Area Forecast Discussion
Issued by NWS Anchorage, AK

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
000
FXAK68 PAFC 141347
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
447 AM AKST SUN FEB 14 2016

.ANALYSIS AND UPPER LEVELS...

A WEAKENING VERTICALLY STACKED LOW CENTERED OVER THE EASTERN
ALEUTIANS IS THE PRIMARY DRIVER OF THE WEATHER PATTERN OVER
SOUTHERN ALASKA THIS MORNING. THE LOW IS DIGGING A TROUGH INTO THE
SUBTROPICAL JET SOUTH OF IT...ALLOWING RIDGES TO BUILD EAST AND
WEST OF IT. THE RIDGE WEST OF THE TROUGH OVER THE NORTHWEST
PACIFIC WILL ALLOW FOR THE JET TO ENCROACH OVER THE WESTERN
BERING...WHICH HELPS TO KEEP THE PATTERN ACTIVE IN THE VICINITY OF
THE JET. IT MAY ALSO HELP TO FINALLY ALLOW FOR SOME PROGRESSION
IN THE WEATHER PATTERN...EVEN IF BRIEFLY.

AN UPPER LEVEL TROUGH EXTENDING EASTWARD FROM THE UPPER LOW OVER
THE EASTERN BERING IS COLLOCATED WITH A SURFACE LOW MOVING OVER
MARMOT BAY. THIS LOW CONTINUES TO DRAW COPIOUS GULF MOISTURE
NORTHWESTWARD INTO PRINCE WILLIAM SOUND...EASTERN KENAI
PENINSULA...AND KODIAK ISLAND. IN ADDITION...NORTHEAST WINDS
DOWNSLOPING OFF THE TALKEETNAS...CHUGACH...AND KENAI MOUNTAINS
BEING DRAWN TOWARDS THE LOW ARE KEEPING CONDITIONS VERY MILD
ACROSS MUCH OF SOUTHCENTRAL...FOLLOWING A PATTERN THAT HAS BEEN
INCREDIBLY PERSISTENT THIS WINTER. ANCHORAGE HAD ITS WARMEST DAY
OF 2016 SO FAR YESTERDAY AS A RESULT. ANCHORAGE`S SOUNDING SHOWS
THAT OTHER THAN A SHALLOW LAYER OF NORTHEAST WINDS NEAR THE
SURFACE...ABOVE THAT THE WINDS THROUGH THE MID-LEVELS ARE BROAD
SOUTHEASTERLY...WHICH ARE KEEPING THE ATMOSPHERE RELATIVELY WARM.

GENERALLY LIGHT NORTHEAST FLOW AHEAD OF THE LOW NEAR KODIAK IS
KEEPING CONDITIONS LARGELY DRY OVER MUCH OF SOUTHWEST ALASKA AS
DRY AIR FROM THE INTERIOR MAKES ITS WAY TOWARDS THE COAST. DESPITE
THIS...MIDDLE AND UPPER LEVEL CLOUD COVER IS PLENTIFUL AS MOISTURE
CLEARS THE ALEUTIAN MOUNTAINS AND OVERSPREADS SOUTHWEST ALASKA.
LOCALIZED SHOWER ACTIVITY IS SUCCESSFULLY CLEARING THE ALEUTIAN
MOUNTAINS OVER THE ALASKA PENINSULA AS THE FLOW THERE IS LESS
CROSS-BARRIER.

OVER THE BERING...SHOWER ACTIVITY IS PLENTIFUL. BETWEEN THE
VERTICALLY STACKED LOW OVER THE EASTERN BERING...THE ENCROACHING
SUBTROPICAL JET OVER THE WESTERN BERING AND ALEUTIANS...AND
EMBEDDED SMALLER DISTURBANCES ROTATING AROUND AND IN BETWEEN
THEM...CLOUD COVER AND ASSOCIATED SHOWERS WILL HAVE NO TROUBLE
PERSISTING THROUGH THE DAY AREA-WIDE. FORTUNATELY SINCE NONE OF
THESE FEATURES ARE PARTICULARLY STRONG...THE WINDS ARE GENERALLY
LIGHT BERING SEA-WIDE.

&&

.MODEL DISCUSSION...

THE MODELS INITIATED IN DECENT AGREEMENT SHOWING THE PRIMARY
FEATURES AFFECTING SOUTHERN ALASKA AND THE BERING. DISCREPANCIES
BETWEEN THEM ARISE REGARDING THE DEVELOPMENT OF A STRONG LOW IN
THE FAR WESTERN BERING ALONG THE KAMCHATKA PENINSULA. FOR THE PAST
FEW DAYS NOW...THE GFS HAS BEEN THE MOST CONSISTENT AND PERSISTENT
OF THE MODELS BRINGING A STRONG FRONT ASSOCIATED WITH THAT LOW
ACROSS THE BERING. THE EC HAS BEEN THE OUTLIER...FLIP-FLOPPING
AROUND THE GFS POSITION. IN THE LATEST RUNS...THE EC HAS COME INTO
BETTER AGREEMENT WITH THE GFS. FOR LOCAL EFFECTS...THE CANADIAN
HAS BEEN THE MOST CONSISTENT...AND WAS THE MODEL OF CHOICE.
FORECAST CONFIDENCE IS NORMAL.

ON THE EAST SIDE...THERE ARE FEW FEATURES OF NOTE EXPECTED OVER
THE NEXT TWO DAYS FOR THE MODELS TO DISAGREE ON. THE LOW OVER
KODIAK ISLAND IS UNANIMOUSLY AGREED UPON TO MOVE INTO THE
NORTHERN ALASKA PENINSULA TODAY. OUTSIDE OF THAT...A NORTH
PACIFIC LOW IS FORECAST TO TRACK WELL SOUTH OF THE WESTERN GULF
MONDAY NIGHT AND INTO THE SOUTHERN PANHANDLE SOMETIME TUESDAY.
WHILE THERE ARE SOME MODEL DISAGREEMENTS ON THE DETAILS OF THAT
LOW...NONE OF THOSE DISCREPANCIES HAVE ANY IMPACT ON THE WEATHER
IN SOUTHCENTRAL OR THE GULF.

&&

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

THE UPPER LEVEL WAVE AND SURFACE LOW ARE MOVING ONSHORE FROM THE
GULF TO THE WESTERN PRINCE WILLIAM SOUND AREA. THIS IS CAUSING
THIS MORNING`S GOES SATELLITE IMAGERY AND THE RADAR LOOKS ALMOST
IDENTICAL TO THIS TIME YESTERDAY. THERE ARE SOME DIFFERENCES FROM
YESTERDAY WITH THE FIRST BEING THAT THERE WILL BE LESS PRESSURE
RISES BEHIND THIS WAVE AND THEREFORE LESS SOUTHERLY WINDS WITH
THIS SYSTEM. THE ATMOSPHERE REMAINS UNSEASONABLY WARM RESULTING
IN MOST OF THE PRECIPITATION BEING IN THE FORM OF RAIN AT SEA
LEVEL. AFTER THIS WAVE THERE WILL BE A TRANSITION TO MORE
NORTHERLY FLOW ON MONDAY WHICH WILL RESULT PARTIAL CLEARING OVER
SOUTHCENTRAL TUESDAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAKENING LOW OVER KODIAK WILL CROSS THE ALASKA PENINSULA WHILE
WEAKENING TODAY...WHICH WILL KEEP INTERMITTENT LIGHT RAIN AND
SNOW SHOWERS ACROSS BRISTOL BAY AND ISOLATED TO SCATTERED SNOW
SHOWERS ACROSS THE KUSKOKWIM DELTA AND LOWER KUSKOKWIM VALLEY.
SHOWERS WILL BEGIN TO DIMINISH MONDAY AS HIGH PRESSURE BUILDS
OVER SOUTHWEST.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
WEAK LOW PRESSURE OVER THE BERING WILL SUPPORT RAIN AND SNOW
SHOWERS ACROSS THE REGION THROUGH THIS AFTERNOON...BEFORE HIGHER
PRESSURE SETTLES IN AND A SLOW DRYING TREND DEVELOPS. A STRONG
GALE-FORCE LOW AND ASSOCIATED FRONT WILL ENTER THE WESTERN BERING
MONDAY MORNING...BRINGING WET AND WINDY CONDITIONS TO THE AREA.
THIS SYSTEM WILL RAPIDLY PROGRESS EASTWARD INTO THE CENTRAL
ALEUTIANS/BERING MONDAY NIGHT...THEN BEGIN TO SPREAD WET AND WINDY
CONDITIONS INTO THE EASTERN ALEUTIANS BY TUESDAY MORNING.

&&

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

...FROM PREVIOUS DISCUSSION...

A DRY PERIOD IS ON TAP FOR THE EARLY PORTION OF THE EXTENDED
FORECAST AS A RIDGE OF HIGH PRESSURE BUILDS OVER ALASKA. THIS IS
IN RESPONSE TO A PATTERN CHANGE IN WHICH THE STORM TRACK IS TAKING
A MORE NORTHERLY PATH. THE STRONG UPPER LOW NEAR THE KAMCHATKA
PENINSULA WILL DRIVE THE STORM SYSTEM IN THE CENTRAL BERING AND
ALEUTIANS EASTWARD MONDAY THROUGH TUESDAY. THE LEADING FRONT WITH
THIS SYSTEM WILL REACH THE SOUTHWEST MAINLAND TUESDAY
NIGHT...BRINGING SOME PRECIPITATION TO THAT AREA BUT NOT INTO
SOUTHCENTRAL. THIS SYSTEM WILL THEN SPLIT AS IT HITS THE ALASKAN
RIDGE. MOST OF THE ENERGY WILL DIVE SOUTH INTO THE GULF OF ALASKA
BY THURSDAY. AT THE SAME TIME THE KAMCHATKA LOW WILL BREAK INTO
TWO LOWS...WITH ONE OF THESE MOVING INTO THE ALEUTIANS. ALL OF
THIS WILL DRIVE THE MAIN STORM TRACK FURTHER SOUTH AGAIN. THE
EXTENDED GUIDANCE IS BASED HEAVILY ON THE ECMWF AND ITS ENSEMBLE
MEAN EARLY...THEN ON A BLEND OF ENSEMBLE MEANS LATER ON.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...130 139 178
 HEAVY FREEZING SPRAY...185

&&

$$

SYNOPSIS AND MODEL DISCUSSION...ML
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP
LONG TERM...BL


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.