SPC Day 2 Thunderstorm Outlook Issued 1730Z 20040116

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ZCZC SPCSWODY2 ALL
ACUS02 KWNS 161756
SPC AC 161756

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1156 AM CST FRI JAN 16 2004

VALID 171200Z - 181200Z

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 40 E
PSX 40 S CLL 35 NNE CLL GGG 10 WNW MLU 45 SW JAN LUL 55 S SEM DHN 10
NW MAI AQQ.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 30 ESE DUG SAD TCS
GDP FST 35 SSW SJT 35 WSW MWL FSI TUL UMN 10 SSE HSV ATL MCN 45 WNW
CTY.

...THERE IS A SLGT RISK OF SVR TSTMS SATURDAY/SATURDAY NIGHT ACROSS
THE GULF COAST STATES....

SPLIT FLOW REGIME/BLOCK PERSISTS IN LARGE-SCALE PATTERN FROM THE
EASTERN PACIFIC INTO WESTERN NORTH AMERICA.  UPPER RIDGE  REMAINS
OVER THE INTERMOUNTAIN WEST...WITH BROAD TROUGH TO ITS SOUTH...
ACROSS BAJA AND THE MEXICAN PLATEAU.

ETA/AVN MODELS HAVE BEEN SIMILAR IN FORECAST PROGRESSION OF A COUPLE
OF SHORT WAVES THROUGH THIS REGIME...AND THEIR EVOLUTION INTO A
LARGER-SCALE TROUGH ACROSS THE SOUTH CENTRAL U.S. LATE TONIGHT
THROUGH SATURDAY.  ONE SHORT WAVE...NOW DIGGING ACROSS THE EASTERN
GREAT BASIN...EAST OF RIDGE AXIS...IS PROGGED TO CONTINUE SOUTHWARD
INTO THE NORTHERN MEXICAN PLATEAU BY LATE SATURDAY EVENING.  AS THIS
OCCURS...VIGOROUS SOUTHERN BRANCH SHORT WAVE IS PROGGED TO LIFT OUT
OF BAJA/MEXICAN PLATEAU UPPER TROUGH.  LATEST WATER VAPOR IMAGERY
SUGGESTS LATTER IMPULSE IS ALREADY BEGINNING TO DEVELOP EAST OF
SOUTHERN BAJA. AS THIS FEATURE...AND ASSOCIATED MID/UPPER JET
STREAK...SHIFT ACROSS THE NORTHERN MEXICAN PLATEAU EARLY
SATURDAY...LOW/MID-LEVEL CYCLONE IS FORECAST TO BRIEFLY FORM OVER
THE SOUTH CENTRAL PLAINS...BEFORE UPPER JET CONTINUES EASTWARD
ACROSS THE NORTHERN GULF OF MEXICO SATURDAY NIGHT.

IN RESPONSE TO EVOLVING UPPER FLOW PATTERN...INFLUX OF MID/HIGH
LEVEL MOISTURE OFF THE LOWER LATITUDE PACIFIC INTO THE SOUTH CENTRAL
U.S. HAS OCCURRED...IN CONJUNCTION WITH A NORTHWARD TRANSPORT OF
MOISTURE OFF THE WESTERN GULF OF MEXICO.  16/12Z SOUNDINGS INDICATE
ENVIRONMENT WITH UNSEASONABLY HIGH PRECIPITABLE WATER EXTENDING FROM
THE RIO GRANDE VALLEY INTO THE LOWER MISSOURI VALLEY...WHICH WILL
SUPPORT WIDESPREAD RAINS AND EMBEDDED CONVECTION.  THUNDERSTORM
ACTIVITY APPEARS MOST LIKELY FROM THE LOWER RIO GRANDE VALLEY INTO
THE GULF STATES...WHERE MID-LEVEL COOLING/FORCING FOR UPWARD
VERTICAL MOTION WILL BE STRONGEST IN EXIT REGION OF UPPER JET.

...EAST TEXAS...
INITIAL WAVE OF VIGOROUS CONVECTIVE DEVELOPMENT...IN STRONGER
LOW-LEVEL WARM ADVECTION REGIME AHEAD OF APPROACHING SHORT WAVE...
APPEARS LIKELY TO SHIFT OUT OF EASTERN TEXAS INTO THE LOWER
MISSISSIPPI VALLEY EARLY SATURDAY.  MODELS THEN SUGGEST PRONOUNCED
MID-LEVEL DRYING IN SLOT ACROSS DEEP SOUTH/SOUTHEAST TEXAS...WHICH
WILL CONTRIBUTE TO STRONG CONVECTIVE INSTABILITY AND ALLOW SURFACE
HEATING OF MOIST PRE-FRONTAL BOUNDARY LAYER WITH 60F+ DEW POINTS.

POINT FORECAST SOUNDINGS INDICATE CAPE MAY EXCEED 1500 J/KG ACROSS
PARTS OF SOUTHEAST TEXAS BY LATE AFTERNOON.  WHILE STRONGER
LOW-LEVEL FORCING WILL HAVE SHIFTED EASTWARD INTO THE LOWER
MISSISSIPPI VALLEY...INCREASING MID-LEVEL FORCING FOR UPWARD
VERTICAL MOTION ALONG/JUST AHEAD OF UPPER TROUGH AXIS SHIFTING
ACROSS EAST TEXAS MAY BE SUFFICIENT FOR CONVECTIVE DEVELOPMENT. 
GIVEN MAGNITUDE OF INSTABILITY... MID-LEVEL FLOW IN SOUTHEAST
QUADRANT OF CLOSED LOW WILL BE SUPPORTIVE OF SUPERCELLS ...ENHANCING
THREAT FOR LARGE HAIL/DAMAGING WIND GUSTS.  ACTIVITY WILL LIKELY
DIMINISH WITH LOSS OF SURFACE HEATING BY LATE SATURDAY
EVENING...BEFORE SPREADING INTO THE LOWER MISSISSIPPI VALLEY.

...CENTRAL/EASTERN GULF COAST AREAS...
BOUNDARY LAYER WILL BE SLOWER TO MODIFY IN WAKE OF COLD SURFACE
RIDGE. HOWEVER...BY LATE SATURDAY AFTERNOON...SURFACE DEW POINTS
ARE EXPECTED TO INCREASE INTO THE 60S ACROSS MUCH OF SOUTHEAST
LOUISIANA/PARTS OF SOUTHERN MISSISSIPPI...BENEATH 40+ KT SOUTHERLY
LOW-LEVEL JET AXIS.  WITH DEVELOPMENT OF SURFACE-BASED INSTABILITY
...POTENTIAL FOR SUPERCELLS/ISOLATED TORNADOES WILL INCREASE IN ZONE
OF STRONGER LOW-LEVEL WARM ADVECTION...ALONG EAST/WEST WARM FRONTAL
ZONE NEAR THE CENTRAL GULF COAST.  THIS THREAT WILL PERSIST...AND
MAY INCREASE OVERNIGHT ACROSS THE EASTERN GULF COASTAL AREAS...AS
STRONGER MID-LEVEL FORCING SHIFTS RAPIDLY EAST NORTHEASTWARD OUT OF
THE LOWER RIO GRANDE VALLEY.

..KERR.. 01/16/2004

...NOTICE...
FOR USERS DECODING THE POINTS PARAGRAPH HEREIN...LATITUDE AND
LONGITUDE POINTS FOR THE CATEGORICAL AND PROBABILISTIC OUTLOOK
GRAPHICS ALSO ARE LOCATED IN A SEPARATE PRODUCT UNDER THE WMO
HEADINGS WUUS01 PTSDY1...WUUS02 PTSDY2...AND WUUS03 PTSDY3.  THE
INCLUSION OF POINTS IN THIS PRODUCT WILL EVENTUALLY BE DISCONTINUED.

$$