Brisk Wind Advisory 63, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
350 AM AKDT MON APR 27 2009

.MODEL DISCUSSION...

THE GFS IS THE ONCE AGAIN THE PREFERRED MODEL IN THE SHORT
TERM...WITH THE NAM USED OVER LAND AREAS IN THE IMMEDIATE SHORT TERM
WHERE ITS ENHANCED SPATIAL RESOLUTION WAS BENEFICIAL IN GENERATING
GRIDS.

.ANALYSIS AND UPPER LEVELS...

SURFACE HIGH PRESSURE RIDGING FROM THE GULF OF ALASKA NORTHWARD ALONG
THE ALCAN BORDER AREA CONTINUES.  MEANWHILE...WEAKENING LOW PRESSURE
IN THE NORTHERN BERING SEA ASSOCIATED WITH A MID-LEVEL TROUGH IS
BRINGING MOSTLY CLOUDS TO THE EASTERN ALEUTIANS.  IN BETWEEN THE LOW
PRESSURE SYSTEM AND THE HIGH PRESSURE RIDGE OVER THE GULF OF
ALASKA...STRONG SOUTHERLY FLOW IS PUMPING LOTS OF MOISTURE OVER THE
ALASKA PENINSULA...BRISTOL BAY...AND INTO THE KUSKOKWIM VALLEY.  THIS
REGION IS ALSO IN THE FAVORABLE RIGHT ENTRANCE REGION OF A 300-MB
LEVEL JET STREAK...AND A STATIONARY FRONT CONTINUES TO RESIDE
UNDERNEATH THIS FEATURE AT THIS SURFACE...PROVIDING A FOCUS FOR
WIDESPREAD PRECIPITATION.  ELSEWHERE...WEAK RIDGING IS LOCATED OVER
THE WESTERN ALEUTIANS AND SOUTHWESTERN BERING SEA.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...

HIGH PRESSURE BUILDS FROM THE SOUTH AND EAST OVER SOUTHCENTRAL TODAY.
THIS WILL RESULT IN DIMINISHING THE PRESSURE GRADIENT THROUGH
TURNAGAIN ARM...AND THUS EXPECT TO SEE CONTINUED SLACKENING OF THE
WINDS.  SOUTHERLY FLOW TODAY WILL RESULT IN PRECIPITATION CONTINUING
MOSTLY OVER THE HIGHER ELEVATIONS...WITH JUST ISOLATED SHOWERS IN THE
LOWER ELEVATIONS.  OTHERWISE...AS A STRONG LOW PRESSURE SYSTEM
APPROACHES THE WESTERN ALEUTIANS TONIGHT AND HIGH PRESSURE BUILDS
OVER THE REGION...EXPECT MOSTLY TRANQUIL WEATHER ACROSS THE
REGION...THOUGH THE POSSIBILITY OF FOG AND/OR LOW STRATUS WILL BE
MENTIONED OVER THE COPPER RIVER BASIN...PRINCE WILLIAM SOUND...AND
PARTS OF COOK INLET REGION UNDERNEATH A NOCTURNAL SUBSIDENCE
INVERSION NEAR THE SURFACE AND WITH MOISTURE ADVECTION FROM THE GULF
WATERS.  WITH TEMPERATURES WARMING UP APPRECIABLY UNDER SUNNY SKIES
DURING THE AFTERNOON HOURS FOR THE NEXT FEW DAYS...WILL NEED TO
MONITOR WINDS ALONG COASTAL LOCATIONS FOR SEA BREEZES.
OTHERWISE...EXPECT MOSTLY DRY AND CLEAR WEATHER CONDITIONS THROUGH
WEDNESDAY NIGHT.

WEST OF THE ALASKA/ALEUTIAN RANGES...

THE BIG ISSUE THROUGH WEDNESDAY NIGHT IS FIGURING OUT WHERE EXACTLY
THE MOISTURE PLUME SETS UP.  FOR TODAY...EXPECT TO SEE RAINFALL
CONTINUING WITH HEAVIEST PRECIPITATION FALLING FROM THE CENTRAL
ALASKA PENINSULA NORTHWARD THROUGH THE KUSKOKWIM VALLEY UP TOWARDS
MCGRATH.  AS THE RIDGE BUILDS TOWARDS THE WEST AND STRENGTHENS
TOWARDS WEDNESDAY NIGHT...AN UPPER TROUGH APPROACHING THE WESTERN
ALEUTIANS TODAY BEGINS DIGGING TO THE SOUTH OF THE ALEUTIAN CHAIN
THIS EVENING. THUS...THE STRONG SOUTHERLY FLOW WILL BACK TO
SOUTHEASTERLY AND DIRECT THE HEAVIEST PRECIPITATION FROM OVER THE
ALASKA PENINSULA NORTHWARD ACROSS BRISTOL BAY AND OVER THE KUSKOKWIM
DELTA REGION BEGINNING TODAY.  THIS REGION OF HEAVIEST PRECIPITATION
WILL THEN GRADUALLY SHIFT WESTWARD TO MOSTLY OVER THE BERING SEA AND
EASTERN ALEUTIANS AS WE HEAD TOWARDS WEDNESDAY NIGHT.

BERING SEA AND THE ALEUTIAN CHAIN...THE AFOREMENTIONED NEXT SYSTEM TO
AFFECT THE REGION WILL ENTER THE WESTERN ALEUTIANS THIS AFTERNOON AND
THEN OVERTAKE THE CENTRAL ALEUTIANS TUESDAY AFTERNOON WITH UNSETTLED
WEATHER.  THE GFS AND ECMWF MODELS FORECAST A POTENTIALLY POTENT
SHORTWAVE WITH ASSOCIATED SURFACE LOW MOVING ALONG IN THE
SOUTHEASTERLY FLOW ACROSS THE EASTERN ALEUTIANS OR SOUTHERN AKPEN
INTO THE BERING SEA LATE TUESDAY NIGHT OR EARLY WEDNESDAY...BUT THIS
STILL BEARS WATCHING TO FIGURE OUT HOW EXACTLY THE FLOW ORIENTS
ITSELF GIVEN RELATIVELY POOR CONSISTENCY OF THE STRENGTH AND
ORIENTATION OF THE TROUGH OVER THE WESTER BERING/ALEUTIANS.  IF IT
VERIFIES...HOWEVER...THERE COULD BE HEAVIER PRECIPITATION WITH GALE
FORCE WINDS ACROSS THE ALASKA PENINSULA AND BRISTOL BAY LATE TUESDAY
NIGHT INTO WEDNESDAY.

.LONG TERM FORECAST...

HIGH PRESSURE WILL LIKELY STILL BE IN CONTROL OF THE NORTHERN AND
EASTERN PART OF THE REGION FROM THURSDAY THROUGH THE WEEKEND.  A
LARGE LOW PRESSURE SYSTEM WILL TAKE CONTROL OF THE SOUTHWESTERN GULF
OF ALASKA...THE NORTH PACIFIC OCEAN...AND THE ALEUTIAN CHAIN
BEGINNING FRIDAY.  THIS WILL LIKELY MEAN SOUTHEASTERLY FLOW IS LIKELY
ACROSS MOST OF THE SOUTHWEST ALASKA MAINLAND...WITH THE BEST CHANCES
OF UNSETTLED WEATHER FROM THERE DOWN THROUGH THE ALEUTIANS.  MOSTLY
FAIR WEATHER WITH SURFACE HIGH PRESSURE IN THE VICINITY LOOKS
POSSIBLE FROM THURSDAY THROUGH MONDAY FOR MOST OF THE EASTERN DOMAIN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE...172 175 176
FIRE WEATHER...NONE.

CC APR 09