Gale Warning 687, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
950 PM AKST SAT NOV 22 2014

UPDATE (945 PM)...

SATELLITE TRENDS SEEM TO BE CORROBORATING 00Z NAM AND GFS MODEL
TRENDS IN DEPICTING INCREASED POTENTIAL FOR A BRIEF BURST OF SNOW
TO IMPACT THE ANCHORAGE AND NEIGHBORING COMMUNITIES LATER
TONIGHT...MAINLY BETWEEN MIDNIGHT AND 4 AM. DUE TO THE QUICK
MOVEMENT OF THE SYSTEM...SNOW ACCUMULATIONS SHOULD BE NO MORE THAN
AN INCH OR SO AT MOST BUT COULD BE IMPACTFUL FOR THE EARLY SUNDAY
MORNING TRAVEL INTERESTS GIVEN THE SNOW-FREE CONDITIONS CURRENTLY.

&&

.PREV DISCUSSION... /ISSUED 435 PM AKST SAT NOV 22 2014/

ANALYSIS AND UPPER LEVELS...

A STACKED AND WEAKENING 970S LOW CENTER JUST WEST OF SAND POINT
IS SLOWLY DRIFTING ESE AND WEAKENING. RAIN AND SHOWERS ASSOCIATED
WITH THIS FEATURE WERE OBSERVED OVER THE AK PENINSULA. BRISK
NORTHERLY WINDS AND SHOWERS WERE EVIDENT ON THE BACKSIDE OF THE
CENTER OVER THE CENTRAL AND EASTERN ALEUTIANS. AN UPPER LEVEL WAVE
AND WEAK SURFACE REFLECTION JUST SOUTH OF WESTERN PRINCE WILLIAM
SOUND WAS MOVING NORTH AND WEST. RADAR IMAGERY SHOWERS ENHANCED
RETURNS HEADING TOWARD THE EASTERN KENAI PENINSULA WITH RAIN AND
SHOWERS REPORTED AT STATIONS THIS AFTERNOON. TEMPS ALONG THE GULF
COAST...BRISTOL BAY...AND AK PEN/ALEUTIANS CONTINUED FAIRLY MILD.
WEAK COLD ADVECTION WITH OFFSHORE FLOW DROPPED TEMPS OVER THE
DELTA INTO THE TEENS. COLDEST TEMPS ACROSS THE FORECAST AREA WERE
STILL IN THE COPPER RIVER BASIN WITH VALUES FROM -2 TO SINGLE
DIGITS ABOVE IN LOW LYING AREAS.

MODEL DISCUSSION(SHORT TERM)...
MODELS INITIALIZED FAIRLY WELL THIS MORNING. FORECAST TRENDS ARE
IN GOOD AGREEMENT THROUGH THE SHORT TERM. THE GEM REGIONAL WAS
USED IN THE WEST DURING THE EARLY PART OF THE SHORT TERM WITH A
TRANSITION INTO A NAM/EC BLEND FOR THE REMAINDER. IN THE
EAST...THE NAM WILL BE USED EARLY ON FOLLOWED BY A TRANSITION TO A
NAM/EC BLEND.

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A DISSIPATING FRONT ALONG THE NORTH GULF COAST AND A SERIES OF
WEAK DISTURBANCES ROTATING THROUGH THE GULF WILL KEEP SHOWER
ACTIVITY FOCUSED MAINLY ALONG THE COAST THROUGH MONDAY. THE FIRST
OF THESE UPPER WAVES WILL HELP TO SPREAD SNOW SHOWERS OVER INLAND
PORTIONS OF THE AREA TONIGHT AS DOWNSLOPE FLOW WEAKENS...ALTHOUGH
DRY AIR AT THE SURFACE WILL KEEP THESE SHOWERS FAIRLY LIMITED IN
COVERAGE. ANOTHER WAVE WILL THEN MOVE THROUGH LATER SUNDAY AND
PROVIDE ANOTHER SHOT OF ENHANCED SHOWER ACTIVITY. SHOWERS WILL
BEGIN TO DIMINISH ACROSS THE AREA MONDAY NIGHT INTO TUESDAY AS THE
LOW CURRENTLY OVER THE ALASKA PENINSULA WEAKENS INTO AN OPEN
TROUGH AND MOVES EAST OF THE AREA.

SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)...
WITH THE EXCEPTION OF SOUTHERN BRISTOL BAY...MOST OF THE SOUTHWEST
MAINLAND WILL REMAIN UNDER PARTLY TO MOSTLY CLOUDY SKIES THROUGH
THE END OF THE WEEKEND. ISOLATED TO SCATTERED RAIN/SNOW SHOWERS
MAY FORM IN THE AREA ON SUNDAY AS A WEAK ELONGATED UPPER LEVEL
TROUGH DEVELOPS...HOWEVER THESE SHOULD LARGELY BE LIMITED TO
SOUTHERN BRISTOL BAY. TEMPERATURES ARE EXPECTED TO FALL INTO THE
SINGLE DIGITS OVER IN NEXT FEW NIGHTS IN THE KUSKOKWIM VALLEY AND
INLAND BRISTOL BAY AS THE LOW NEAR THE AKPENN CONTINUES TO SLOWLY
WEAKEN...AND WEAK RIDGING BEINGS TO DEVELOP. THESE TEMPERATURES
WILL THEN CONTINUE UNDER MOSTLY CLEAR SKIES UNTIL TUESDAY WHEN A
WEAK FRONT SLIDES ONSHORE FROM THE BERING.

SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3)...

THE LOW CENTERED JUST SOUTH OF THE AKPENN WILL CONTINUE TO BRING
SNOW SHOWERS TO THE BERING...BECOMING RAIN SHOWERS TOWARDS THE
ALEUTIAN ISLANDS THROUGH THIS WEEKEND. THE GUSTY NORTHWESTERLY
WINDS ACCOMPANYING THESE SHOWERS WILL SLOWLY DIMINISH THIS
WEEKEND...THEN DISSIPATE ON MONDAY AS RIDING BEGINS TO TAKE OVER.
A FRONTAL SYSTEM ASSOCIATED WITH AN LOW LOCATED OFF THE KAMCHATKA
PENINSULA COAST WILL BEGIN TO IMPACT THE WESTERN ALEUTIANS WITH
RAIN AND GALE FORCE WINDS ON SUNDAY EVENING. THIS SYSTEM WILL THEN
MOVE THROUGH THE BERING AS IT SLOWLY DISSIPATES THROUGH MONDAY.

LONG TERM FORECAST (DAYS 3 THROUGH 7)...
A WEAK LOW OVER THE WESTERN GULF WILL CONTINUE TO WEAKEN AS IT
DRIFTS EASTWARD...KEEPING MOST OF THE SHOWER ACTIVITY CONFINED TO
THE NORTH GULF COAST AND KODIAK ISLAND BEFORE DISSIPATING ON
TUESDAY. UPPER LEVEL RIDGING OVER THE EASTERN ALEUTIANS WILL BEGIN
TO AMPLIFY AND SLIDE EASTWARD OVER THE SOUTHWEST MAINLAND AND
SOUTHCENTRAL ALASKA BY TUESDAY AFTERNOON. THIS WILL BRING IN SOME
DRIER CONDITIONS TO THE INTERIOR SOUTHWEST MAINLAND THROUGH
WEDNESDAY MORNING...AND TO SOUTHCENTRAL ALASKA THROUGH WEDNESDAY
EVENING. EVEN THOUGH CURRENT GUIDANCE IS IN GOOD AGREEMENT WITH
A BLOCKING RIDGE SETTING UP OVER THE EASTERN DOMAIN BY MID
WEEK...THE MODELS CONTINUE TO STRUGGLE WITH THE TIMING AND
STRENGTH OF SMALLER SCALE DISTURBANCES AND LOW POSITIONING OVER
THE WESTERN DOMAIN THROUGH MUCH OF THE LONG TERM. GLOBAL MODELS
AND WPC GUIDANCE ARE GETTING CLOSER TO A COMMON SOLUTION REGARDING
THE TRIPLE POINT LOW DEVELOPING OVER THE NORTH PACIFIC TUESDAY
AFTERNOON...BUT CONTINUE TO QUICKLY DIVERGE FROM THAT SOLUTION BY
TUESDAY NIGHT. MODELS TYPICALLY STRUGGLE WITH THIS TYPE OF
DEVELOPMENT...WHICH HAS CREATED HIGHER UNCERTAINTY WITH REGARDS TO
THE TIMING/STRENGTH OF WINDS AND PRECIPITATION THAT CAN IMPACT THE
ALASKA PENINSULA AND SOUTHWEST MAINLAND STARTING TUESDAY NIGHT.
FURTHER WEST...A DEVELOPING LOW EAST OF THE KAMCHATKA PENINSULA
WILL BEGIN TO PHASE WITH ANOTHER LOW PRESSURE SYSTEM TO THE SOUTH
ON TUESDAY...AND TRACK OVER THE WESTERN ALEUTIANS ON WEDNESDAY.
THE FRONT ASSOCIATED WITH THIS COMPLEX SYSTEM WILL TRACK ACROSS
THE ALEUTIANS FROM WEST TO EAST...BRINGING WET AND GUSTY
CONDITIONS TO MUCH OF THE ALEUTIANS AND BERING THROUGH THURSDAY
EVENING. CONDITIONS WILL BECOME MORE SHOWERY OVER MUCH OF THE
BERING AND ALEUTIAN CHAIN THROUGH FRIDAY NIGHT...AS THE LOW
WEAKENS AND TRACKS EASTWARD.

AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...
SOUTHCENTRAL ALASKA...
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...
LONG TERM...