Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
SPC AC 201244
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0644 AM CST SUN DEC 20 2015
VALID 201300Z - 211200Z
...NO SVR TSTM AREAS FORECAST...
...SUMMARY...
A FEW SMALL AREAS OF EVENING AND OVERNIGHT THUNDERSTORMS ARE
POSSIBLE WITHIN A BROAD SWATH FROM SOUTH AND EAST TEXAS TO EASTERN
KANSAS...MISSOURI AND IOWA. A FEW THUNDERSTORMS ALSO MAY OCCUR OVER
PARTS OF THE COASTAL PACIFIC NORTHWEST TODAY. IN EITHER
AREA...SEVERE-THUNDERSTORM POTENTIAL IS TOO MINIMAL FOR AN OUTLOOK.
...SYNOPSIS...
IN MID/UPPER LEVELS...SYNOPTIC-SCALE RIDGING NOW OVER MS VALLEY
REGION IS EXPECTED TO SHIFT EWD ACROSS E COAST THROUGH PERIOD...AS
BROAD REGION OF CYCLONIC FLOW BOTH TRANSLATES AND EXPANDS EWD FROM
WRN THROUGH CENTRAL CONUS. IN LATER REGIME...EMBEDDED SHORTWAVE
TROUGH IS EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER WRN AZ. THIS
PERTURBATION IS FCST TO MOVE RAPIDLY EWD ACROSS SRN ROCKIES BY 00Z.
THIS PERTURBATION THEN SHOULD TURN ENEWD WITHIN THAT EXPANSIVE
CYCLONIC-FLOW ZONE...WHILE LOSING SOME AMPLITUDE...EJECTING NEWD TO
SRN IA AND MO BY 12Z. UPSTREAM...MINOR PERTURBATION NOW ABOUT 500
NM OFFSHORE CAPE MENDOCINO IS FCST TO UNDERGO GRADUAL AMPLIFICATION
AS IT TRACKS SEWD TO SRN CA BY 00Z...THEN EWD TO NM AROUND END OF
PERIOD.
AT SFC...WEAK LOW ANALYZED AT 11Z OVER ERN SD IS FCST TO MIGRATE
NEWD TO ERN MN/WRN WI AREA BY 00Z...WITH TRAILING COLD FRONT ACROSS
SRN MN...WRN IA...SERN NEB...CENTRAL KS...THROUGH SECONDARY LOW
DEVELOPING OVER WRN KS...TO ERN CO. LEE TROUGH WILL EXTEND FROM LOW
SSWWD ACROSS TX SOUGH PLAINS AND PERMIAN BASIN REGION...WITH
DEVELOPING DRYLINE TO ITS E OVER WRN OK AND W-CENTRAL TX. BY END OF
PERIOD...SWRN LOW SHOULD MOVE NEWD TO ERN IA AND BECOME PRIMARY
CYCLONE...ASSOCIATED WITH PROXIMAL MID/UPPER-LEVEL SHORTWAVE TROUGH.
COLD FRONT SHOULD EXTEND FROM THAT LOW SWWD ACROSS NRN/WRN MO AND
SWRN OK.
...CENTRAL/E TX TO IA...
ISOLATED TO WIDELY SCATTERED TSTMS IN CLUSTERS OR SMALL BANDS ARE
POSSIBLE WITHIN THIS SWATH OVERNIGHT. COVERAGE IS EXPECTED TO BE
VERY UNEVENLY DISTRIBUTED WITHIN THIS SWATH...AND THERE MAY BE SOME
FAIRLY LARGE GAPS WITHOUT THUNDER. HOWEVER...LATEST OPERATIONAL AND
HIGH-RES/CONVECTION-ALLOWING GUIDANCE...WHILE CONSISTENTLY
GENERATING DEEP CONVECTION SOMEWHERE WITHIN EACH OF TWO REGIMES
DISCUSSED BELOW....IS NOT CONSISTENT ENOUGH IN LOCATING MINIMA TO
JUSTIFY ANY CATEGORICAL GAPS ATTM. THE MAIN PROCESSES SUPPORTING
THIS EPISODIC/STREAKY CONVECTION WILL BE...
1. WAA PLUME COVERING ALMOST THE ENTIRE SWATH OF THIS OUTLOOK.
THOUGH LARGE-SCALE SUPPORT IN MID/UPPER LEVELS WILL BE STRONGEST
OVER KS/MO/IA...GREATEST MOISTURE AND DEEPEST BUOYANCY WILL BE FROM
ARKLATEX REGION AND ERN OK SWD...IN ASSOCIATION WITH LARGEST AMOUNT
OF LOW-LEVEL MOISTURE. THOUGH LAPSE RATES WILL BE ONLY SLIGHTLY
ABOVE MOIST-ADIABATIC FROM ERN OK/WRN AR SWD...200-500 J/KG MUCAPE
SHOULD EXTEND INTO FAVORABLE ICING LAYERS FOR LTG RISK WITH ANY
CONVECTION THAT OCCURS. MAIN LOW-LEVEL LIFT MECHANISM SUPPORTING
CONVECTION WILL BE ISENTROPIC ASCENT TO LFC...INDICATING TSTM
POTENTIAL WILL BE GRADUAL IN NATURE.
2. STG LARGE-SCALE LIFT/DESTABILIZATION ALOFT...ACCOMPANYING ZONE OF
DCVA THAT IMMEDIATELY PRECEDES COMPACT SHORTWAVE TROUGH. THIS
REGIME WILL STREAK ENEWD FROM CENTRAL HIGH PLAINS ACROSS KS AND
PORTIONS MO/IA...CURRENTLY EXPECTED TO ENCOUNTER AT LEAST MRGL
MOISTURE IN WRN FRINGE OF WAA PLUME SOMEWHERE OVER CENTRAL/ERN KS.
THOUGH THAT MOISTURE WILL BE LESS THAN FARTHER S...AND ELEVATED
BUOYANCY SHALLOWER...STEEPER MIDLEVEL LAPSE RATES STILL MAY SUPPORT
DEVELOPMENT OF 200-500 J/KG MUCAPE. MOST INTENSE CELLS MAY OFFER
SMALL HAIL...BUT INFLOW-LAYER MOISTURE SUPPLY SHOULD BE TOO LIMITED
TO SUPPORT LARGE-HAIL GROWTH.
...COASTAL PAC NW...
WELL-DEFINED SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE-CHANNEL
IMAGERY OFFSHORE SWRN BC AND WA -- IS FCST TO MOVE EWD TO ESEWD
TODAY AND ONSHORE WA/NERN ORE. AS THIS OCCURS...ASSOCIATED
LARGE-SCALE DCVA/COOLING ALOFT WILL OVER SPREAD MARINE LAYER AND
YIELD SUFFICIENTLY STEEP LAPSE RATES TO SUPPORT SHALLOW BUT STILL
GLACIATED CONVECTIVE TURRETS. ISOLATED LTG IS POSSIBLE FROM THAT
CONVECTION.
..EDWARDS/COOK.. 12/20/2015
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