High Surf Advisory 6, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
554 AM AKDT WED SEP 9 2015

.DISCUSSION...

MAIN FORECAST HIGHLIGHTS INCLUDE SNOW AND BLOWING SNOW IN THE
BROOKS RANGE...THE LOW POTENTIAL FOR THUNDERSTORMS IN THE
INTERIOR AND CHINOOK WINDS IN THE ALASKA RANGE PASSES AND NEAR
DELTA JUNCTION.

09/00Z DETERMINISTIC MODELS ARE GOOD AGREEMENT THROUGH THE FIRST
60 HOURS REGARDING THE OVERALL LARGE SCALE PATTERN...HIGH PRESSURE
OVER THE HIGH ARCTIC AND EASTERN RUSSIA AND A LONGWAVE TROUGH OVER
MAINLAND ALASKA THROUGH THE REST OF THE WEEK. THERE ARE MINOR
DIFFERENCES AMONGST THE MODELS REGARDING STRENGTH AND POSITION OF
LOW CENTERS WITHIN THE LONGWAVE TROUGH. INCREASED SPREAD IN MODEL
SOLUTIONS AS WE PROGRESS INTO THE WEEKEND...AS MODELS ATTEMPT TO
HANDLE THE REMNANTS OF KILO AND JIMENA...LEADING TO A LOW
CONFIDENCE IN THE FORECAST DURING THE MID TO LONG TERM.

ALOFT...LONGWAVE TROUGH CONTINUES TO BE THE DOMINANT FEATURE OVER
MAINLAND ALASKA. THE BROAD 536 DAM CENTER NEAR UNALASKA THIS
MORNING WILL DIG SOUTHWARD AND STRENGTHEN TO A 525 DAM LOW CENTER
NEAR PILOT POINT LATE WEDNESDAY EVENING...THEN ROTATE NORTHEAST TO
NEAR KING SALMON THURSDAY AFTERNOON. A WEAK SHORTWAVE/VORT MAX
WILL MOVE OVER THE SOUTHERN INTERIOR THIS EVENING. ANOTHER
SHORTWAVE OFF THE WESTERN ARCTIC COAST WILL MOVE INLAND
TODAY...THEN STALL AND WEAKEN ALONG THE BROOKS RANGE TONIGHT.
ANOTHER LOW CENTER WILL DEVELOP OVER POINT LAY THURSDAY MORNING
AND MOVE SOUTH TO OVER SEWARD PENINSULA BY FRIDAY MORNING. THERE
IS SOME MODEL DISAGREEMENT REGARDING THE MOVEMENT AND PROGRESSION
OF THESE TWO LOW CENTERS. MEANWHILE...THE LONGWAVE TROUGH
ENCOMPASSING THESE TWO LOW CENTERS WILL GRADUALLY SHIFT EAST
THROUGH THE REST OF THE WEEK...KEEPING MAINLAND ALASKA UNDER THE
INFLUENCE OF THIS TROUGH.

SURFACE...LOOSELY DEFINED TROUGH STRETCHING FROM NEAR MACKENZIE
BAY SOUTHWEST OVER SOUTHWEST ALASKA AND ENCOMPASSING THE ALEUTIAN
ISLANDS THIS MORNING. A DEVELOPING 995 MB LOW PRESSURE 275 MILE
SOUTHEAST OF UNALASKA WITH ROTATE NORTHEAST AND STRENGTHEN INTO A
979 MB LOW NEAR PILOT POINT BY THIS EVENING. THIS LOW CONTINUE ITS
TREK NORTHEAST AND OVER INTERIOR ALASKA THURSDAY AND
FRIDAY...WEAKENING AS IT DOES INTO A BROAD 995 MB LOW OVER
INTERIOR ALASKA BY LATE FRIDAY MORNING. A 1000 MB LOW 100 MILE
NORTH OF POINT HOPE WILL MOVE OVER KOTZEBUE SOUND THIS MORNING AND
EVENTUALLY MERGE WITH THE BROAD SURFACE TROUGH THIS AFTERNOON.
HIGH PRESSURE OVER THE ARCTIC OCEAN AND THE CHUKOTSK PENINSULA WILL
GRADUALLY SHIFT EAST. A MODERATE PRESSURE GRADIENT WILL REDEVELOP
OVER THE CHUKCHI SEA...BERING STRAIT AND NORTHERN BERING SEA THIS
AFTERNOON...ALLOWING NORTH TO NORTHEAST WINDS TO INCREASE ONCE
AGAIN OVER MARINE ZONES ALONG THE WEST COAST.

NORTH SLOPE...THE MAIN ISSUE WILL BE SNOW AND BLOWING SNOW IN THE
CENTRAL AND EASTERN BROOKS RANGE OVER THE NEXT FEW DAYS. PERIODS
OF SNOW WILL BE LIKELY OVER THE HIGHER ELEVATIONS OF THE BROOKS
RANGE THROUGH THURSDAY AFTERNOON...WITH UP 3 TO 6 INCHES POSSIBLE
ALONG THE CENTRAL AND EASTERN BROOKS RANGE. BLOWING SNOW IN BROOKS
RANGE PASSES...MAINLY ATIGUN PASS AND ANAKTUVUK PASS WILL BE POSSIBLE
AS GUSTS UP 25 MPH ARE EXPECTED. REDUCTIONS IN VISIBILITY ARE NOT
EXPECTED SINCE THE LOFT POTENTIAL OF THE SNOW WILL BE LOW GIVEN
THE WET CHARACTERISTIC OF THE SNOW. ADDITIONALLY...KAKTOVIK/BARTER
ISLAND WILL SEE A FEW INCHES OF SNOW. WINDS WILL PICK UP ALONG
THE EASTERN BEAUFORT SEA COAST TO BETWEEN 30 TO 35 KTS THURSDAY
AND FRIDAY...BUT NOT EXPECTING ANY PROBLEMS WITH REDUCED
VISIBILITIES IN BLOWING SNOW SINCE TEMPERATURES WILL BE IN THE
LOWER TO MID 30S AND EXPECTING SOME RAIN TO MIX IN AT TIMES WITH
THE SNOW THURSDAY AND FRIDAY. WINDS WILL ALSO INCREASE
TONIGHT...FOR NUIQSUT AND DEADHORSE WITH GUSTS CLOSE TO 40 MPH BY
FRIDAY. OTHERWISE...A CHANCE FOR SNOW AND RAIN AND AREAS OF FOG
FROM BARROW EAST INCLUDING THE COASTAL PLAINS OF ZONES 205 AND 206
THROUGH FRIDAY.

WESTERN ALASKA...WINDS WILL BE THE MAIN ISSUE ALONG THE WEST
COAST. THE PRESSURE GRADIENT WILL INCREASE AGAIN TODAY AND TONIGHT
OVER THE CHUKCHI SEA COAST...SOUTHEAST TO THE BERING STRAIT...AND
OVER SAINT LAWRENCE ISLAND. WINDS WILL INCREASE THROUGHOUT THE DAY
TODAY TO BETWEEN 20 TO 35 MPH WITH GUSTS TO 45 AND WILL PERSIST
THROUGH THURSDAY NIGHT BEFORE WEAKENING. DENSE FOG HAS BEEN
REPORTED AT SEVERAL LOCATIONS IN ZONES 214...215 AND 227 AND THUS
HAVE HEADLINED DENSE FOG IN THE ZONES THROUGH NOON.
OTHERWISE...ISOLATED TO SCATTERED RAIN SHOWERS TODAY...THEN
ISOLATED TO SCATTERED RAIN SHOWERS MAINLY SOUTH OF THE SEWARD
PENINSULA. AS COOLER TEMPERATURES SOUTH AND THEN EAST OVER THE
WESTERN INTERIOR...MAY SEE SOME SNOW MIXING IN WITH RAIN THURSDAY
OVER HIGHER ELEVATIONS...AND THEN MIXING WITH SNOW NORTH OF THE
SEWARD PENINSULA THURSDAY NIGHT AND FRIDAY.

CENTRAL AND EASTERN INTERIOR...THE QUESTION OF THE DAY IS WHETHER
OR NOT WE SEE ISOLATED THUNDERSTORMS DEVELOP OVER THE INTERIOR
THIS AFTERNOON AND EVENING. MODELS ARE HINTING THAT WE MAY SEE
ONE...GIVEN THAT THE GFS IS PAINTING 200 TO 300 J/KG OF CAPE WITH
SLIGHTLY NEGATIVE LI VALUES STRETCHING FROM LAKE MINCHUMINA
NORTHEAST OVER THE HILLS NORTH OF FAIRBANKS AND INTO ZONE 220.
THIS COUPLED WITH FAVORABLE DYNAMICS...WE MAY SEE A FEW LIGHTNING
STRIKES. THERE IS THE LOW CHANCE FOR AN ISOLATED THUNDERSTORM
AGAIN THURSDAY AFTERNOON AND EVENING.

SOUTHERLY FLOW ALOFT WILL HELP SUPPORT A WEAK CHINOOK IN THE
ALASKA RANGE WITH SOUTH WINDS 25 TO 35 MPH WITH GUSTS TO 45 MPH IN
PASSES AS WELL AS NEAR DELTA JUNCTION THROUGH THURSDAY NIGHT AND
THEN WEAKEN. THIS WILL KEEP THE SOUTHERN INTERIOR DRY AND
PRECIPITATION FREE THROUGH FRIDAY MORNING. A WEAK SHORTWAVE IN THE
FLOW WILL TRAVERSE THE SOUTHERN INTERIOR LATE THIS AFTERNOON AND
EVENING...WHICH MAY BRIEFLY SHIFT THE WINDS TO THE WEST...ENOUGH
SO THAT A FEW SHOWERS MAY DEVELOP IN THE FAIRBANKS AREA. RAIN AND
SNOW ARE LIKELY ON THE SOUTHERN SLOPES OF THE EASTERN BROOKS
RANGE. TEMPERATURES WILL BE A BIT WARM FOR JUST SNOW...SO NOT
EXPECTING ANY SNOW ACCUMULATION. WILL HAVE A FEW MORE WARM DAYS
ACROSS THE SOUTHERN INTERIOR DUE TO THE WEAK CHINOOK...BUT ONCE IT
IS OVER...TEMPERATURES WILL COOL TO BELOW NORMAL VALUES FOR THE
WEEKEND AND EARLY NEXT WEEK.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE

&&

.HYDROLOGY...NO CONCERNS AT THIS TIME.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR PKZ200-PKZ210-PKZ215-PKZ220-PKZ225-
PKZ230.

GALE WARNING FOR PKZ210-PKZ220.

&&

LTH SEP 15