Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 241328
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
528 AM AKDT TUE MAR 24 2015

.ANALYSIS AND UPPER LEVELS...
RIDGING OVER THE SOUTHCENTRAL IS SLOWLY MOVING EAST. THE RIDGING
HAS KEPT THE MAJORITY OF THE ACTIVITY OUT WEST WHICH HAS RESULTED
IN CLEAR SKIES AROUND THE SOUTHCENTRAL AND SOUTHWEST. THE MAIN
UPPER LOW SITS OVER THE EASTERN ALEUTIANS AND IS RELATIVELY
STATIONARY KEEPING SOUTHEASTERLY FLOW OVER MUCH OF THE SOUTHERN
MAINLAND. ANOTHER LOW IS MOVING TOWARDS THE AREA FROM THE NORTH
PACIFIC AND IS HEADING TOWARDS KODIAK ISLAND.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT THROUGH THE SHORT
TERM ONCE AGAIN. FORECAST CONFIDENCE IS THUS ABOVE NORMAL TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (TODAY THROUGH WEDNESDAY
NIGHT)...
A TRANSITION IN THE PATTERN WILL BEGIN TODAY AS A
DEEPENING STORM SYSTEM OVER THE NORTHEAST PACIFIC TRACKS NORTHWARD
TOWARD KODIAK ISLAND HELPING TO PUSH THE UPPER RIDGE SITTING OVER
SOUTHCENTRAL OFF TO THE NORTH AND EAST. THERE WILL BE ONE MORE DAY
OF WARM AND SUNNY CONDITIONS BEFORE CLOUDS BEGIN TO MOVE INTO THE
REGION TONIGHT INTO WEDNESDAY.

FORECAST CONFIDENCE HAS INCREASED WITH THE TRACK AND STRENGTH OF
THIS STORM SYSTEM. THE SYSTEM WILL NOT DEEPEN ALL THAT MUCH FROM
ITS CURRENT PRESSURE BUT IT WILL BE MOVING INTO AN AREA OF
RELATIVELY HIGH PRESSURE. IN ADDITION...UPPER LEVEL DYNAMICS ARE
IMPRESSIVE WITH A STRONG JET STREAK AND POTENT UPPER LEVEL WAVE
EJECTING OUT OF THE TROUGH AND ACROSS THE GULF. THUS...HAVE
TRENDED STRONGER WITH THE WINDS AND HIGHER WITH THE QPF ACROSS
THE GULF WATERS TONIGHT THROUGH WEDNESDAY NIGHT.

AS IS TYPICAL WITH A SYSTEM LIKE THIS...THE BRUNT OF THE STORM
WILL AFFECT THE COASTAL REGION AND KODIAK ISLAND. THE MOST
SIGNIFICANT THREAT INLAND IS FOR RED FLAG CONDITIONS IN THE
MATANUSKA VALLEY OUT AHEAD OF THE STORM WEDNESDAY AFTERNOON AND
EVENING. A FIRE WEATHER WATCH HAS BEEN ISSUED TO HIGHLIGHT THIS
THREAT. THERE IS HIGH CONFIDENCE THAT STRONG GUSTY WINDS WILL
DEVELOP. THE BIG QUESTION IS HOW LOW RELATIVE HUMIDITIES WILL
DROP PRIOR TO THE ARRIVAL OF CLOUDS. IN ANY CASE...WITH NO SNOW
ON THE GROUND RELATIVELY WINDY AND DRY CONDITIONS WILL INCREASE
THE FIRE DANGER.

STRONG CROSS BARRIER FLOW WILL DEVELOP ACROSS THE KENAI AND
CHUGACH MOUNTAINS WHICH WILL PRODUCE SOME DOWNSLOPING DRYING.
HOWEVER...THIS LOOKS LIKE A GOOD CASE FOR A LITTLE BIT OF
SLOP-OVER PRECIP WITH THE CORE OF WINDS WELL ABOVE MOUNTAIN
TOP...A STRONG UPPER LEVEL SHORT-WAVE MOVING THROUGH...AND
DESTABILIZATION OF THE ABOVE MOUNTAIN LAYER AS THE WAVE MOVES
THROUGH. THE BEST CHANCE FOR PRECIP INLAND AND IN THE LEE OF THE
MOUNTAINS IS WEDNESDAY NIGHT. THE COMBINATION OF THE LOW LEVEL
WINDS AND WARM ADVECTION AS THE SURFACE FRONT MOVES ONSHORE
MEANS THE PREDOMINANT PRECIP-TYPE WILL BE RAIN.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TODAY AND WEDNESDAY)...
HIGH PRESSURE ALOFT OVER THE MAINLAND WILL SLOWLY GIVE WAY TO
CLOUD COVER AHEAD OF AN APPROACHING FRONT FROM THE PACIFIC.
PRECIPITATION WILL REMAIN SCANT AND MAINLY BE CONFINED TO THE
KUSKOKWIM DELTA COAST AND BRISTOL BAY COAST. EAST WINDS WILL
CONTINUE TO SLOWLY INCREASE THROUGH THE DAY AND GET GUSTY IN THE
AFTERNOON. OVERNIGHT INTO WEDNESDAY A FRONTAL BOUNDARY WILL SPREAD
INTO BRISTOL BAY BRINGING RAIN FROM THE ALASKA PENINSULA NORTHWARD
INTO INTERIOR BRISTOL BAY WHILE AREAS IN THE LEE OF THE ALEUTIAN
RANGE SHOULD REMAINED DRIER IN DOWNSLOPE CONDITIONS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TODAY AND WEDNESDAY)...
MOST OF THE BERING WILL REMAIN UNDER CYCLONIC FLOW OF THE
PERSISTENT UPPER LOW FOR THE PAST WEEK. THIS WILL BRING SNOW
SHOWERS FROM THE PRIBILOF ISLANDS AND WESTWARD WHILE THE EASTERN
ALEUTAINS AND ALASKA PENINSULA WILL SEE RAIN SHOWERS AND WARMER
TEMPERATURES. A FRONTAL BOUNDARY ASSOCIATED WITH A NORTH PACIFIC
LOW PRESSURE SYSTEM WILL MOVE INTO THE EASTERN BERING SEA ON
WEDNESDAY BRINGING SNOW...RAIN...AND THE POSSIBILITY FOR BLIZZARD
CONDITIONS FOR THE PRIBILOF ISLANDS.

&&

.LONG TERM FORECAST (THURSDAY THROUGH MONDAY)...
AS THE FRONT DISSIPATES OVER THE NORTH GULF COAST AND ITS
ASSOCIATED LOW APPROACHES KODIAK ISLAND ON THURSDAY...GUSTY WINDS
ARE EXPECTED TO DEVELOP FROM WESTERN PRINCE WILLIAM SOUND...THROUGH
TURNAGAIN ARM AND INTO THE ANCHORAGE AREA. THESE WINDS WILL THEN
BEGIN TO DIMINISH LATE THURSDAY NIGHT AS THE LOW CENTER MOVES
INLAND AND THE PRESSURE GRADIENT BEGINS TO DROP. DEEP SOUTHERLY
FLOW OVER THE GULF WILL ALSO BRING CONTINUED RAIN THROUGHOUT THE
GULF COAST FOR THURSDAY AND FRIDAY...WITH CHANCES OF RAIN
INCREASING FOR INTERIOR SOUTHCENTRAL STARING THURSDAY EVENING AS
DOWNSLOPING CONDITIONS DETERIORATE.

AN ACTIVE WEATHER PATTERN REMAINS ON TAP FROM THIS WEEKEND THROUGH
EARLY NEXT WEEK AS LOW PRESSURE REMAINS DOMINANT THROUGH THE
EXTENDED FORECAST. ANOTHER GULF LOW IS EXPECTED TO MOVE INTO THE
GULF LATE FRIDAY INTO SATURDAY...AND THEN STALL OUT AS IT WEAKENS
OVER THE GULF ON SUNDAY. THIS WILL BRING CONTINUED STORMY WEATHER
TO THE GULF COAST...WITH PERSISTENT NORTHERLY FLOW OVER THE
EASTERN BERING REGION.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...BLIZZARD WATCH 195.
MARINE...STORM 130 131 138
         GALE 119 132 136 137 139 150 160.
         HEAVY FREEZING SPRAY 179
FIRE WEATHER...FIRE WEATHER WATCH 111.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...DK
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...DEK/KH



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