DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 011946
SWODY1
SPC AC 011944

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0144 PM CST SAT DEC 01 2012

VALID 012000Z - 021200Z

...NO SVR TSTM AREAS FORECAST...

...PARTS OF ERN ID/WRN WY...
LIGHTNING DATA SHOWED A FEW TSTMS HAD DEVELOPED ACROSS THIS REGION
SINCE ABOUT 1645Z. THESE LIGHTNING STRIKES APPEAR TO BE ASSOCIATED
WITH A BAND OF FORCING FOR ASCENT...COOLER MIDLEVEL TEMPERATURES...
AND STEEPER LAPSE RATES ATTENDING A PROGRESSIVE LEAD SHORTWAVE
TROUGH. GIVEN THIS ACTIVITY IS ONGOING AND THE 15Z SREF AND 12Z
NAM/GFS SUGGEST ADDITIONAL TSTMS REMAIN POSSIBLE THROUGH ABOUT
02/00Z...A SMALL 10 PERCENT TSTM AREA HAS BEEN ADDED TO THIS
CONVECTIVE OUTLOOK.

...ELSEWHERE...
THE GENERAL TSTM AREA FORECASTS OVER THE WA/NRN ORE COASTS AND OVER
PARTS OF THE OH VALLEY AND GREAT LAKES REMAIN UNCHANGED.

..PETERS.. 12/01/2012

.PREV DISCUSSION... /ISSUED 0940 AM CST SAT DEC 01 2012/

...SYNOPSIS...

THE PERSISTENT UPPER-LEVEL VORTEX OFF THE BRITISH COLUMBIA COAST
WILL BEGIN TO BREAK DOWN THIS PERIOD IN RESPONSE TO THE DEVELOPMENT
OF A LARGER AND MORE INTENSE SYSTEM OVER THE GULF OF AK. THIS
PROCESS WILL RESULT IN THE EVOLUTION OF THE FORMER INTO AN OPEN WAVE
WHICH WILL PHASE WITH AN INTENSE VORTICITY MAXIMUM CURRENTLY NEAR
43.5N/137.5W...BOTH OF WHICH WILL REACH THE PACIFIC COAST FROM
BRITISH COLUMBIA TO NRN CA BY THE END OF THE D1 PERIOD. DOWNSTREAM
FROM THESE DEVELOPMENTS...THE LARGE-SCALE PATTERN WILL REMAIN
QUASI-ZONAL WITH A SERIES OF EMBEDDED...WEAK PERTURBATIONS
TRANSLATING ACROSS THE NRN CONUS.

IN THE LOW LEVELS...A WEAK SURFACE CYCLONE OVER THE RED RIVER VALLEY
OF ND-MN WILL DEVELOP EWD INTO THE UPPER GREAT LAKES WITH AN
ASSOCIATED COLD FRONT ADVANCING SEWD THROUGH THE UPPER MS AND MID MO
RIVER VALLEYS. MEANWHILE...A WARM FRONT LOCATED FROM LOW PRESSURE
OVER CNTRL KS NEWD THROUGH CNTRL IA INTO CNTRL PARTS OF IL/IND/OH AS
OF 15Z WILL CONTINUE NWD INTO THE GREAT LAKES WITHIN A PERSISTENT
LOW-LEVEL WAA REGIME.

...GREAT LAKES INTO OH VALLEY...

THE RESPONSE TO A LEAD SHORTWAVE TROUGH TRACKING FROM THE NRN/CNTRL
PLAINS THROUGH THE GREAT LAKES AND MID MS VALLEY WILL RESULT IN THE
BROADENING AND STRENGTHENING OF A SWLY LLJ FROM THE OZARK PLATEAU
INTO THE GREAT LAKES. THIS FEATURE WILL HASTEN THE NWD FLUX OF
LOW-LEVEL HEAT AND MOISTURE BENEATH GRADUALLY STEEPENING MIDLEVEL
LAPSE RATES...YIELDING A WEAKLY UNSTABLE ENVIRONMENT FOR PARCELS
ROOTED IN THE 900-850-MB LAYER. THE COUPLING OF DCVA ATTENDANT TO
THE SHORTWAVE TROUGH AND LOW-LEVEL WAA/ISENTROPIC ASCENT ALONG THE
LLJ WILL FOSTER ISOLATED TO WIDELY SCATTERED ELEVATED TSTMS THIS
EVENING INTO TONIGHT FROM SERN WI AND LOWER MI INTO PARTS OF THE OH
VALLEY. NO SEVERE WEATHER IS EXPECTED.

...WA/NRN ORE COASTS...

MOIST...ONSHORE FLOW IN THE LOW LEVELS WILL ALIGN WITH STEADILY
COOLING MIDLEVEL TEMPERATURES ASSOCIATED WITH THE APPROACH OF THE
UPPER-LEVEL SYSTEM MENTIONED IN THE SYNOPSIS TO YIELD A WEAKLY
UNSTABLE ENVIRONMENT. WHILE SPORADIC BURSTS OF LIGHTNING AND GUSTY
WINDS WILL BE POSSIBLE WITH CONVECTIVE RAINBANDS MOVING ONSHORE...NO
SEVERE WEATHER IS ANTICIPATED.

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