SWODY1
SPC AC 250528
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1128 PM CST MON DEC 24 2007
VALID 251200Z - 261200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
PROGRESSIVE...POLAR WAVE TRAIN WILL CONTINUE THROUGH THE PERIOD FROM
THE CNTRL PACIFIC EWD ACROSS THE CONUS. SHORT WAVE TROUGH INITIALLY
OVER THE LOWER MS VALLEY WILL EVOLVE INTO A CLOSED LOW WHILE
TRANSLATING EWD THROUGH THE CNTRL GULF COAST STATES...AND THEN MORE
NEWD TOWARD THE SERN ATLANTIC COAST. OTHER SYSTEM OF INTEREST IS
STRONG TROUGH CENTERED NEAR 48 N/148 W AS OF 05Z. THIS FEATURE WILL
MOVE SEWD INTO THE PACIFIC NW TODAY INTO TONIGHT. IN THE LOW
LEVELS...A WEAK SURFACE WAVE DEVELOPING EWD ACROSS THE GULF COAST
STATES WILL GRADUALLY WEAKEN AS CYCLOGENESIS OCCURS OFF THE SERN
ATLANTIC COAST. THIS LOW WILL UNDERGO SLIGHT DEEPENING OVERNIGHT
WHILE DEVELOPING NEWD JUST OFF THE COAST OF THE CAROLINAS.
..CAROLINA COASTS...
RECENT TRENDS IN MODEL GUIDANCE HAVE SHOWN A SLOWER AND MORE
AMPLIFIED CHARACTER TO UPPER LOW WHICH WILL BE APPROACHING AREA LATE
TONIGHT. AS A RESULT...THE LOW-LEVEL RESPONSE IS NOW CONSIDERABLY
STRONGER...ALLOWING A MORE MOIST LOW-LEVEL AIR MASS TO MOVE NWWD
ONTO THE COAST IN ADVANCE OF DEEPENING SURFACE LOW. WHILE MIDLEVEL
LAPSE RATES ARE NOT FORECAST TO BE PARTICULARLY STEEP...THIS
INCREASE IN MOISTURE WILL SUPPORT THE DEVELOPMENT OF WEAK CONVECTIVE
INSTABILITY /MUCAPES OF 300-400 J PER KG/ TONIGHT...NAMELY FOR
PARCELS ROOTED IN THE 0.5-1.0 KM AGL LAYER.
THE MAJORITY OF TSTM ACTIVITY /AND ANY ASSOCIATED SEVERE THREAT/ IS
EXPECTED TO REMAIN TO THE RIGHT OF SURFACE LOW TRACK OVER THE GULF
STREAM. HOWEVER...A FEW ELEVATED STORMS APPEAR LIKELY ALONG THE
COAST TONIGHT INTO WEDNESDAY MORNING.
..WA/ORE COASTS...
CURRENT WATER VAPOR IMAGERY AND OCEANIC LIGHTNING DATA SUGGEST THAT
UPSTREAM SYSTEM OVER THE NERN PACIFIC IS QUITE STRONG.
INDEED...LATEST MODEL GUIDANCE INDICATES THAT CONSIDERABLE HEIGHT
FALLS/DYNAMIC COOLING WILL ACCOMPANY THIS SYSTEM ONSHORE. RESULTANT
STEEPENING OF MIDLEVEL LAPSE RATES COUPLED WITH THE MOIST...ONSHORE
FLOW IN THE POST-FRONTAL AIR MASS WILL SUPPORT WEAK AIR MASS
DESTABILIZATION...ESPECIALLY THIS AFTERNOON INTO TONIGHT. FORECAST
SOUNDINGS SUGGEST THAT EQUILIBRIUM TEMPERATURES WILL BECOME
SUFFICIENTLY COOL FOR CHARGE SEPARATION/LIGHTNING DEVELOPMENT WITH
THE DEEPER CONVECTIVE ELEMENTS MOVING ONTO THE COAST.
.MEAD.. 12/25/2007
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