Heavy Snow in Alaska, September 1, 2014

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
228 AM AKDT MON SEP 1 2014

.DISCUSSION...
SYNOPTIC SCALE MODELS CONTINUE TO BE IN GOOD AGREEMENT THROUGH THE
END OF THE WEEK BEFORE DEPARTING ON TRACK AND STRENGTH OF THE
UPPER LEVEL LOW OVER NORTH OF MAINLAND ALASKA. CURRENT WINTER
DEPTH 500 DAM LOW AT 500 HPA IS LOCATED 250 M NORTHWEST OF BARROW
WILL WOBBLE ON A CYCLONIC LOOPING TRAJECTORY TO BE ABOUT ABOUT 50
NM NORTH OF BARROW WEDNESDAY MORNING. THE UPPER LEVEL LOW THEN
MOVES RAPIDLY TO THE EAST TO BE 150 NM NORTH OF DEMARCATION POINT
WEDNESDAY EVENING AS A 516 DAM LOW.

A SERIES OF SHORT WAVES ROTATING AROUND THE UPPER LEVEL LOW WILL
SWEEP ACROSS NORTHERN ALASKA THROUGH THE WEEK. FOCUS CONTINUES TO
BE ON THE FIRST AND STRONGEST SHORT WAVE WHICH IS NOW PLOWING ITS
WAY INTO THE WESTERN ALASKA. A 996 MB WHICH IS CURRENTLY DEVELOPING
OVER NORTON SOUND WILL MOVE EASTWARD TO BE LOCATED NEAR PABT
MONDAY NIGHT AND PARC TUESDAY MORNING. A COLD FRONT SWEEPS THROUGH
THE INTERIOR AND STALLS EAST WEST ALONG THE ALASKA RANGE. STRONG
UPPER LEVEL DYNAMICS COMBINED WITH UPSLOPE ENHANCED UPSLOPE WILL
GENERATE HEAVY PRECIP OVER MUCH OF THE INTERIOR. BOTH THE ECMWF
AND THE GFS CONTINUE TO INDICATE STORM TOTAL PRECIP VALUES OF 1
INCH OR MORE FROM THE NULATO HILLS EAST TO THE KUSKOKWIM MOUNTAINS
IN WESTERN ALASKA AND 1 TO 2 INCH STORM TOTAL QPF VALUES IN THE
WESTERN ALASKA RANGE. SOME LOCATIONS IN THE WESTERN ALASKA RANGE
WILL LIKELY RECEIVE IN EXCESS OF 2 INCHES OF PRECIP. WIDESPREAD
SWATH STORM TOTAL RAIN FALL TOTALS OF 1 INCH OR MORE IS FORECAST
FROM THE NULATO HILLS EAST TO THE FAIRBANKS AREA AND ALONG THE
ALASKA RANGE. THE HEAVIEST RAIN WILL FALL FROM DENALI NATIONAL
PARK TO FAIRBANKS WHERE 1 TO 2 INCHES OF RAIN IS LIKELY. AGAIN
SOME LOCATIONS WILL RECEIVE OVER 2 INCHES. SNOW LEVELS WILL DROP
FOR AROUND 5000 FT TUESDAY MORNING TO AROUND 3000 FT TUESDAY
AFTERNOON AND CONTINUE TO DROP TUESDAY NIGHT. SIGNIFICANT ACCUMULATING
SNOW IS LIKELY TUESDAY NIGHT AND WEDNESDAY IN THE WESTERN ALASKA
RANGE. THOSE WITH OUTDOOR ACTIVITIES OR TRAVEL PLANS IN THE HIGH
COUNTRY SHOULD BE PREPARED FOR WINTER CONDITIONS.

SNOW LEVELS WILL DROP IN THE BROOKS RANGE FROM AROUND 3000 FT THIS
MORNING TO VALLEY LEVEL TUESDAY MORNING. SEVERAL INCHES OF SNOW
ARE LIKELY IN THE BROOKS RANGE. THOSE WITH OUTDOOR ACTIVITIES OR
TRAVEL PLANS IN THE BROOKS RANGE SHOULD BE PREPARED FOR WINTER
CONDITIONS.

STRONG 850 MB WINDS IN THE 45 KT TO 60KT RANGE ARE EXPECTED WITH
TO DEVELOP OVER THE CENTRAL INTERIOR AS THE SHORT WAVE APPROACHES.
WIND ADVISORIES ARE HOISTED FOR ZONES 221...222 AND 220 AS WIND
GUSTS TO 45 MPH ARE EXPECTED OVER INTERIOR HIGHWAY SUMMITS AND
HILLS.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...
SURGE MODELS INDICATE 2 TO 3 FOOT SURGE VALUES IN EASTERN NORTON
SOUND THOUGH MONDAY NIGHT WITH WAVE HEIGHTS OF AROUND 8 FEET WELL
OFF SHORE BUT CONSIDERABLY LOWER NEAR SHORE. ON SHORE WINDS ARE
EXPECTED TO BE AROUND 25 KTS...CONTINUE TO MONITOR FOR HIGH SURF.
SURGE MODELS INDICATE 1.5 FOOT SURGE ALONG THE NORTHWEST COAST
NEAR ICY CAPE AND AROUND 1 FOOT NEAR BARROW WITH 6 TO 8 FOOT WAVES
OFF SHORE TUESDAY. FETCH IS REASONABLE IN BOTH CASES HOWEVER WIND
DURATION AND MAGNITUDE WILL LIMIT HIGH SURF.

&&

.HYDROLOGY...
LOWERING FREEZING LEVELS WILL LIMIT FLASHY RESPONSE IN HIGHER
TERRAIN IN THE ALASKA RANGE SO NO SMALL STREAM ISSUES ARE EXPECTED
HOWEVER HYDRO MODELS CONTINUE TO INDICATE STREAMS AND RIVERS IN
THE MIDDLE TANANA VALLEY WILL LIKELY RISE TO ACTION STAGE BY
WEDNESDAY MORNING.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR AKZ220-AKZ221-AKZ222.

SMALL CRAFT ADVISORY FOR PKZ200-PKZ210-PKZ240-PKZ245.
&&

CCC SEP 14