENT OVER THE SRN HIGH PLAINS THIS MORNING AND
SHOULD CLOSE OFF AN UPPER LOW OVER TX DURING THE LATTER HALF OF THE
PERIOD. IN ADVANCE OF THIS SYSTEM...SLY LOW LEVEL JET WILL REMAIN
PRONOUNCED FROM SERN LA INTO THE TN/OH RIVER VALLEYS THROUGH THE
PERIOD. THIS STRENGTHENING SLY LOW LEVEL FLOW HAS ALLOWED MARITIME
TROPICAL AIR MASS TO OVERSPREAD THE CENTRAL GULF COAST WITH PW/S NOW
IN EXCESS OF 2 INCHES OVER SERN LA INTO SRN AND CENTRAL AL/MS...WITH
SURFACE DEW POINTS IN THE LOWER 70S. COMBINATION OF PERSISTENT AND
STRONG SLY FLOW ATOP A VERY MOIST BOUNDARY LAYER WILL MAINTAIN A
RISK OF LOW LEVEL ROTATION AND POSSIBLY BRIEF TORNADOES FOR MUCH OF
THE PERIOD...ESPECIALLY NEARER TO THE GULF WHERE SURFACE THETA-E
WILL BE GREATER. MODIFICATION OF LCH/S 12Z SOUNDING INDICATES
CAPPING TO SURFACE-BASED PARCELS WILL ERODE WITH TEMPERATURES IN THE
UPPER 70S...WHICH ARE CURRENTLY FORECAST TODAY.
AREAL EXTENT AND OVERALL DEGREE OF ANY ENSUING SEVERE THREAT REMAIN
UNCERTAIN AT THIS TIME GIVEN THE NEAR MOIST ADIABATIC THERMODYNAMIC
PROFILES OBSERVED AND FORECAST TO PERSIST THROUGH THE PERIOD. IT
WOULD APPEAR INCREASING PRESSURE FALLS INVOF SURFACE LOW MOVING INTO
THE LOWER MS RIVER VALLEY TODAY...AND INCREASING SSWLY MID/UPPER
LEVEL FLOW...SHOULD INCREASE RISK OF MORE ORGANIZED STORMS DURING
THE PERIOD. OF COURSE...THIS WILL BE PREDICATED ON DEVELOPMENT OF
AT LEAST MARGINAL INSTABILITY. PRIMARY SEVERE THREAT ACROSS THE
REGION WILL BE ISOLATED TORNADOES...ALTHOUGH STRONG WIND GUSTS MAY
ALSO DEVELOP WITH MORE ORGANIZED LINES/CELLS.
...TX COAST...
SURFACE COLD FRONT IS MAKING RAPID SEWD PROGRESS INTO THE TX COASTAL
PLAIN THIS MORNING AND SHOULD MOVE OFF THE MIDDLE TX COAST DURING
THE MID MORNING AND OFF THE UPPER TX AND DEEP SOUTH TX COAST BY
EARLY THIS AFTERNOON. A FEW STRONGER OR MORE ORGANIZED UPDRAFTS
SHOULD DEVELOP AHEAD OF AND JUST BEHIND THE FRONT THIS MORNING GIVEN
MARGINAL INSTABILITY MODEST DEEP LAYER SHEAR.
..EVANS.. 10/22/2007