821
FXAK69 PAFG 190102
AFDAFG
NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
402 PM AKST MON NOV 18 2024
SYNOPSIS
AN ACTIVE AND HIGHLY AMPLIFIED WEATHER PATTERN BRINGS HAZARDOUS
WEATHER -PARTICULARLY BLIZZARD CONDITIONS- TONIGHT THROUGH TUESDAY
NIGHT. AS A RESULT, NUMEROUS ADVISORIES AND WARNINGS ARE IN
EFFECT ACROSS NORTHERN ALASKA BETWEEN MIDNIGHT TONIGHT AND
WEDNESDAY AFTERNOON. A STRONG WARM FRONT EXTENDING EAST FROM A
STORM IN SIBERIA LIFTS NORTHEAST ALONG THE WEST COAST LATE
TONIGHT, BRINGING A PERIOD OF BLIZZARD CONDITIONS. FOR THE NORTH
SLOPE, UNSEASONABLY STRONG WINDS FROM AN UNUSUAL DIRECTION
(SOUTHWEST) WITH A LONGER TERRESTRIAL FETCH AND DOWNSLOPING OFF
THE BROOKS RANGE INCREASING THE CHANCE OF BLIZZARD CONDITIONS
ABOVE WHAT WIND SPEED ALONE WOULD INDICATE. SEVERAL ADVISORIES
ALONG THE NORTH SLOPE WERE UPGRADED TO WARNINGS ACCORDINGLY. SOUTH
OF THE WARM FRONT ALONG THE WEST COAST, A PROLONGED PERIOD OF
FREEZING DRIZZLE IS POSSIBLE STARTING TUESDAY MORNING THEN
CONTINUING INTO WEDNESDAY AFTERNOON. FREEZING DRIZZLE POTENTIAL
EXTENDS FARTHER INLAND
-INCLUDING FAIRBANKS- BUT THE START/END TIMES WILL BE DELAYED
BY12-24 HOURS. IN ADDITION TO LIGHT ICING ASSOCIATED WITH
FREEZING DRIZZLE, BREEZY WINDS DRAINING COLD AIR THROUGH
ISABEL/WINDY PASSES AND THE TANANA/YUKON VALLEY JETS RESULT IN A
VARIETY OF WIND AND WINTER WEATHER ADVISORIES ACROSS THE
INTERIOR.
KEY MESSAGES
CENTRAL AND EASTERN INTERIOR...
- MODERATE NORTH WINDS EXPECTED ON THE SOUTH SIDE OF THE ALASKA
THROUGH TONIGHT OF BLOWING SNOW, REDUCING VISIBILITY TO ONE HALF
MILE OR LESS AT TIMES, A WINTER WEATHER ADVISORY REMAINS IN
EFFECT THROUGH TONIGHT.
- THERE IS A SLIGHT CHANCE OF FREEZING DRIZZLE ON WEDNESDAY ACROSS
THE TANANA VALLEY, HOWEVER, FORECAST UNCERTAINTY REMAINS HIGH ON
IF PRECIPITATION WILL REACH THE SURFACE. WIDESPREAD IMPACTS ARE
NOT EXPECTED AT THIS TIME.
- SOUTHEAST WINDS AT EAGLE WILL GUST TO 40 MPH WITH WIND CHILLS
AS LOW AS 45 BELOW ZERO, A WIND ADVISORY REMAINS IN EFFECT
TUESDAY NIGHT THROUGH THURSDAY.
NORTH SLOPE AND BROOKS RANGE...
- MULTIPLE BLIZZARD WARNINGS HAVE BEEN ISSUED FOR THE NORTH
CENTRAL BROOKS RANGE OVER TO THE NW ARCTIC COAST WITH WIND GUSTS
UP TO 75 MPH, SNOW ACCUMULATIONS UP TO 7 INCHES, AND BLOWING
SNOW. WINDS WILL GRADUALLY DIMINISH WEDNESDAY MORNING BUT
SNOWFALL IS EXPECTED TO CONTINUE.
- WINTER STORM WARNINGS HAVE BEEN ISSUED FOR THE NOATAK VALLEY
AND LOWER KOBUK VALLEY WITH SNOW ACCUMULATIONS UP TO 10 INCHES,
ICE ACCUMULATIONS UP TO A LIGHT GLAZE, WIND GUSTS UP TO 50MPH,
AND BLOWING SNOW.
-HIGH WIND WARNING HAS BEEN ISSUED FOR THE CENTRAL BROOK RANGE,
PRIMARILY FOR ANAKTUVUK PASS WITH SUSTAINED WINDS UP TO 40MPH AND
WINDS GUSTS UP TO 65MPH EXPECTED TUESDAY MORNING THROUGH
WEDNESDAY MORNING.
WEST COAST AND WESTERN INTERIOR...
- MULTIPLE BLIZZARD WARNINGS REMAIN IN EFFECT FROM POINT
HOPE SOUTHWARD TO KOTZEBUE SOUND TO THE BERING STRAIT COAST
MONDAY NIGHT INTO WEDNESDAY WITH WIND GUSTS UP TO 55 MPH, SNOW
ACCUMULATIONS UP TO 6 INCHES, AND BLOWING SNOW. MAIN CONCERN
WILL BE A BRIEF PERIOD OF FREEZING RAIN RESULTING IN A LIGHT ICE
GLAZE ALONG THE BERING STRAIT AND SEWARD PENINSULA COAST ON
TUESDAY AND WEDNESDAY.
- A HIGH SURF ADVISORY REMAINS IN EFFECT FROM KIVALINA AND RED
DOG WITH MINOR COASTAL EROSION EXPECTED WITH WATER LEVELS
REACHING UP TO 2 TO 4FT ABOVE THE NORMAL HIGH TIDE LINE STARTING
TUESDAY NIGHT INTO WEDNESDAY.
- FOR THE WESTERN INTERIOR AND YUKON DELTA, MULTIPLE WINTER
WEATHER ADVISORIES HAVE BEEN ISSUED WITH SNOW ACCUMULATIONS UP
TO 4 INCHES, ICE ACCUMULATIONS OF A LIGHT GLAZE AND WIND GUSTS
UP TO 45 MPH.
DISCUSSION
SURFACE RIDGING AT ABOUT 1032+MB DOMINATES THE SURFACE PATTERN
ACROSS NORTHERN ALASKA WITH THE RIDGE CENTERED OVER THE CENTRAL
ALEUTIANS (+3 STANDARD DEVIATIONS ABOVE CLIMATOLOGY). SATELLITE
IMAGERY SHOWS STRATUS LINGERING OVER THE UPPER TANANA AND YUKON
VALLEYS WITH A SECONDARY AREA OF CLOUDINESS ACROSS THE NORTH
SLOPE. CLOUDS CONTINUE TO DIMINISH AS RIDGING BUILDS ACROSS THE
AREA TONIGHT, RESULTING IN A VERY COLD NIGHT WITH LOWS DIPPING
INTO THE - 25F TO -35F RANGE FOR INTERIOR VALLEYS. NORTHERLY WINDS
THROUGH THE BROOKS/ALASKA RANGE PASSES COMBINED WITH VERY COLD
TEMPERATURES CAUSES WIND CHILLS TO APPROACH COLD WEATHER ADVISORY
CRITERIA. AS RIDGING SHIFTS EAST AND THE UPSTREAM LOW PRESSURE
MOVES OVER THE CHUKCHI SEA THE SURFACE PRESSURE PATTERN FAVORS
DEVELOPMENT OF THE TANANA AND YUKON VALLEY JETS RESULTING IN
BLOWING SNOW AND COLD WIND CHILLS.
THE PRIMARY FEATURE OF INTEREST CONTINUES TO BE A SEASONABLY
STRONG LOW PRESSURE (-3 STANDARD DEVIATIONS BELOW CLIMATOLOGY)
SPINNING UP OVER THE NORTHERN CHUKCHI SEA ON TUESDAY. THIS HIGHLY
AMPLIFIED PATTERN RESULTS IN A CORRIDOR OF STRONG SOUTHERLY FLOW
ADVECTING A MUCH WARMER AND MOISTURE LADEN AIR MASS ACROSS OUR
AREA. MIMIC TPW IMAGERY ALREADY SHOWS THIS NARROW CORRIDOR OF
WARM/MOIST AIR STREAMING NORTH (LIKELY IMMEDIATELY AHEAD OF THE
COLD FRONT) JUST TO THE EAST OF THE KAMCHATKA PENINSULA. FARTHER
EAST, THE WARM FRONT CAN BE SEEN LIFTING NORTHEAST ACROSS THE
BERING SEA. THIS WARM FRONT SURGES NORTHEAST OVER THE NEXT 24-36
HOURS BRINGING THE MOST WIDESPREAD PERIOD OF IMPACTFUL WEATHER.
FOR THE WEST COAST, MODEL SOUNDINGS SUGGEST THIS FROPA WILL BE
CHARACTERIZED BY A 6-9 HOUR BURST OF SNOWFALL ACCOMPANIED BY
RAPIDLY INCREASING WINDS AND ASSOCIATED BLOWING SNOW. THE
STRONGEST WINDS WILL BE WITHIN 12 HOURS OF THE WIND SHIFT AND EVEN
THOUGH SOUTHERLY WINDS DIMINISH SOUTH OF THE FRONT ON TUESDAY,
THEY'LL STILL BE STRONG ENOUGH TO LOWER VISIBILITY WITHIN BLOWING
SNOW. FOR THE NORTH SLOPE AND ARCTIC COAST, THIS PERIOD OF SNOW
AND WIND APPEARS PARTICULARLY UNUSUAL/IMPACTFUL FOR TWO REASONS.
THE FIRST BEING POTENTIAL FOR EXTREME SNOWFALL AND THE SECOND IS
THE STRONG WINDS WILL BE FROM AN UNUSUAL SOUTHWESTERLY DIRECTION.
DIGGING DEEPER INTO THE EXTREME SNOWFALL, 2-DAY SNOWFALL AMOUNTS
EXCEEDING 6 INCHES WOULD RANK IN THE TOP 25 SNOWFALLS FOR THEIR
123 YEAR PERIOD OF RECORD. SOUTHWESTERLY FLOW DOWNSLOPING OFF THE
BROOKS RANGE (SHIFT OF TAILS > 2) MAY RESULT IN AN UNUSUALLY LONG
FETCH FOR BLOWING SNOW AND THE UNUSUAL DIRECTION IMPLIES A
SUBSTANTIAL AMOUNT OF PREVIOUSLY DRIFTED SNOW WILL BECOME
BLOWABLE. NAEFS GUIDANCE HIGHLIGHTS INTEGRATED VAPOR TRANSPORT
VALUES >13 STANDARD DEVIATIONS ABOVE CLIMO POINTED DIRECTLY AT
UTQIAGVIK TUESDAY NIGHT. THIS INCREDIBLE MOISTURE TRANSPORT
COMBINED WITH POTENTIAL FOR THE TRIPLE POINT TO PASS NEAR
UTQIAGVIK PERHAPS SUSTAINING POTENTIAL FOR HEAVIER SNOWFALL RATES,
IT SEEMED PRUDENT TO UPGRADE ALL HEADLINES TO BLIZZARD WARNINGS
ACROSS THE WESTERN NORTH SLOPE. ONE COMPLICATING FACTOR IS THE
POTENTIAL FOR SURFACE TEMPERATURES WARMING SLIGHTLY ABOVE FREEZING
RESULTING IN WETTER SNOWFLAKE CHARACTERISTICS THAT MAY BE
DIFFICULT TO BLOW. HOWEVER, WITH TEMPS ONLY BARELY SQUEAKING ABOVE
FREEZING THIS ASPECT MAY BE NEGATED BY THE AMOUNT OF SNOWFALL ON
TOP OF SNOW ON THE GROUND.
THE NEXT FEATURE OF INTEREST IS THE SYSTEMS COLD FRONT DROPPING
SOUTH ACROSS THE NORTH SLOPE ON WEDNESDAY THEN INTO THE INTERIOR
WEDNESDAY NIGHT AND THURSDAY, BUT SUBSTANTIAL MODEL DIFFERENCES
EXIST. FREEZING DRIZZLE MAY BE PERSISTENT FOR AREAS FAVORED BY
WEST OR SOUTHWEST UPSLOPE FLOW INTO THE INTERIOR, WHICH MAY BE
PARTICULARLY IMPACTFUL FOR THE DALTON HIGHWAY SUMMITS. THIS
POTENTIAL IS SUPPORTED BY MODEL SOUNDINGS SHOWING SHALLOW
SATURATION UP TO AROUND 5KFT BENEATH AN UPPER LEVEL DRY SLOT
AMIDST VEERING LOW LEVEL FLOW. THE SATURATED LAYER BEING PRIMARILY
WARMER THAN -12C (DGZ) IMPLIES LITTLE IF ANY CLOUD ICE AND A
CLASSIC ENVIRONMENT FOR FREEZING DRIZZLE, BUT IT MAY MIX WITH SNOW
PELLETS AT TIMES IF CLOUD ICE IS INTRODUCED.
COASTAL HAZARD POTENTIAL...
STRONG SOUTHWEST TO WEST WINDS DEVELOP TONIGHT INTO TOMORROW AND
PERSIST INTO WEDNESDAY FROM POINT HOPE EAST TO UTQIAGVIK. THESE
WINDS WILL RESULT IN THE POTENTIAL FOR ELEVATED WATER AND BEACH
EROSION ALONG THE COAST, MAINLY NORTH OF THE BERING STRAIT. HIGH
SURF ADVISORIES ARE IN EFFECT FOR PORTIONS OF THE KOTZEBUE SOUND.
EXTENDED FORECAST FOR DAYS 4 THROUGH 7...
THE HIGHLY AMPLIFIED PATTERN LOOKS TO CONTINUE AND BRING MORE
ACTIVE WEATHER TO THE AREA. A STRONG UPPER LEVEL RIDGE WILL
DOMINATE FRIDAY AND SATURDAY BEFORE A SHORTWAVE WILL ATTEMPT TO
WEAKEN THE RIDGE FROM THE NORTHWEST ON SUNDAY. MODELS DIVERGE
THEREAFTER, BUT GENERALLY INDICATE CONTINUED RIDGING WHICH WILL
BRING STRONG INVERSIONS TO THE INTERIOR. MINOR PERTURBATIONS
WORKING THROUGH THE ZONAL FLOW WILL RESULT IN SCATTERED PERIODS OF
PRECIPITATION, PARTICULARLY FOR THE NORTH SLOPE AND WEST COASTAL
ALASKA.
AFG WATCHES/WARNINGS/ADVISORIES
AK...BLIZZARD WARNING FOR AKZ801-815-817-820-821.
BLIZZARD WARNING FOR AKZ802-803.
WINTER WEATHER ADVISORY FOR AKZ848-850.
WINTER STORM WARNING FOR AKZ814-816.
HIGH SURF ADVISORY FOR AKZ815.
WINTER WEATHER ADVISORY FOR AKZ818-823>826.
WINTER WEATHER ADVISORY FOR AKZ819-828>830.
WINTER WEATHER ADVISORY FOR AKZ822.
WINTER WEATHER ADVISORY FOR AKZ804.
WIND ADVISORY FOR AKZ835.
BLIZZARD WARNING FOR AKZ805.
WINTER STORM WARNING FOR AKZ806-807.
HIGH WIND WARNING FOR AKZ809.
PK...SMALL CRAFT ADVISORY FOR PKZ801-802-852.
HEAVY FREEZING SPRAY WARNING FOR PKZ802.
BRISK WIND ADVISORY FOR PKZ803.
BRISK WIND ADVISORY FOR PKZ804.
BRISK WIND ADVISORY FOR PKZ805.
HEAVY FREEZING SPRAY WARNING FOR PKZ806.
GALE WARNING FOR PKZ806-807-854-856.
HEAVY FREEZING SPRAY WARNING FOR PKZ807.
GALE WARNING FOR PKZ808.
GALE WARNING FOR PKZ809.
STORM WARNING FOR PKZ810.
STORM WARNING FOR PKZ811.
GALE WARNING FOR PKZ812.
BRISK WIND ADVISORY FOR PKZ813.
BRISK WIND ADVISORY FOR PKZ814-860-861.
BRISK WIND ADVISORY FOR PKZ815.
SMALL CRAFT ADVISORY FOR PKZ816.
GALE WARNING FOR PKZ817.
SMALL CRAFT ADVISORY FOR PKZ850-853.
GALE WARNING FOR PKZ851.
HEAVY FREEZING SPRAY WARNING FOR PKZ852.
HEAVY FREEZING SPRAY WARNING FOR PKZ853.
GALE WARNING FOR PKZ855.
HEAVY FREEZING SPRAY WARNING FOR PKZ856.
HEAVY FREEZING SPRAY WARNING FOR PKZ857.
STORM WARNING FOR PKZ857.
GALE WARNING FOR PKZ858.
BRISK WIND ADVISORY FOR PKZ859.
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