Monday, January 21, 2008

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 210538
SWODY1
SPC AC 210535

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1135 PM CST SUN JAN 20 2008

VALID 211200Z - 221200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
A COLD/STABLE AIRMASS WILL CONTINUE ACROSS MUCH OF THE COUNTRY EAST
OF THE ROCKIES AS 1040 MB HIGH PRESSURE SHIFTS EASTWARD ACROSS THE
OHIO VALLEY/MID ATLANTIC STATES TODAY. UPPER FLOW PATTERN WILL BE
HIGHLIGHTED BY AN UPPER TROUGH TRANSITIONING SOUTHEASTWARD ACROSS
EAST CENTRAL CANADA AND THE UPPER MIDWEST...WHILE THE WESTERN STATES
UPPER LOW BEGINS TO CUT-OFF/RETROGRADE WESTWARD OFF THE NORTHERN CA
COAST. MEANWHILE...THE SOUTHERN TIER OF STATES WILL BE DOMINATED BY
A MODERATELY STRONG LOW AMPLITUDE BELT OF WESTERLY UPPER FLOW.

..EAST TX TO LA/SOUTHERN AR...
AS A WEAK WARM FRONT/INVERTED TROUGH DEVELOPS NORTHWARD ACROSS EAST
TX THROUGH THE DAY...SCATTERED/MAINLY ELEVATED THUNDERSTORMS WILL
BECOME INCREASINGLY POSSIBLE LATE THIS AFTERNOON INTO TONIGHT FROM
EAST CENTRAL TX/TX COASTAL PLAIN INTO PORTIONS OF LA/AR. WHILE
STRONG/VEERING FLOW THROUGH THE LOW TO MID TROPOSPHERE WOULD FAVOR
THE CONDITIONAL POSSIBILITY OF A FEW SEVERE STORMS ACROSS EAST TX
THIS AFTERNOON/EVENING...ONLY A MODEST INFLUX OF MODIFIED GULF
MOISTURE /UPPER 50S F/ AND WIDESPREAD CLOUD COVER/MARGINAL
INSTABILITY WILL LIKELY PRECLUDE A SEVERE RISK. NAM-KF CONTROL
FORECAST SOUNDINGS SUGGEST LITTLE POTENTIAL FOR SURFACE BASED
STORMS...WITH SURFACE BASED INHIBITION LARGELY OWING TO THE
WIDESPREAD CLOUD COVER/MARGINAL BOUNDARY LAYER MOISTURE AND A WARM
CAPPING LAYER ABOVE 850 MB.

..NORTHERN CA...
UPPER LOW IS FORECAST TO SHIFT SOUTHWESTWARD OFF THE NORTHERN CA
COAST THROUGH THE PERIOD. WITH COLD MID LEVEL TEMPERATURES /AROUND
-30 C AT 500 MB/...A STEEP LAPSE RATE ENVIRONMENT MAY PROMOTE A FEW
LOW-TOPPED THUNDERSTORMS/ISOLATED LIGHTNING STRIKES ALONG THE
NORTHERN CA COAST THIS AFTERNOON/EVENING.

..SOUTHERN FL PENINSULA...
A MOIST/MARGINALLY UNSTABLE AIRMASS MAY PROMOTE SUFFICIENTLY DEEP
UPDRAFTS FOR ISOLATED LIGHTNING STRIKES THIS
AFTERNOON/TONIGHT...MOST LIKELY ALONG THE SOUTHEAST FL COAST AND
ADJACENT COASTAL WATERS.

.GUYER.. 01/21/2008

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