Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS03 KWNS 290819
SWODY3
SPC AC 290818

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0218 AM CST MON DEC 29 2014

VALID 311200Z - 011200Z

...NO TSTM AREAS FORECAST...

...SUMMARY...
THUNDERSTORMS SHOULD NOT DEVELOP OVER THE CONTINENTAL U.S. THROUGH
NEW YEAR`S EVE...AND INTO THE FIRST SEVERAL HOURS OF 2015.  WHILE
ISOLATED THUNDER CANNOT BE RULED OUT OVER SOUTH AND EAST TEXAS OR
LOUISIANA TOWARD DAYBREAK NEW YEAR`S DAY...POTENTIAL LOOKS TOO LOW
AT THIS TIME FOR AN OUTLOOK AREA.

...SYNOPSIS...
IN MID-UPPER LEVELS...SPLIT-FLOW PATTERN WILL CONTINUE.  DOMINANT
FEATURES ALOFT WILL BE SYNOPTIC-SCALE CYCLONIC-FLOW REGIME OVER ERN
CANADA AND GREAT LAKES...WITH SEVERAL EMBEDDED SHORTWAVES...AND VERY
PRONOUNCED CYCLONE OVER WRN CONUS.  500-MB LOW ASSOCIATED WITH
LATTER FEATURE SHOULD PIVOT EWD OUT OF SERN CA AND ACROSS NRN
AZ...ONLY LOOSELY CONNECTED TO PREVAILING WLYS THROUGH TROUGH/COL
AREA OVER WY.  THOUGH MESOSCALE DIFFERENCES APPEAR AS LATE AS LAST
SEVERAL HOURS OF DAY 2 ON SPECIFIC LOW POSITION AND PHASE
SPEED...OVERALL GEOMETRY AND DIRECTIONAL TRACK OF THIS FEATURE ARE
STILL FAIRLY CONSOLIDATED AMONGST OPERATIONAL PROGS AND ALL BUT A
FEW SREF MEMBERS THROUGH PERIOD.

AT SFC...VERY LARGE/COLD ANTICYCLONE WILL COVER MOST OF CONUS E OF
ROCKIES THIS PERIOD...YIELDING STABLE/LOW-THETAE BOUNDARY LAYER
UNSUPPORTIVE OF DEEP MOIST CONVECTION.  HOWEVER...ASSOCIATED SFC
HIGH WILL WEAKEN WITH TIME STARTING LATE DAY 2 AND THROUGH DAY
3...WITH MSL PRESSURES FALLING FROM UPPER 1040S MB AROUND START OF
PERIOD OVER CENTRAL HIGH PLAINS TO LOWER 1030S BY 1/12Z.
MEANWHILE...COLD AIR MASS WILL BE OVERLAID BY STRENGTHENING
LOW-LEVEL WAA AND EARLY-STAGE/ELEVATED MOISTURE TRANSPORT ACROSS ERN
GULF STATES.

...S TX TO WRN/NRN LA...
MOIST CONVECTION INCLUDING SCATTERED SHOWERS MAY DEVELOP IN
ELEVATED...WSW-ENE-ORIENTED...LOW-LEVEL WAA REGIME DURING OVERNIGHT
HOURS OF PERIOD...SOMEWHERE WITHIN CORRIDOR 200-300 NM WIDE ROUGHLY
FROM LRD-MLU.  PROGS DIFFER CONSIDERABLY ON TIMING OF TSTM ONSET
WITHIN THIS REGIME...WITH MAJORITY SUGGESTING AFTER 01/12Z.
HOWEVER...01/09Z-01/12Z FCST SOUNDINGS FROM TYPICALLY
AGGRESSIVE/HIGHER-THETAE NAM RETURN-FLOW REGIME SUGGEST ENOUGH
THETAE IN 800-850-MB LAYER TO CREATE UP TO 300 J/KG MUCAPE...SLIVER
OF WHICH EXTENDS THROUGH WEAK MID-UPPER-LEVEL LAPSE RATES INTO ICING
LAYERS SUITABLE FOR LTG.

AS SUCH...A FEW LTG STRIKES CANNOT BE RULED OUT ENTIRELY BEFORE 12Z.
 HOWEVER...AT THIS EARLY JUNCTURE...THUNDER POTENTIAL FOR LAST FEW
HOURS OF DAY-3 PERIOD LOOKS TOO UNCERTAIN AND CONDITIONAL...IN BOTH
GEOGRAPHY AND TIME...FOR CATEGORICAL/10% TSTM AREA.

..EDWARDS.. 12/29/2014




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