Gale Warning 703, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
511 AM AKST SUN NOV 8 2015

.ANALYSIS AND UPPER LEVELS...
THE MAIN FEATURE ALOFT THIS MORNING IS A BIG BROAD UPPER LOW
CENTERED OVER THE NORTHWESTERN BERING SEA. A LARGE PLUME OF
MOISTURE IS EVIDENT ON WATER VAPOR SATELLITE WITH A SUB-TROPICAL
CONNECTION EXTENDING UP INTO THE SOUTHERN MAINLAND. A 140-KT JET
IS ROUNDING THE BASE OF THE TROUGH ACTING TO ADVECT MOISTURE ALOFT
AS WELL AS DEEPEN THE SYSTEM OVERALL OVER THE NORTHERN BERING SEA.
THE LARGE OCCLUDED FRONT STRETCHES FROM SAINT LAWRENCE ISLAND
SOUTHEASTWARD THROUGH THE SOUTHERN MAINLAND WHERE IT THEN BECOMES
A NARROW WARM FRONT/COLD FRONT. A STEADY RAIN SHIELD IS PUSHING
ASHORE WITH THE FRONT FROM THE KUSKOKWIM DELTA THROUGH INTERIOR
BRISTOL BAY. WIDESPREAD GALE TO STORM FORCE WINDS WRAP AROUND THE
SYSTEM. THE REMAINDER OF SOUTHCENTRAL IS BETWEEN THE DEPARTING
SYSTEM AND THE INCOMING ONE WITH GENERALLY QUIET WEATHER...ONLY
SOME PATCHY LOW CLOUDS WITH SOME STRONGER OUTFLOW WINDS ALONG THE
NORTH GULF COAST.

&&

.MODEL DISCUSSION...
THE FORECAST CHALLENGES FOR THE MODELS REMAIN BASICALLY THE SAME
AS YESTERDAY. THE LARGE SCALE SYNOPTIC PATTERN IS IN EVEN BETTER
AGREEMENT THAN YESTERDAY WITH THE LARGE BERING SEA PARENT LOW
PRESSURE. THE JET AND SHORTWAVE TROUGH TIMING/STRUCTURE ARE ALL
VERY SIMILAR AMONG MODELS...COMING INTO THE COOK INLET REGION LATE
TOMORROW EVENING. THE BIGGEST DIFFERENCES CONTINUE TO BE
TIMING/STRENGTH/TRACK OF THE TRIPLE POINT LOW...AND VARYING
DEGREES OF DOWNSLOPE DRYING. LIQUID PRECIPITATION AMOUNTS RANGE
FROM .1 INCHES TO .3 INCHES IN THE ANCHORAGE AREA. EVEN THOUGH
SOME DIFFERENCES ARE PRESENT...THERE IS GOOD AGREEMENT ON
BEGINNING PRECIPITATION IN ANCHORAGE BOWL IN THE MID-LATE EVENING
AND ENDING NOT LONG AFTER MIDNIGHT. WEST DOMAIN PREFERRED THE NAM
WHILE THE EAST PREFERRED THE GFS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE OVER SOUTH CENTRAL ALASKA WILL QUICKLY MOVE EAST
DURING THE DAY...WITH THE AXIS MOVING INTO THE YUKON THIS
AFTERNOON. A FRONT ASSOCIATED WITH A VERY LARGE BERING SEA CYCLONE
IS ALREADY MOVING INTO KODIAK ISLAND AND WILL PUSH INTO THE
MAINLAND THIS AFTERNOON AND EVENING. THIS FRONT IS QUITE OCCLUDED
BUT ALSO FAIRLY STRONG AND WILL BRING A BRIEF PERIOD OF HEAVY
PRECIPITATION TO MOST AREAS AS IT MOVES THROUGH. THIS PRECIP WILL
BE MAINLY IN THE FORM OF SNOW FOR INLAND AREAS...WITH RAIN ALONG
THE COASTAL AREAS AND NEAR KACHEMAK BAY. THIS FRONT WILL PUSH INTO
THE COPPER RIVER BASIN LATER TONIGHT AND THEN EAST OF THE AREA
MONDAY MORNING. WINDS ARE ALSO A BIT TRICKY WITH THIS SYSTEM AS A
TRIPLE POINT LOW WILL DEVELOP NEAR THE BARREN ISLANDS THIS
AFTERNOON...MOVE INTO PRINCE WILLIAM SOUND BY MIDNIGHT AND THEN
PUSH INLAND NEAR VALDEZ LATE TONIGHT. FOR MONDAY AND MONDAY NIGHT
SOUTH CENTRAL ALASKA WILL HAVE SOUTHWESTERLY CYCLONIC FLOW ALOFT
WHICH WILL BRING SCATTERED SHOWERS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

A STRENGTHENING AREA OF LOW PRESSURE LOCATED NEAR SAINT MATTHEW
ISLAND THIS MORNING WILL CONTINUE TO PUSH NORTHEASTWARD TOWARD
SAINT LAWRENCE ISLAND THIS EVENING. THIS WILL BRING INCREASINGLY
STRONG GUSTS TO THE WEST COAST OF ALASKA AS WELL AS HIGH SEAS AND
SURF. OBSERVATIONS (BOTH SURFACE AND UPPER AIR) THIS MORNING
CAPTURE THE WARM AIR ADVECTION ASSOCIATED WITH THE FRONT BEGINNING
TO IMPACT SOUTHWEST ALASKA. WITH TEMPERATURES IN THE MID 30S TO
LOWER 40S PRECIPITATION WILL CONTINUE TO FALL AS RAIN. THE FRONT
IS EXPECTED TO QUICKLY OCCLUDE OVER SOUTHWEST ALASKA THIS
AFTERNOON WHICH WILL HELP COLDER AIR TO ADVECT INLAND AND PRODUCE
A MORE FAVORABLE ENVIRONMENT FOR SNOW. BY TONIGHT...850 MB
TEMPERATURES WILL DROP TO -6 TO -8 DEGREES CELSIUS AND LIKELY ALL
PRECIPITATION WILL HAVE CHANGED OVER TO SNOW. THE STEADY
PRECIPITATION OBSERVED TODAY WILL BECOME MORE SHOWERY IN NATURE ON
MONDAY AS COLD AIR ADVECTION WILL CONTINUE TO FUEL THE DEVELOPMENT
OF PRECIPITATION UNDER THE BROAD UPPER LEVEL TROUGH. SNOW
ACCUMULATIONS ARE TOUGH TO PINPOINT DUE TO THE SHOWERY NATURE OF
PRECIPITATION BUT IT LOOKS LIKE 1 TO 3 INCHES OF SNOW SHOULD BE
FAIRLY COMMON THROUGH MONDAY WITH HIGHER AMOUNTS ALONG UPSLOPE
LOCATIONS. THERE HAS BEEN SOME CONCERN FOR BLOWING SNOW ALONG THE
COASTAL LOCATIONS BUT BECAUSE OF THE SHOWERY NATURE OF THE
SNOW...A PROLONGED PERIOD OF BLOWING SNOW CONDITIONS APPEARS VERY
UNLIKELY. THERE COULD BE BRIEF PERIODS WHERE VISIBILITIES DROP TO
1 MILE OR LESS BUT SHOULD GENERALLY PERSIST LESS THAN ONE HOUR.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

WIDESPREAD GALE AND STORM FORCE WINDS WILL BE COMMON ACROSS THE
BERING SEA OVER THE NEXT SEVERAL DAYS IN RESPONSE TO A
STRENGTHENING AREA OF LOW PRESSURE IN THE NORTHERN BERING SEA. A
STOUT WARM FRONT WILL PUSH ACROSS THE EASTERN ALEUTIANS AND ALASKA
PENINSULA THIS MORNING AND BRING SOME LOCALIZED WIND GUSTS OF
60 TO 65 MPH THROUGH CHANNELED TERRAIN. COLD AIR WILL QUICKLY
FILTER IN BEHIND THIS FRONT AS IT OCCLUDES OVER SOUTHWEST
ALASKA...WHICH IS EVIDENT BY LOOKING AT TEMPERATURE TRACES OVER
SHEMYA...ADAK AND ATKA. THIS COLD AIR ADVECTION WILL NOT ONLY
CONTINUE TO PRODUCE WIDESPREAD RAIN AND SNOW SHOWERS...BUT ALSO
CREATE A REMOTE POSSIBILITY OF ISOLATED THUNDERSTORMS ACROSS THE
BERING SEA THROUGH TONIGHT. THE COLD AIR ADVECTION WILL STEEPEN
THE LOW LEVEL LAPSE RATES AND INTERACT WITH SOME SURFACE-BASED
INSTABILITY. THIS SHOULD GENERALLY ACT TO ENHANCE LOCAL
RAINFALL/SNOWFALL RATES BUT WITH ENOUGH INSTABILITY A FEW
LIGHTNING STRIKES CANNOT BE RULED OUT. GUSTY WINDS AND RAIN/SNOW
SHOWERS WILL CONTINUE INTO THE MIDDLE OF NEXT WEEK UNDER THE BROAD
TROUGH THAT ENCOMPASSES THE BERING SEA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

THE OVERWHELMING FORECAST CONCERN FOR THE MID- TO LATE-WEEK
PERIOD IS THE GROWING LIKELIHOOD OF A LOW PRESSURE SYSTEM TO
UNDERGO EXPLOSIVE CYCLOGENESIS (A.K.A. BOMBOGENESIS) AS IT TREKS
QUICKLY ALONG THE GREAT CIRCLE ROUTE FROM THE WESTERN ALEUTIANS
TUESDAY ACROSS THE SOUTHERN BERING WEDNESDAY AND INTO THE GULF OF
ALASKA LATE WEEK. THIS LOW HAS THE POTENTIAL TO BRING POWERFUL
HURRICANE-FORCE WINDS OUT OF THE NORTH AND WEST TO THE FAR SOUTH-
CENTRAL BERING SEA AND CENTRAL ALEUTIANS EAST THROUGH THE EASTERN
ALEUTIANS AND THE ALASKA PENINSULA AND ADJACENT WATERS. THE GFS
AND EC MODELS NOW AGREE ON THE GENERAL PLACEMENT...TRACK...AND
INTENSITY OF THIS LOW...WITH THE CANADIAN MODEL ONLY SLIGHTLY
FASTER.

AS A RESULT OF THIS BETTER MODEL AGREEMENT...THE GRIDDED AND TEXT
FORECASTS WILL NOW SHOW A SIGNIFICANT INCREASE IN WINDS TO IMPACT
THESE AREAS DURING THIS TIME...BUT WILL REMAIN FOR THIS MORNING'S FORECAST
PACKAGE A BIT BELOW THE FULL STRENGTH AS DEPICTED BY THE GFS
MODEL. HIGH WIND WATCHES AND POSSIBLY WARNINGS MAY BE NEED TO BE
ISSUED FOR THE CENTRAL AND EASTERN ALEUTIANS EAST THROUGH THE
ALASKA PENINSULA IF CURRENT TRENDS HOLD AND/OR CONTINUE FOR LATE
TUESDAY INTO EARLY THURSDAY. THOSE WITH INTERESTS IN OR NEAR
ADAK...ATKA...DUTCH HARBOR/UNALASKA...FALSE PASS...COLD BAY...KING
COVE...AND SAND POINT SHOULD CHECK BACK FREQUENTLY FOR FURTHER
DETAILS ON THE POTENTIAL FOR THIS SYSTEM TO BRING SIGNIFICANT
IMPACTS AS WE APPROACH MID-WEEK.

OTHERWISE...ONSHORE FLOW AND SHOWER ACTIVITY OVER THE SOUTHERN MAINLAND
WILL GIVE WAY TO INCREASINGLY OFFSHORE FLOW BY THE END OF THE WEEK
AS THE AFOREMENTIONED BERING LOW WEAKENS (YET STILL REMAINS QUITE
STRONG) IN THE CENTRAL GULF. THIS WILL ALLOW FOR THE COLDEST AIR
MASS OF THIS WINTER SEASON TO BUILD SOUTH INTO THE SOUTHERN
MAINLAND...COLDEST IN THE COPPER RIVER BASIN. STRONG OFFSHORE
WINDS THROUGH TERRAIN GAPS MAY ALSO BECOME POSSIBLE ALONG THE
NORTH GULF COAST DURING THIS TIME.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING...145
 		 WINTER WEATHER ADVISORY...101 111
		 HIGH SURF ADVISORY...155.
MARINE...GALES...119 120 125 131 132 138 150 155 160 165 170
				 172-178 180.
		 STORMS...179 181 185.

&&

SYNOPSIS AND MODEL DISCUSSION...MTL
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...CC