Small Craft Advisory 432, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT WED JUN 13 2012

.ANALYSIS AND UPPER LEVELS...
A POWERFUL UPPER LEVEL LOW THAT IS CENTERED OVER FAIRBANKS WILL DRIFT
SOUTHWARD TOWARDS THE GULF OVER THE NEXT 48 HOURS. THIS SYSTEM IS
PARTICULARLY STRONG AND COLD FOR THIS TIME OF YEAR...AND WILL
CONTINUE TO STEEPEN LAPSE RATES AND SUPPORT CONVECTION AS IT MOVES
SOUTHWARD. OVER THE BERING...AN UPPER LEVEL OMEGA BLOCK IS SETTLING
INTO PLACE AND IS BEING PINCHED OFF FROM ANY DRIVING UPPER LEVEL
FLOW.

.AT THE SURFACE...WIDESPREAD SHOWERS AND CLOUD COVER WILL KEEP A WELL
DEVELOPED THERMAL TROUGH FROM FORMING ACROSS THE INTERIOR TODAY. A
WEAK LOW IN THE GULF WILL SLOWLY STRENGTHEN AS THE UPPER LEVEL LOW
MOVES SOUTHWARD. A RELATIVELY WEAK RIDGE WILL BUILD ALONG THE GULF
COAST AND WILL SUPPORT LIGHT WINDS THROUGH LOCAL GAPS. A MUCH MORE
POTENT LOW IS LOCATED SEVERAL HUNDRED MILES SOUTH OF THE CENTRAL
ALEUTIANS. HOWEVER...ITS ASSOCIATED FRONT WILL APPROACH THE CENTRAL
AND WESTERN ALEUTIANS AS EARLY AS TONIGHT.

.MODEL DISCUSSION...MODELS ARE IN RELATIVELY GOOD AGREEMENT
SYNOPTICALLY IN THE SHORT TERM...WITH THE GFS THE SLIGHT OUTLIER. IN
THE LONG TERM MODELS DIVERGE MORE SIGNIFICANTLY AND HPC GUIDANCE WAS
FAVORED.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

AFTERNOON CONVECTION CONTINUES TO BE A CHALLENGE TO PREDICT ACROSS
THE SOUTHCENTRAL REGION FOR THIS AFTERNOON. THE COLD UPPER LEVEL LOW
WILL STEEPEN LAPSE RATES ACROSS THE ENTIRE REGION AS IT MOVES
SOUTHWARD. HOWEVER...THE SURFACE THERMAL TROUGH WILL BE WEAK
TODAY...AND DIURNAL HEATING WILL BE LIMITED DUE TO WIDESPREAD CLOUD
COVER. THE BEST CHANCE FOR A LIGHTNING STRIKE WILL BE ALONG THE
WESTERN FRINGE OF THE MATANUSKA VALLEY WHERE UPPER LEVEL FORCING IS
MORE FAVORABLE.  HOWEVER...THUNDERSTORMS COULD FORM FARTHER EAST IF
MORE DIURNAL HEATING OCCURS THAN MODELS ARE CURRENTLY PREDICTING.

SHOWERS WILL CONTINUE TO DOMINATE THE WEATHER INTO THURSDAY AS THE
UPPER LEVEL LOW DRIFTS INTO THE GULF AND WEAKENS. AFTERNOON BREAKS IN
THE CLOUDS ALONG THE BACK OF THIS LOW SHOULD ALLOW FOR ENOUGH
AFTERNOON HEATING FOR MORE WIDESPREAD CONVECTION ACROSS SOUTHCENTRAL
BY THURSDAY.

SOUTHWEST...

A STRATUS DECK CONTINUES TO LINGER ALONG THE BRISTOL BAY COAST AND
HAS SURGED INLAND ACROSS THE KUSKOKWIM DELTA OVERNIGHT. DIURNAL
HEATING SHOULD HELP TO BRING SOME BREAKS IN THE STRATUS BY THIS
AFTERNOON ACROSS THE DELTA. THE WEATHER WILL BE MUCH MORE ACTIVE
ACROSS THE KUSKOKWIM VALLEY AND INLAND AREAS OF THE BRISTOL BAY ZONE
THIS AFTERNOON. AS THE UPPER LEVEL LOW AND ITS ASSOCIATED JET MOVE
SOUTHWARD...BOTH OF THESE REGIONS WILL BE IN THE IDEAL LOCATION OF
UPWARD VERTICAL MOTION. AS A RESULT...A FEW THUNDERSTORMS WILL BE
POSSIBLE THIS AFTERNOON AND THURSDAY AFTERNOON.

BERING SEA/ALEUTIANS...

A STUBBORN OMEGA BLOCK CONTINUES TO SUPPORT A STRATUS DECK AND QUIET
CONDITIONS ACROSS THE BERING. A FRONT ASSOCIATED WITH A LOW IN THE
NORTH PACIFIC WILL BRING GUSTY WINDS AND RAIN TO THE CENTRAL AND
WESTERN ALEUTIANS BEGINNING THIS EVENING. THIS FRONT WILL LINGER INTO
THURSDAY...AND CONTINUE TO SUPPORT GUSTY WINDS AS IT SLOWLY
DISSIPATES.

.LONG TERM FORECAST...MODELS INDICATE A GRADUAL RETURN TO A MORE
SUMMER LIKE PATTERN WITH A RIDGE BUILDING ACROSS THE MAINLAND BY THE
BEGINNING OF NEXT WEEK. HOWEVER...THERE IS STILL A LOT OF UNCERTAINTY
IN THE LONG TERM FORECAST...AND MODELS ALSO INDICATE ANOTHER STRONG
COLD UPPER LOW LURKING IN THE ARCTIC.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES..172 175.
FIRE WEATHER...NONE.

ELN JUN 12