Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 051432
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
532 AM AKST FRI FEB 5 2016

.ANALYSIS AND UPPER LEVELS...

THE LARGE SCALE REGIONAL/HEMISPHERIC PATTERN REMAINS VERY MUCH
THE SAME THIS MORNING. IT IS CHARACTERIZED BY A POWERFUL NORTH
PACIFIC JET STREAM...A STOUT NORTH AMERICAN RIDGE OVER THE WEST
COAST...AND A BROAD ALEUTIAN LOW CENTERED OVER THE EASTERN
ALEUTIANS. REGIONS OF COLD ARCTIC AIR REMAIN OVER EASTERN SIBERIA
AND NORTHERN CANADA...WITH WARM WEDGES OF AIR CONTINUING TO PUMMEL
SOUTHERN ALASKA AS POWERFUL LOWS UNDERGO RAPID CYCLOGENESIS ALONG
THE NORTH PAC JET BEFORE MOVING INTO THE GULF. ANOTHER ONE OF
THESE FORMERLY STORM-FORCE LOWS IS RAPIDLY WEAKENING AS IT MOVES
INTO SOUTHWEST ALASKA THIS MORNING. THE COLDEST AIR OF THE REGION
REMAINS OVER THE WESTERN BERING AND ALEUTIANS AS A LOW LEVEL
NORTHERLY FLOW KEEPS A SUPPLY OF SIBERIAN ARCTIC AIR OVER THE
AREA.

RADAR DEPICTS A RATHER BROAD REGION OF WIDESPREAD SHOWERS
IMPACTING THE GULF COAST IN SOUTHEAST FLOW...WITH MORE STRATIFORM
RAIN AND SNOW ACROSS SOUTHWEST ALASKA IN CONJUNCTION WITH A
WEAKENING SURFACE LOW CENTERED OVER COLD BAY. WITH TIME...THE
GENERAL FLOW OVER SOUTHERN ALASKA WILL SHIFT TO A SOUTHWEST
ONSHORE FLOW...BRINGING INCREASED PRECIPITATION CHANCES TO INLAND
LOCATIONS TODAY AND TONIGHT.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN EXCELLENT AGREEMENT WITH THE LARGE SCALE
PATTERN DEEP INTO NEXT WEEK. THEY ARE IN OVERALL GOOD AGREEMENT
WITH A DEEP LOW MOVING INTO THE GULF OF ALASKA SATURDAY NIGHT AND
SUNDAY...AND IN DECENT AGREEMENT WITH ANOTHER DEEP STORM-FORCE
LOW MOVING TOWARD THE WESTERN BERING AND ALEUTIANS SUNDAY AND
SUNDAY NIGHT. WHERE THEY ARE STRUGGLING IS WITH SMALLER SCALE
FRONTS AND LOWS MOVING INTO SOUTHERN ALASKA TODAY AND TONIGHT.
SOME UNCERTAINTY EXISTS WITH A FRONT WHICH WILL MOVE UP COOK INLET
TODAY. THE MODELS DIFFER ON TIMING AND ORIENTATION...WHICH WILL
IMPACT THE POTENTIAL FOR SNOW ALL ALONG THE KENAI PENINSULA NEAR
COOK INLET UP INTO ANCHORAGE AND THE MATANUSKA VALLEY. WHILE
BRIEF...THE FRONT IS EXPECTED TO BE MOVING INTO POPULATED AREAS
THIS AFTERNOON AND EVENING...POTENTIALLY IMPACTING RUSH HOUR
TRAFFIC. WHILE BRIEF AND SHORT LIVED...THIS MAY RESULT IN PERIOD
OF BRIEF MODERATE SNOW WITH LIGHT ACCUMULATIONS. ALL THE MODELS
HAVE SLIGHTLY DIFFERENT DEPICTIONS...SO A BLEND OF ALL OF THEM WAS
INCORPORATED INTO THE NEAR TERM FORECAST. THEREAFTER...A GENERAL
BLEND TO THE ECMWF AND GFS WAS FAVORED.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE WEATHER FRONT THAT IS DEVELOPING SOUTH OF THE KENAI PENINSULA
WILL CONTINUE TO CONSOLIDATE TODAY AND MOVE NORTH. THIS SYSTEM WILL
SLIDE ACROSS THE KENAI PENINSULA THIS MORNING THROUGH THE
AFTERNOON. IT WILL REACH THE ANCHORAGE AREA AND MATANUSKA/SUSITNA
VALLEYS THIS AFTERNOON. THERE IS ENOUGH DYNAMICS AND COLD AIR WITH
THIS SYSTEM TO POSSIBLY PRODUCE SOME ACCUMULATING SNOWFALL.
LIMITING FACTORS ARE THE INITIAL WARM TEMPERATURES AND THE FACT
THAT THE FRONT IS MOVING RATHER FAST. THIS FRONT WILL MOVE WELL
INLAND TONIGHT AND BREAK APART. AN UPPER LEVEL VORT-MAX WILL PUSH
INTO KODIAK ISLAND FROM THE SOUTH THIS AFTERNOON THEN INTO THE
SOUTH CENTRAL MAINLAND TONIGHT THROUGH EARLY SATURDAY AFTERNOON.
IT WILL THEN BREAK APART WELL INLAND LATE SATURDAY AFTERNOON. THE
ASSOCIATED SURFACE LOW WILL TRAIL THE VORT-MAX THE ENTIRE
TIME...MOVING ONSHORE NEAR SEWARD AROUND NOON SATURDAY. ON
SATURDAY NIGHT AN UPPER LEVEL RIDGE WILL BUILD OVER SOUTH CENTRAL
ALASKA IN RESPONSE TO A LARGE LOW APPROACHING THE GULF FROM THE
SOUTH. THE LEADING FRONT WITH THIS LOW WILL BE NEARING THE NORTH
GULF COAST BY LATE SATURDAY NIGHT.

&&

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

A DISTURBANCE CURRENTLY IMPACTING BRISTOL BAY WILL CONTINUE TO
BRING AREAS OF LIGHT SNOW TO THE REGION THROUGH THIS AFTERNOON AS
IT TRACKS TOWARD THE BERING...BRINGING AN INCH OR LESS OF
ACCUMULATING SNOW. A BETTER CHANCE OF WIDESPREAD SNOW DEVELOPS AS
COLDER AIR MOVES NORTH AND EAST ACROSS SOUTHWEST ALASKA TONIGHT
INTO EARLY SATURDAY...WITH UP TO A COUPLE OF INCHES OF LIGHT SNOW
ESPECIALLY FOR INLAND KUSKOKWIM DELTA SOUTH AND EAST THROUGH THE
BRISTOL BAY ZONE. PARTIAL CLEARING OCCURS BEHIND THIS SYSTEM
ESPECIALLY FROM BRISTOL BAY NORTH THROUGH THE KUSKOKWIM VALLEY
ZONE SATURDAY AFTERNOON THROUGH SATURDAY NIGHT...ALLOWING
TEMPERATURES TO DROP A BIT CLOSER TO SEASONAL NORMALS. SCATTERED
SNOW SHOWER ACTIVITY AND CLOUD COVER WILL LINGER LONGER INTO
SATURDAY NIGHT TOWARD THE KUSKOKWIM DELTA.

&&

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

ACTIVE WEATHER CONTINUES TO IMPACT THE ISLAND AREAS AND PENINSULA
OF THE BERING REGION. SNOW AND BLOWING SNOW CONDITIONS OVER THE
FAR WESTERN ALEUTIANS WITH VISIBILITY RESTRICTIONS FREQUENTLY
BELOW A MILE WILL DIMINISH TO SHOWER ACTIVITY AS COLD ADVECTION
KICKS IN BY THIS AFTERNOON. ANOTHER LOW PRESSURE SYSTEM NEAR THE
CENTRAL ALEUTIANS WILL BRING A CHANGE IN WINDS FROM SOUTHWEST TO
NORTHWEST AND A PERIOD OF WET SNOW AND RAIN TO THE CENTRAL
ALEUTIANS BEFORE ALSO DIMINISHING TO SCATTERED SHOWER ACTIVITY
DURING THE WEEKEND. ANOTHER SMALL LOW MOVES NORTH ACROSS THE
EASTERN ALEUTIANS BY TONIGHT AND WILL BRING RAIN AND SNOW WITH
LITTLE SNOW ACCUMULATIONS. THIS SYSTEM WILL WEAKEN AS IT MOVES
NORTH TOWARD THE PRIBILOFS THROUGH SATURDAY. MEANWHILE...THE
SYSTEM NEAR THE AKPEN LIFTS NORTH AND EAST INTO BRISTOL
BAY...LEAVING MUCH QUIETER WEATHER CONDITIONS FOR LATE SATURDAY
INTO EARLY SUNDAY BEFORE THE NEXT SYSTEM APPROACHES FROM THE SOUTH
SUNDAY AND BEYOND.

&&

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

AS MENTIONED ABOVE...THE NEXT LOW THAT MOVES INTO THE GULF OF AK OVER
THE WEEKEND WILL PUSH A RELATIVELY STRONG FRONT INTO THE COAST SUN
MORNING. THIS FRONT WILL LOOK VERY SIMILAR TO MANY OF THOSE WE
HAVE SEEN OVER THE PAST FEW WEEKS WITH A NORTHEAST TO SOUTHWEST
ORIENTATION. WE DID INCREASE THE WINDS ALONG IT TO MAXIMUM GALES
WITH THE MORNING PACKAGE. IF MODELS CONTINUE TO TREND
STRONGER...CANNOT RULE OUT THE POTENTIAL FOR YET ANOTHER STORM
FORCE FRONT ALONG THE COAST.

A MID LEVEL LOW CENTERED OVER EASTERN RUSSIA CONTINUES TO STAY
ANCHORED WITH A LONG WAVE TROUGH EXTENDING TOWARD THE WESTERN GULF
OF ALASKA THROUGH THE LONG TERM FORECAST. A RIDGE TO THE EAST OF
THIS FEATURE WILL HAVE AN AXIS OVER BRITISH COLUMBIA. MODELS ARE
IN GOOD AGREEMENT WITH THE PATTERN...HOWEVER TIMING AND STRENGTH
DIFFERENCES FOR TWO CLOSED LOWS JUST SOUTH OF THE ALASKA PENINSULA
LEAD TO UNCERTAINTY IN PRECIPITATION AND WINDS FOR THE BEGINNING
OF NEXT WEEK. THIS GENERAL PATTERN KEEPS A WARMER THAN NORMAL
TEMPERATURE TREND THROUGH THE END OF NEXT WEEK WITH THE HIGHEST
PRECIPITATION CHANCES ACROSS THE AREA WATERS AND COASTS AS RIDGING
SHIFTS SLIGHTLY WEST AND AMPLIFIES OVER SOUTHERN ALASKA DURING THE
MIDDLE OF NEXT WEEK.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNINGS 132 150 155 170 172 176 177 178.
         HEAVY FREEZING SPRAY...185.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...JA
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CC
LONG TERM...KH/MSO


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