Heavy Snow in Alaska, September 27, 2015

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
141 AM AKDT SUN SEP 27 2015

.DISCUSSION...

A PROGRESSIVE AND ACTIVE WEATHER PATTERN WILL CONTINUE OVER THE
CWA DURING THE NEXT FEW DAYS.

UPPER AIR...
A SMOOTH TOPPED UPPER LEVEL RIDGE OVER THE WESTERN INTERIOR WILL
MOVE EASTWARD TO THE ALCAN BORDER BY LATE THIS AFTERNOON AND MOVE
ON EASTWARD INTO CANADA TONIGHT. A SHORT WAVE TROUGH CURRENTLY
EXTENDS FROM ABOUT 74N/175E IN THE RUSSIAN ARCTIC OCEAN SOUTHWARD
ACROSS EASTERN SIBERIA. THE TROUGH WILL MOVE EASTWARD TO NEAR THE
DATELINE BY LATE TONIGHT...AND TO THE CENTRAL ALASKA INTERIOR AND
SOUTHWARD BY LATE TUESDAY MORNING. AN UPPER LOW WILL DEVELOP ON
THE SOUTHERN PART OF THE TROUGH OVER THE NORTHEASTERN ALASKA
PENINSULA LATE MONDAY NIGHT...DEEPENING OVER THE PRINCE WILLIAM
SOUND AREA BY TUESDAY AFTERNOON.

WARMER AIR ALOFT WILL SPREAD EASTWARD ACROSS THE INTERIOR TODAY
IN SOUTHWEST FLOW BEHIND THE EXITING UPPER RIDGE AND AHEAD OF THE
INCOMING TROUGH. HIGH TEMPERATURES SOUTHERN INTERIOR AREAS AND
LOWER ELEVATIONS IN THE ALASKA RANGE ARE EXPECTED TO BE IN THE 40S
TO NEAR 50 TODAY...AND IN THE UPPER 40S TO LOWER 50S MONDAY. IN
THE NORTHERN INTERIOR...HIGH TEMPERATURES ARE EXPECTED TO BE IN
THE 30S TO NEAR 40 TODAY...AND MAINLY IN THE 40S TUESDAY. HIGH
TEMPERATURES IN THE BROOKS RANGE ARE EXPECTED TO BE NEAR OR BELOW
FREEZING TODAY...AND MAINLY IN THE 30S TO NEAR 40 OVER THE
SOUTHEASTERN BROOKS RANGE MONDAY. INTERIOR AND BROOKS RANGE
TEMPERATURES WILL BE COOLER TUESDAY AS THE INCOMING TROUGH BRINGS
IN A COLDER AIR MASS.

THE SHORT WAVE TROUGH IS EXPECTED TO SMOOTH OUT SOME AND EXIT
EASTWARD INTO CANADA WEDNESDAY...LEAVING BEHIND A COOL WEST TO
NORTHWEST FLOW OVER THE NORTHERN ALASKA MAINLAND. THE NEXT SHORT
WAVE RIDGE WILL ADVANCE EASTWARD...EXTENDING FROM THE CHUKOTSK
PENINSULA TO THE KODIAK ISLAND AREA BY THURSDAY AFTERNOON THEN
MOVING EASTWARD ACROSS THE MAINLAND THURSDAY NIGHT.

SURFACE...
A 992 MB LOW ABOUT 50 MILES NORTHWEST OF THE PRIBILOFS WILL MOVE
TO NEAR BETHEL BY 4 PM THIS AFTERNOON...DEEPENING TO AROUND 988
MB. BY 4 AM MONDAY THE LOW WILL DEEPEN TO A 985 MB LOW NEAR
HUSLIA. THE LOW WILL WEAKEN OVER THE CENTRAL BROOKS RANGE BY
MONDAY AFTERNOON AS A NEW 985 MB LOW DEVELOPS ABOUT 100 MILES
NORTH OF POINT THOMPSON. THE NEW LOW WILL DEEPEN TO A 978 MB
CENTER ABOUT 500 MILES NORTH OF POINT THOMPSON BY TUESDAY MORNING.

A NEW LOW WILL DEVELOP NEAR PRINCE WILLIAM SOUND BY MONDAY EVENING
IN ADVANCE OF THE DEEPENING SOUTHERN PART OF THE UPPER LEVEL
TROUGH. THIS LOW WILL DEEPENING OVER PRINCE WILLIAM SOUND THROUGH
TUESDAY MORNING...WITH A SECONDARY CENTER DEVELOPING SOUTHEAST OF
NORTHWAY TUESDAY MORNING...THEN MOVING NORTHEASTWARD INTO CANADA
TUESDAY NIGHT.

AS THE LOW NOW NEAR THE PRIBILOFS MOVES NORTHEAST...PRECIPITATION
WILL SPREAD NORTHWARD AND EASTWARD... COVERING MOST OF THE
SOUTHERN HALF OF NORTHERN ALASKA BY LATE THIS AFTERNOON. BY LATE
TONIGHT THE PRECIPITATION WILL SPREAD OVER MOST AREAS FROM THE
BROOKS RANGE SOUTHWARD AND PARTS OF THE INTERIOR ARCTIC SLOPE.
PRECIPITATION WILL CONTINUE OVER MOST OF THE CWA MONDAY... WITH
THE HEAVIEST AMOUNTS BEING OVER THE CENTRAL INTERIOR AND THE
CENTRAL/WESTERN ALASKA RANGE. THE PRECIPITATION TYPE IS EXPECTED
TO BE MAINLY SNOW FROM THE BROOKS RANGE NORTHWARD AND OVER THE
NORTHWEST INTERIOR...AND MAINLY RAIN SOUTH OF THE BROOKS RANGE.
OVER NORTHERN PARTS OF THE CENTRAL AND EASTERN INTERIOR NEAR THE
BROOKS RANGE...PRECIPITATION COULD BE RAIN...SNOW...OR MIXED. BY
LATE MONDAY NIGHT...THE PRECIPITATION TYPE WILL BE SNOW IN ALMOST
ALL AREAS AS COLDER AIR ALOFT MOVES IN FROM THE WEST.

IN AREAS WHERE SNOW IS EXPECTED...SNOWFALL AMOUNTS THROUGH TONIGHT
ARE EXPECTED TO REMAIN BELOW ADVISORY THRESHOLD. SNOW AMOUNTS OF
AROUND 3 INCHES ARE EXPECTED IN ZONE 217...2 TO 3 INCHES IN
WESTERN ZONE 218 AND SOUTHEASTERN ZONE 206 THROUGH TONIGHT. THERE
WILL BE POTENTIAL FOR SIGNIFICANT SNOWFALL IN ZONES 224 AND 226
TUESDAY AND TUESDAY NIGHT...THE LOW CENTER DEVELOPING SOUTHEAST OF
NORTHWAY THEN MOVING NORTHEAST WILL GENERATE SNOWFALL IN THESE
ZONES BEGINNING TUESDAY...NORTHWESTERLY LOW LEVEL WINDS WILL
PROVIDE SOME UPSLOPE AUGMENTATION OF SNOWFALL. SNOWFALL AMOUNTS OF
4 TO 8 INCHES WILL BE POSSIBLE IN THESE AREAS TUESDAY AND TUESDAY
NIGHT.

SOUTHERLY GAP WINDS ARE EXPECTED TO DEVELOP NEAR ALASKA RANGE
PASSES AND NEAR DELTA JUNCTION TODAY...CONTINUING THROUGH
EARLY MONDAY AFTERNOON IN ZONE 225...AND THROUGH MONDAY EVENING
IN ZONE 226 AND IN ZONE 223 NEAR DELTA JUNCTION. IN ZONE
225...GUSTS TO 60 MPH ARE EXPECTED AROUND 3 PM TODAY TO LATE
MONDAY MORNING. IN ZONE 226...GUSTS TO 60 MPH ARE EXPECTED FROM
AROUND MID AFTERNOON TODAY TO AROUND 6 PM MONDAY. IN ZONE 223...
GUSTS TO AROUND 50 MPH ARE EXPECTED DURING THE SAME TIME SPAN.
WINDS ACROSS THE ALASKA RANGE AT 700 AND 800 MB ARE PROGGED
TO MAX OUT AT 50 TO 60 KT.

COASTAL HAZARD POTENTIAL...
NORTH WINDS TO 25-35 MPH ARE EXPECTED SUNDAY NIGHT AND MONDAY
MORNING ON THE NORTHERN SEWARD PENINSULA COAST WEST OF CAPE
ESPENBERG. THIS COULD PRODUCE MODERATE SURF CONDITIONS. THE
DURATION AND LENGTH OF FETCH IS NOT EXPECTED TO BE LARGE ENOUGH TO
PRODUCE HEAVY SURF CONDITIONS. MAXIMUM WAVE HEIGHTS OFFSHORE NEAR
SHISHMAREF ARE EXPECTED TO BE AROUND 7 FEET.

&&

.HYDROLOGY...
RAINFALL AMOUNTS MAINLY FROM 0.75 TO 1.5 INCHES WILL BE
POSSIBLE IN ZONE 221...SOUTHERN ZONE 216...ZONE 227...AND ZONE
225 DURING THE 36 HOUR PERIOD ENDING AT 4 PM MONDAY. RAINFALL
AMOUNTS OF 0.5 TO 0.75 INCH COULD OCCUR IN ZONE 222 AND IN ZONE
215. SMALLER RAINFALL AMOUNTS ARE EXPECTED IN OTHER AREAS WHERE
RAIN IS EXPECTED. SNOWMELT AND NEW RAINFALL COULD RESULT IN
SIGNIFICANT RISES ON SOME RIVERS AND STREAMS.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR PKZ200-PKZ210-PKZ220.
WIND ADVISORY FOR AKZ223-AKZ225-AKZ226.

&&

RF SEP 15