DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 221647
SWODY2
SPC AC 221645

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1045 AM CST TUE JAN 22 2013

VALID 231200Z - 241200Z

...NO TSTM AREAS FORECAST...

...NRN/CNTRL PLAINS THRU THE ATLANTIC SEABOARD...
THE MAIN PORTION OF A BROAD POLAR VORTEX IS NOW IN THE PROCESS OF
SHIFTING ACROSS QUEBEC TOWARD THE CANADIAN MARITIMES. BUT ANOTHER
SIGNIFICANT IMPULSE ROTATING AROUND ITS PERIPHERY IS FORECAST TO DIG
ACROSS THE GREAT LAKES AND UPPER OHIO VALLEY INTO THE NORTHERN MID
ATLANTIC COAST STATES DURING THIS FORECAST PERIOD. THIS APPEARS
LIKELY TO MAINTAIN CONFLUENT/CYCLONIC MID-LEVEL FLOW EAST OF THE
ROCKIES...WITH A SIGNIFICANT REINFORCING SURFACE COLD INTRUSION
NOSING ACROSS THE CENTRAL CANADIAN/U.S. BORDER THROUGH THE UPPER
HALF OF THE MISSISSIPPI VALLEY AND ADJACENT PLAINS/GREAT LAKES AND
OHIO VALLEY.

...PACIFIC COAST THRU ROCKIES/SRN PLAINS AND WRN GULF COAST...
AT THE SAME TIME...AS THE CENTER OF A WEAKENING PRECEDING SURFACE
RIDGE SHIFTS SOUTHWARD INTO THE NORTHEASTERN GULF OF MEXICO...SOME
INCREASE IN MOISTURE IS POSSIBLE WITH A WEAK SOUTHERLY RETURN FLOW
OFF THE WESTERN GULF OF MEXICO THROUGH EASTERN TEXAS AND THE
ARKLATEX. HOWEVER...THIS WILL OCCUR MOSTLY BENEATH A WARMING
ENVIRONMENT ON THE NORTHEASTERN PERIPHERY OF UPPER RIDGING...
DOWNSTREAM OF SUBTROPICAL EASTERN PACIFIC UPPER LOW CENTER... WITHIN
THE SOUTHERN BRANCH OF A SPLIT FLOW.

WITHIN THE NORTHERN BRANCH OF THIS LATTER REGIME...A VIGOROUS SHORT
WAVE TROUGH IS EXPECTED TO CONTINUE FLATTENING UPPER RIDGING WHILE
BEING FORCED INLAND ACROSS THE PACIFIC NORTHWEST AND NORTHERN
INTERMOUNTAIN REGION. MODELS SUGGEST THAT A PERIOD OF STRONG MID
TROPOSPHERIC COLD ADVECTION MAY ACCOMPANY THIS FEATURE...BUT
COINCIDENT WITH ONLY A WEAK TO MODEST ONSHORE FLOW...AND MOSTLY IN
THE WAKE OF EXTENSIVE EARLY DAY CLOUD COVER AND PRECIPITATION
ASSOCIATED WITH LOW-LEVEL WARM ADVECTION. WHILE WEAK
DESTABILIZATION DOES NOT APPEAR OUT OF THE QUESTION NEAR IMMEDIATE
WASHINGTON/OREGON COASTAL AREAS WEDNESDAY AFTERNOON...WITH PERHAPS
SOME POTENTIAL FOR CONVECTION CAPABLE OF PRODUCING
LIGHTNING...PROBABILITIES FOR THUNDERSTORMS STILL APPEAR BELOW 10
PERCENT AT THE PRESENT TIME.

..KERR.. 01/22/2013

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