SWODY2
SPC AC 070539
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1139 PM CST FRI FEB 06 2009
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE SUN/SUN NIGHT ACROSS PARTS
OF THE SRN HIGH PLAINS....
...SYNOPSIS...
A COUPLE OF DISTINCT BELTS OF STRONGER POLAR WESTERLIES ARE EXPECTED
TO PERSIST ACROSS THE U.S. THROUGH THIS FORECAST PERIOD AND BEYOND.
AND...MODELS INDICATE THAT THE SOUTHERN BRANCH OF THIS REGIME WILL
GRADUALLY BECOME MORE PROMINENT BY LATE IN THE WEEKEND. GUIDANCE
REMAINS VERY SIMILAR CONCERNING ASSOCIATED SHORT WAVE
DEVELOPMENTS...PARTICULARLY WITH A LEAD IMPULSE ALREADY BEGINNING TO
DIG INTO THE SOUTHWESTERN U.S. AND NORTHWEST MEXICO. BY
SUNDAY...THIS FEATURE IS PROGGED TO ACCELERATE OUT OF THE PLATEAU
REGION...AS ANOTHER STRONGER UPSTREAM SHORT WAVE TROUGH DIGS TOWARD
THE CALIFORNIA COAST. THIS IS EXPECTED TO SUPPORT STRONG SURFACE
CYCLOGENESIS TO THE LEE OF THE CENTRAL ROCKIES LATE SUNDAY/SUNDAY
NIGHT...ACCOMPANIED BY THE DEVELOPMENT OF A 50-70 KT SOUTHERLY
LOW-LEVEL JET ACROSS THE CENTRAL/SOUTHERN PLAINS...AS A 90 KT 500 MB
JET STREAK PROPAGATES FROM THE NORTHERN MEXICAN PLATEAU THROUGH THE
RED RIVER VALLEY.
DESPITE AN INCREASINGLY FAVORABLE LARGE-SCALE PATTERN FOR STRONG/
SEVERE CONVECTIVE DEVELOPMENT ACROSS THE SOUTH CENTRAL U.S...A
RECENT SERIES OF COLD INTRUSIONS HAS SUBSTANTIALLY IMPACTED THE
LOW-LEVEL ENVIRONMENT OVER THE GULF OF MEXICO. ALTHOUGH A MODEST
RETURN FLOW OF MOISTURE IS ALREADY UNDERWAY OVER PARTS OF THE
WESTERN GULF INTO SOUTH/EAST TEXAS...CURRENT INDICATIONS ARE THAT
THE QUALITY OF THE LOW-LEVEL MOISTURE MAY NOT IMPROVE MUCH AS ONLY A
SLOW GULF BOUNDARY LAYER MODIFICATION PROCEEDS THROUGH LATE
SUNDAY/EARLY MONDAY. THIS WILL HAMPER DESTABILIZATION...WHILE
PROBABLY ALSO LIMITING THE OVERALL CONVECTIVE POTENTIAL.
...SOUTHERN PLAINS...
LOW CLOUDS...ASSOCIATED WITH THE MOISTURE RETURN BENEATH A DRY
CAPPING ELEVATED MIXED LAYER...ARE STILL EXPECTED TO RESTRICT
SURFACE HEATING AS FAR WEST AS THE TEXAS SOUTH PLAINS AND PANHANDLE
REGION. BUT...EVEN WITH PEAK AFTERNOON SURFACE TEMPERATURES IN THE
UPPER 50S AND DEW POINTS IN THE UPPER 40S...MID-LEVEL LAPSE RATES
ARE EXPECTED TO BE STEEP ENOUGH FOR AT LEAST WEAK BOUNDARY LAYER
BASED CAPE ACROSS THE HIGH PLAINS. NAM FORECAST SOUNDINGS WITH THE
KAIN-FRITSCH PARAMETERIZATION INDICATE CAPE AS HIGH AS 750 J/KG OR
SO...BUT SHORT RANGE ENSEMBLE GUIDANCE SUGGEST VALUES OF 250-500
J/KG ARE MORE LIKELY. EVEN SO...WITH STRONG FORCING...THERMODYNAMIC
PROFILES APPEAR FAVORABLE FOR VIGOROUS STORM DEVELOPMENT. THIS IS
EXPECTED TO OCCUR ALONG OR AHEAD OF A PACIFIC COLD FRONT ADVANCING
TO THE LEE OF THE SOUTHERN ROCKIES.
CONVECTION MAY INITIATE LATE SUNDAY AFTERNOON ACROSS EXTREME EASTERN
NEW MEXICO...WHERE EARLY STORMS MAY BE CAPABLE OF PRODUCING SOME
LARGE HAIL. BUT...A RAPIDLY DEVELOPING NARROW SQUALL LINE BY SUNDAY
EVENING IS EXPECTED TO BE ACCOMPANIED BY PRIMARILY A DAMAGING WIND
THREAT...AS IT ADVANCES INTO THE TEXAS PANHANDLE AND SOUTH
PLAINS...WHERE LOW-LEVEL HODOGRAPHS WILL BECOME INCREASINGLY LARGE
BENEATH STRONG SOUTH SOUTHWESTERLY MID/UPPER FLOW.
AS STRONGER MID-LEVEL FORCING LIFTS TOWARD THE CENTRAL PLAINS
THROUGH 12Z MONDAY...THERE IS STILL SOME QUESTION WHETHER
THUNDERSTORM ACTIVITY WILL PERSIST THROUGH THE NIGHT ACROSS OKLAHOMA
INTO NORTH CENTRAL TEXAS...DUE TO RELATIVELY WARM MID- LEVEL
TEMPERATURES...EVEN IN THE PRESENCE OF INCREASING LOW-LEVEL
MOISTURE. HOWEVER...AT LEAST LOW TOPPED CONVECTION PROBABLY WILL
CONTINUE...PERHAPS WITH A LINGERING RISK FOR STRONG GUSTY WINDS.
..KERR.. 02/07/2009
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