Brisk Wind Advisory 67, NWS Anchorage, AK

AREA FORECAST DISCUSSION...CORRECTED
SOUTHCENTRAL AND SOUTHWEST ALASKA
215 PM AKDT THU MAY 13 2010

.ANALYSIS AND UPPER LEVELS...
LONG WAVE TROUGH ANCHORED OVER THE EASTERN BERING SEA WITH THREE
DISTINCT SHORTWAVES ROTATING AROUND ITS PERIPHERY. THE FIRST IS
LOCATED OVER SOUTHCENTRAL AND IS CURRENTLY ENHANCING THE CLOUD
COVERAGE AND SHOWER ACTIVITY OVER THE REGION. A SECOND IS LOCATED
SOUTH OF THE ALASKA PENINSULA...WHICH IS HELPING TO INITIATE A
SURFACE LOW THAT WILL DEVELOP AND MOVE INTO THE WESTERN GULF TONIGHT.
THE THIRD IS DROPPING SOUTH ACROSS THE WESTERN ALEUTIANS.

THE SURFACE FEATURES MIRROR THE UPPER LEVELS...WITH ONLY WEAK SURFACE
LOWS VERTICALLY STACKED UNDERNEATH THEIR COUNTERPARTS ALOFT. A RIDGE
HAS BUILT ALONG THE NORTH GULF COAST BETWEEN THE TWO WEAK SURFACE
LOWS. THIS COMMON SUMMER FEATURE IS BRINGING GUSTY WINDS TO THE
TYPICAL AREAS INCLUDING TURNAGAIN ARM...SOUTH AND WEST
ANCHORAGE...KNIK VALLEY...AND THE COPPER RIVER VALLEY. SHOWER
ACTIVITY IS MOST PRONOUNCED ALONG THE COAST WITH MOSTLY VIRGA
PREVAILING INLAND.

.MODEL DISCUSSION...MODELS QUICKLY DIVERGE IN THE FIRST 36 HOURS...IN
PARTICULAR THE LOW THAT DEVELOPS TONIGHT SOUTH OF KODIAK ISLAND. THE
LOW WILL BE ESSENTIALLY STACKED UNDER THE UPPER LOW AND THEREFOR
WOBBLING A BIT AS IT DEEPENS AND ROTATES NORTH INTO THE GULF. THE
DIFFERENT LOCATIONS OF THE LOW CAN BE TRACED TO THE DISPARITIES IN
THE STRENGTH AND RATE AT WHICH THE MODELS DEVELOP THE LOW OVERNIGHT.
THE STRONGEST SOLUTION IS THE NAM...WHICH TAKES THE LOW FURTHEST
NORTHWEST NEAR KODIAK CITY WHEREAS THE ECMWF IS THE WEAKEST AND KEEPS
THE LOW MORE VERTICALLY STACKED AND THEREFOR FARTHER TO THE SOUTH AND
EAST. BASED ON SATELLITE AND A FEW OBS OVER THE NORTHERN PACIFIC...WE
ARE LEANING AWAY FROM THE ECMWF WEAK SOLUTION AND MORE TOWARD A
COMPROMISE WHICH IN THE FIRST 48 HOURS IS THE GFS. THE LOCAL WRF
MODEL DEPICTS THE LOW SIMILARLY TO THE GFS AS WELL AS PICKING UP ON
MANY OF THE LOCAL WIND EFFECTS...SO UTILIZED THE LOCAL WRF IN THE
FIRST 24 HOURS BEFORE TRENDING TOWARD THE GFS THROUGH 60 HOURS. NO
CHANGES WERE MADE PAST 60 HOURS.

.SHORT TERM FORECAST...
SOUTHCENTRAL...THE CHALLENGE IN THE SHORT TERM WILL BE DETERMINING
THE COVERAGE OF THE ONGOING SHOWER ACTIVITY AND WHETHER THE VIRGA
WILL TURN INTO SHOWERS THAT REACH THE GROUND. THE 12Z SOUNDING
PROBABLY IS NOT A GOOD INDICATION OF THE CURRENT MOISTURE PROFILE
SINCE A MUCH DRIER AIRMASS MOVED ACROSS THE AREA OVERNIGHT. THE BEST
BET IS LIKELY PERSISTENCE...WHICH MEANS SOME SHOWERS WILL REACH THE
GROUND BUT MOST WILL NOT...AND THE ONES THAT DO WILL BE LIGHT AND NOT
LAST VERY LONG.

GAP WINDS WILL DIMINISH OVERNIGHT AS THE RIDGE ALONG THE COAST BREAKS
DOWN AND THE LOW MOVES NEAR KODIAK ISLAND. THE GRADIENT BECOMES
ORIENTED MORE NORTH SOUTH WHICH WILL FAVOR DRIER AIR AT THE SURFACE
AND WEAKER WINDS. MOISTURE WILL BE CONCENTRATED ALONG THE COAST AS
THE LOW MOVES TOWARD THE SOUTHERN KENAI PENINSULA SATURDAY.
STILL...ONLY EXPECTING SCATTERED SHOWER ACTIVITY THROUGH THE WEEKEND
WITH NO REAL PROLONGED PERIOD OF STRATIFORM RAIN.

HIGH PRESSURE BUILDS FROM THE YUKON TERRITORY SUNDAY. COUPLED WITH A
DRYING TREND...THE RETURN OF SOME WARMER THAN AVERAGE TEMPERATURES
AND OVERALL PLEASANT CONDITIONS ARE ON THE HORIZON FOR EARLY NEXT
WEEK.

SOUTHWEST INTERIOR...
SIMILAR FORECAST THROUGH FRIDAY AS SOUTHCENTRAL WITH MOSTLY CLOUDY
CONDITIONS WITH SCATTERED SHOWERS. THE DIFFERENCE WILL BE FRIDAY
EVENING WHEN THE UPPER LEVEL SUPPORT MOVES INLAND...SPREADING AN AREA
OF STRATIFORM RAIN FROM BRISTOL BAY UP TO THE KUSKOKWIM VALLEY.
CONVECTIVE INDEXES LOOK UNIMPRESSIVE AT THIS TIME AS THE ENERGY MOVES
ACROSS THE REGION. IT IS NOT UNTIL THE SHORTWAVE REACHES A MORE
UNSTABLE AIRMASS OVER THE LOWER YUKON WHEN THUNDERSTORM ACTIVITY
BECOMES A POSSIBILITY SATURDAY AFTERNOON.

ONLY A BRIEF BREAK IN THE ACTION BEFORE ANOTHER LOW MOVES TOWARD THE
ALASKA PENINSULA SUNDAY...BRINGING MORE RAIN TO THE COAST AND SHOWER
ACTIVITY INLAND THROUGH EARLY NEXT WEEK.

BERING SEA/ALEUTIANS...SEVERAL WEAK LOWS WILL CONTINUE TO DEVELOP AND
THEN WEAKEN THROUGH EARLY NEXT WEEK. MOST OF THESE CIRCULATIONS WILL
ONLY BRING MINIMUM SMALL CRAFT WINDS TO THE REGION. THE EXCEPTION
WILL BE THE LOW THAT DEVELOPS SOUTH OF THE CHAIN AND THEN EVENTUALLY
MOVES TO SOUTH OF THE ALASKA PENINSULA SATURDAY EVENING. SOME GALE
FORCE WINDS ARE EXPECTED WITH THIS SYSTEM AS IT DISPLAYS MUCH MORE
BAROCLINICITY THAN ITS PREDECESSORS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 120 130 138 150.
FIRE WEATHER...NONE.

AB MAY 10