Schweizer Sturmforum

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0148 PM CST SUN FEB 08 2009

VALID 082000Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN HIGH
PLAINS...

...SRN HIGH PLAINS...
WATER VAPOR IMAGERY CURRENTLY SHOWS A LARGE NEGATIVELY-TILTED
UPPER-LEVEL TROUGH FROM THE DESERT SOUTHWEST ORIENTED SSEWD ALONG
THE GULF OF CALIFORNIA. THIS SYSTEM IS FORECAST TO MOVE QUICKLY
ENEWD ACROSS THE FOUR CORNERS REGION AND NRN MEXICO TODAY. AHEAD OF
THE TROUGH...RUC ANALYSIS SHOWS THE LEADING EDGE OF STRONG
LARGE-SCALE ASCENT LOCATED JUST WEST OF EL PASO ON THE NRN END OF A
WELL-DEVELOPED DRY SLOT. THIS ZONE OF STRONG ASCENT ASSOCIATED WITH
A NARROW BAND OF MID-LEVEL MOISTURE WILL MOVE ENEWD INTO ERN NM BY
LATE THIS AFTERNOON WHERE RUC ANALYSIS SUGGESTS LOW-LEVEL
CONVERGENCE IS INCREASING. CONVECTION APPEARS LIKELY TO FIRST
INITIATE ALONG THIS BAND OF ASCENT IN NERN NM WITH CONVECTION
QUICKLY EXPANDING SWD ACROSS FAR ERN NM INTO THE PECOS RIVER VALLEY
BY EARLY TO MID EVENING. THE LINE OF CONVECTION WILL LIKELY
INTENSIFY...MOVING EWD ACROSS WEST TX DURING THE LATE EVENING AND
OVERNIGHT PERIOD.

CONCERNING THE SEVERE POTENTIAL...SEVERAL FACTORS ARE COMING
TOGETHER ACROSS ERN NM AND WEST TX FOR THE POTENTIAL FOR SEVERE
STORMS. 1) THE RUC IS CURRENTLY ANALYZING A POCKET OF INSTABILITY
OVER SE NM WHERE SBCAPE VALUES RANGE FROM 250 TO 500 J/KG. THIS
INSTABILITY SHOULD GRADUALLY INCREASE AND MAY EXPAND EWD INTO PARTS
OF WEST TX THROUGH THE LATE AFTERNOON. 2) THE RUC SHOWS STRONG
VERTICAL SHEAR /0-6 KM SHEAR OF 50 TO 70 KT/ OVER THE WRN HALF OF
THE SLIGHT RISK AREA. 3) A 40 TO 50 KT LOW-LEVEL JET IS ANALYZED
OVER WCNTRL TX. THIS FEATURE WILL EXPAND NNWWD STRENGTHENING TO
ABOUT 60 KT THIS EVENING. AS THE STRONG ASCENT COMES OUT INTO THE
HIGH PLAINS...THE INSTABILITY...VERTICAL SHEAR AND STRONG LOW-LEVEL
FLOW SHOULD SUPPORT A POTENTIAL FOR SEVERE THUNDERSTORMS. ALTHOUGH
THE CONVECTION SHOULD BE ORIENTED IN A GENERAL LINE FROM NORTH TO
SOUTH ACROSS WEST TX...SMALLER SCALE LINE-SEGMENTS SHOULD BE CAPABLE
OF PRODUCING ISOLATED DAMAGING WIND GUSTS. THE HAIL THREAT SHOULD BE
MORE CONFINED TO A NARROW CORRIDOR ALONG THE NM-TX STATE-LINE WHERE
MID-LEVEL LAPSE RATES ARE FORECAST TO BE STEEPER AND TEMPS WILL BE
COLD ALOFT NEAR THE APPROACHING UPPER-LEVEL TROUGH. IF A VIGOROUS
SQUALL-LINE CAN CONTINUE OVERNIGHT IN SPITE OF WEAK
INSTABILITY...THEN THE WIND DAMAGE THREAT COULD EXTEND AS FAR EAST
AS WRN OK LATE IN THE PERIOD.

..BROYLES.. 02/08/2009

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1208 AM CST TUE FEB 10 2009

VALID 101200Z - 111200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS ERN OK...NORTH CENTRAL
AND NERN TX...NWRN LA...AND MUCH OF AR FOR LATE THIS AFTERNOON INTO
TUESDAY NIGHT...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
FROM EAST TX/LA NWD TO LOWER MO/MID MS VALLEYS...

...SIGNIFICANT SEVERE WEATHER OUTBREAK INCLUDING TORNADOES AND
DAMAGING WINDS IS EXPECTED TO DEVELOP LATE THIS AFTERNOON AND
PERSIST INTO TUESDAY NIGHT ACROSS THE ERN HALF OF OK...NORTH
CENTRAL-NERN TX INTO NWRN LA AND MUCH OF AR...

...SYNOPSIS...
STRONG UPPER TROUGH...CURRENTLY MOVING THROUGH THE LOWER CO RIVER
VALLEY WITH AN ACCOMPANYING 95 KT MID LEVEL JET MAX...WILL TRANSLATE
EWD REACHING THE SRN HIGH PLAINS BY 00Z. THIS TROUGH WILL THEN
BECOME NEGATIVELY TILTED AND DEEPEN TUESDAY NIGHT AS IT TRACKS ENEWD
TOWARD ERN KS/ERN OK. MODELS SUGGEST A SMALL CLOSED LOW SHOULD
DEVELOP OVER SERN KS/ERN OK BY 12Z WEDNESDAY. A 90+ KT MID LEVEL
JET WILL SPREAD EWD ACROSS NRN TX AND OK TUESDAY NIGHT...WITH THE
STRONGEST CORE OF MID LEVEL WINDS /110 KT/ EXPECTED TO SPREAD ACROSS
NRN TX TO THE ARKLATEX BY 12Z WEDNESDAY.

WHILE MODELS TEND TO AGREE WITH THE TRACK OF THE UPPER TROUGH...THEY
DIFFER WITH THE TRACK OF THE PRIMARY SURFACE LOW. THE NAM IS THE
FARTHEST NORTH TAKING THE LOW ACROSS KS INTO CENTRAL MO THIS
FORECAST PERIOD...WHILE THE GFS SUGGESTS THE SURFACE LOW WILL TRACK
ENEWD ACROSS CENTRAL/NRN OK INTO SRN MO BY 12Z WEDNESDAY. A FAIRLY
LARGE WARM SECTOR SHOULD DEVELOP TODAY... EXTENDING NWD THROUGH ERN
KS AND MUCH OF MO AS SLY LOW LEVEL WINDS TRANSPORT MOISTURE NWD...
WITH A WARM FRONT POSSIBLY REACHING NRN MO INTO CENTRAL IL. A
PACIFIC COLD FRONT ACCOMPANYING THE UPPER TROUGH WILL MOVE INTO
CENTRAL PARTS OF OK/TX BY MID-LATE AFTERNOON WHERE IT WILL MERGE
WITH A DRY LINE. THIS FRONT IS PROGGED TO SURGE EWD REACHING ERN
MO...ERN AR...AND EXTEND SWWD INTO THE NWRN GULF BY 12Z WEDNESDAY.

...SRN PLAINS/LOWER MS VALLEY NWD TO NRN MO/MID MS VALLEY...
LOW LEVEL MOISTURE RETURNING NWD ACROSS THE WARM SECTOR TODAY
BENEATH A PLUME OF STEEP MID LEVEL LAPSE RATES EMANATING NEWD FROM
THE MEXICAN PLATEAU WILL AID IN DESTABILIZATION. SURFACE DEWPOINTS
IN THE LOWER 60S ARE EXPECTED TO REACH NERN TX/SERN OK AND INTO
CENTRAL AR. ALTHOUGH CLOUDINESS WILL TEND TO LIMIT SURFACE HEATING
EAST OF THE DRY LINE...A MODERATELY UNSTABLE AIR MASS IS EXPECTED TO
DEVELOP ACROSS CENTRAL/ERN OK INTO CENTRAL/ NERN TX.

MODELS CONTINUE TO SUGGEST TSTM DEVELOPMENT WILL BE POSSIBLE BY
EARLY-MID AFTERNOON ACROSS PARTS OF ERN TX/SERN OK INTO ADJACENT
PARTS OF AR/LA. SOME SURFACE HEATING WITHIN THE MOISTURE RETURN
SHOULD PROVE SUFFICIENT FOR CONVECTION TO DEVELOP WITHIN A WEAKLY
CAPPED AIR MASS. DIFFLUENT FLOW ALOFT ACROSS THE ARKLATEX REGION BY
AFTERNOON SUGGESTS THIS EARLY ACTIVITY SHOULD BE DISCRETE... WHILE
STRENGTHENING SLY WINDS ACROSS THIS AREA INTO THE AFTERNOON WILL
RESULT IN CURVED HODOGRAPHS/TORNADO POTENTIAL.

GREATER SEVERE WEATHER THREAT IS EXPECTED TO DEVELOP ALONG THE DRY
LINE IN CENTRAL OK TO CENTRAL TX BY LATE AFTERNOON /AFTER 21Z/...
GENERALLY ALONG OR JUST EAST OF THE I-35 CORRIDOR. ADDITIONAL
STRENGTHENING OF THE SLY LLJ /50+ KT/ FROM E TX/LA TO ERN KS/MO WILL
RESULT IN LARGE CURVED HODOGRAPHS AND THE LIKELIHOOD FOR
STRONG/SIGNIFICANT TORNADOES AS STRONG UPPER FORCING WITH THE TROUGH
SPREADS INTO THE SRN PLAINS. IF CONFIDENCE BECOMES GREATER IN THE
TRACK OF THE PRIMARY SURFACE LOW...PORTIONS OF THE MODERATE RISK
AREA MAY NEED TO BE UPGRADED TO A HIGH RISK.

A SIGNIFICANT DAMAGING WIND THREAT IS FORECAST TO DEVELOP BY EARLY
TUESDAY EVENING AS THE COLD FRONT OVERTAKES THE DRY LINE...AND
STRONG WLY LOW-MID LEVEL WINDS SPREAD EWD ACROSS SRN OK/NRN TX
REACHING THE ARKLATEX REGION BY 11/09Z AND INTO NRN LA AND CENTRAL
AR LATE IN THE PERIOD.

AS THE WARM SECTOR SPREADS FARTHER N TOWARD THE LOWER MO VALLEY...
TSTM ACTIVITY DEVELOPING THIS EVENING ACROSS OK/AR WILL TRACK NEWD
WITH THERMODYNAMIC/KINEMATICS FAVORABLE FOR HAIL...STRONG WINDS AND
POSSIBLY TORNADOES EXTENDING THROUGH ERN KS AND MUCH OF MO.

..PETERS.. 02/10/2009

SUPERCELL STORM DEVELOPMENT IS EXPECTED IN THE NEXT 1-2 HOURS FROM S
CENTRAL OKLAHOMA SWWD INTO PARTS OF CENTRAL TX. RESULTING SEVERE
THREAT -- INCLUDING THE POTENTIAL FOR TORNADOES -- WILL REQUIRE
TORNADO WATCH ISSUANCE.

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...DRYLINE INITIATION OK/TX...
GIVEN LATEST MODEL GUIDANCE AND OBSERVATIONAL TRENDS...
THUNDERSTORMS ARE EXPECTED TO DEVELOP 20-22Z ALONG DRYLINE OVER
WESTERN OK AND NORTHWEST TX. THESE STORMS WILL LIKELY BE
SUPERCELLULAR WITH A RISK OF VERY LARGE HAIL AND TORNADOES. THE
STORMS WILL BECOME MORE NUMEROUS BY EARLY EVENING /AFTER DARK/ AND
TRACK NORTHEASTWARD INTO NORTHEAST TX AND EASTERN OK. MUCH STRONGER
VERTICAL SHEAR PROFILES IN THIS REGION /EFFECTIVE HELICITY OF 400+
M2/S2/ WILL ALSO INCREASE THE RISK OF STRONG TORNADOES. HAVE CHOSEN
TO MAINTAIN CATEGORICAL MODERATE RISK FOR THIS AFTERNOON DUE TO
CONTINUED CONCERNS OVER THE QUALITY OF LOW LEVEL MOISTURE...BUT AN
UPGRADE TO HIGH RISK WILL REMAIN POSSIBLE AT 20Z.
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