Heavy Snow in Alaska, March 5 to 7, 2015

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
554 AM AKST THU MAR 5 2015

.DISCUSSION...
MODELS IN GOOD AGREEMENT IN THE SHORT TERM AS WELL AS THE MID TERM
BUT EXHIBIT EXPECTED SPREAD IN THE LONG TERM WITH TRANSITION FROM
STRONG PROGRESSIVE FLOW TO A BLOCKED PATTERN. PREFERRED THE ECMWF
ON ITS HANDLING OF THE DEVELOPMENT OF AND THE POSITION OF AN OMEGA
BLOCK OVER THE WESTERN BERING SEA BY MIDDLE OF NEXT WEEK. IN THE
SHORT TERM THE 00Z GFS...NAM AND ECMWF INITIALIZED WELL AGAINST
THE 06Z ANALYSIS. RELIED ON A BLEND OF ONGOING FORECAST PACKAGE
WITH AN EQUAL BLEND OF THE 00Z GFS AND ECMWF FOR TODAYS FORECAST
PACKAGE.

ALOFT AT 500 HPA...THE SHORTWAVE CURRENTLY POSITIONED ALONG THE
WEST COAST OF ALASKA WILL PUSH INTO THE WESTERN INTERIOR THIS
AFTERNOON AND EASTWARD TO NEAR FAIRBANKS BY FRIDAY MORNING. THE
SHORTWAVE EXITS INTO CANADA BY MID DAY FRIDAY AS A POWERFUL SHORT
WAVE TAKES AIM AT THE WEST COAST AND WESTERN INTERIOR. THE
NEGATIVELY TILTED TROUGH WITH AXIS STRETCHING FROM THE GULF OF
ANADYR TO ST PAUL ISLAND FRIDAY EVENING WILL PRESENT A FAVORABLE
UPPER LEVEL ENVIRONMENT FOR ADDITIONAL STRENGTHENING AS WELL AS
STRONG MID LEVEL MOISTURE TRANSPORT INTO THE EASTERN BERING SEA
AND WEST COAST OF ALASKA. UPPER LEVEL DIVERGENCE WILL FURTHER
ENHANCE SYNOPTIC LIFT OVER A WIDE AREA OF THE WEST COAST AND
WESTERN INTERIOR. AS A RESULT HAVE ISSUED WINTER STORM WATCHES FOR
HEAVY SNOW AND BLOWING SNOW OVER A LARGE AREA OF THE WEST COAST
AND WESTERN INTERIOR.

DEEP LAYER MOISTURE WILL COMBINE WITH FAVORABLE LIFTING ENVIRONMENT
AND HEFTY SNOW RATIOS IN THE 15 TO 20 TO 1 RANGE TO PRODUCE
WIDESPREAD HEAVY SNOW ON FRIDAY AND SATURDAY ON THE WEST COAST
AND SATURDAY AND SUNDAY IN THE WESTERN INTERIOR. WIDESPREAD STORM
TOTALS OF 6 TO 12 INCHES ARE LIKELY WITH HEAVIEST ACCUMULATIONS ON
FAVORED WEST AND SOUTHWEST UPSLOPE LOCATIONS SUCH AS THE NULATO
HILLS AND THE SOUTH FACING SLOPES OF THE SEWARD PENINSULA AND THE
SOUTH FACING SLOPES OF THE WESTERN BROOKS RANGE.  WILL NEED TO
MONITOR FOR HEADLINE POTENTIAL AS THIS SYSTEM MOVES INTO THE
WESTERN AND CENTRAL INTERIOR.

925 MB WINDS ARE PROGGED TO PUSH INTO THE 40 TO 50 KT RANGE ALONG
THE WEST COAST AND THE 30 TO 40 KTS RANGE OVER A LARGE AREA OF
THE WESTERN INTERIOR AND 20 TO 30 KTS IN THE CENTRAL INTERIOR.
STRONGEST WINDS OCCUR WITH WARM AIR ADVECTION AHEAD OF THE FRONT
AND THIS WILL LIMIT DAMAGING WIND GUST POTENTIAL ON THE SURFACE
HOWEVER BLOWING SNOW IS STILL EXPECTED TO REDUCE VISIBILITY OVER
OPEN TERRAIN AND WHERE RAIN DOES NOT MIX WITH THE SNOW. BEHIND THE
FRONT COLD AIR ADVECTION COMBINED WITH 925 MB WINDS IN THE 30 TO
40 KTS RANGE WILL KEEP THE WEST COAST BLUSTERY AND WILL LIKELY
REDUCE VISIBILITY IN BLOWING SNOW FOR A PERIOD AFTER THE HEAVY
SNOW DIMINISHES BEHIND THE FRONT.

A WEAK FRONT EXTENDING FROM NEAR PFYU SOUTHWEST TO NEAR PAMC WILL
BE THE FOCUS FOR PERIODS OF LIGHT SNOW TODAY WITH 1 TO 2 INCHES OF
SNOW EXPECTED IN THESE AREAS AND SCATTERED SNOW SHOWERS EXPECTED
ELSEWHERE AS THE FIRST SHORT WAVE PASSES FROM THE WESTERN INTERIOR
TO THE EASTERN INTERIOR. RELATIVELY QUITE ON THE NORTH SLOPE
TODAY AND THROUGH FRIDAY AS COMPARED TO RECENT BLIZZARDS ...EXPECTING
LIGHT WINDS WITH ONLY SCATTERED SNOW SHOWERS AND AREAS OF FOG.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FOR AKZ208-AKZ209-AKZ210-AKZ211-AKZ212-AKZ213-
AKZ214-AKZ215-AKZ216-AKZ217.

BRISK WIND ADVISORY FOR PKZ210.
&&

CCC MAR 15