Winter Storm Warning 4, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
559 AM AKST THU JAN 15 2009

.DISCUSSION...THE LAST 2 DAYS WEATHER ARE AN EXCELLENT EXAMPLE OF
WHAT HAPPENS AS A BIG ALASKA COLD SNAP ENDS. THEY DO NOT EXIT
SUBTLY, BUT WITH STRENGTH AND FLOURISH. IN CONTRAST, WARM SPELLS
NORMALLY FADE WITHOUT ADO.

IN THIS CASE, A NUMBER OF SOUTHERN ALASKA INTERIOR SITES HAVE HAD
80 DEGREE RISES IN TEMPERATURE FROM 3 DAYS AGO TO NOW. THE CHINOOK
NOW FLOWING OVER/DOWN THE ALASKA RANGE INTO THE INTERIOR WILL BE
REINFORCED BY A SERIES OF FAST MOVING (ABOUT 50 KNOTS) WAVES ON THE
STRONG FRONT NOW RUNNING FROM KODIAK ISLAND TO ABOUT 35 DEGREES
NORTH 152 DEGREES WEST. NONE OF THE NUMERICAL GUIDANCE HAS DEFINED
THE DETAILS OF THESE STRONG INCOMING WAVES. THIS IS NORMAL FOR
SUCH HIGH ENERGY SYSTEMS, ESPECIALLY THOSE INBOUND TO ALASKA FROM
30-SOMETHING DEGREES NORTH.

THE FIRST FRONT IN THIS ONSLAUGHT IS NOW WEAKENING OVER THE
EASTERN GULF OF ALASKA COAST. ITS PARENT LOW IS NOW OVER SOUTHWEST
ALASKA AND WILL BE AN IMPORTANT FACTOR IN DEFINING SURFACE WINDS
OVER THE BERING SEA COAST OF ALASKA TODAY.

LOW #2 OF THIS SERIES IS NOT DEFINED BY THE NUMERICAL GUIDANCE.
SATELLITE IMAGERY SHOWS IT MOVING UP OVER KODIAK ISLAND AT THIS
TIME.

LOW #3 IS SOMEWHERE NEAR 35 DEGREES NORTH AND 153 DEGREES
WEST. THE NUMERICAL MODELS CALCULATE THAT THIS ONE WILL HAVE GREAT
ENERGY -- REACHING A CENTRAL PRESSURE OF 952 MB OVER KUSKOKWIM BAY
ON FRIDAY AFTERNOON. OUR FORECASTS HAVE TAKEN THIS SERIOUSLY AND
FULL GALES ARE EXPECTED FOR MUCH OF THE WEST COAST ON FRIDAY.
AFTER MOVING OVER KOTZEBUE FRIDAY NIGHT THIS LOW IS FORECAST TO
WEAKEN AND MOVE RAPIDLY INTO THE NORTHEAST BEAUFORT SEA ON
SATURDAY. FROM ALL PRESENT APPEARANCES, THIS LOW WILL BRING IN A
CLASSIC PINEAPPLE EXPRESS TO MUCH OF MAINLAND ALASKA ON FRIDAY AND
FRIDAY NIGHT.

TEMPERATURES OVERNIGHT HAVE RANGED FROM 10 BELOW ON THE YUKON
FLATS TO THE MID 50S ABOVE AT THE NORTH ENDS OF SOME ALASKA RANGE
PASSES. WHILE THE NORTH INTERIOR WILL CONTINUE TO WARM, ANOTHER
SURGE OF WARM AIR CAN EASILY BE EXPECTED FRIDAY AND FRIDAY
EVENING. AS IS NORMALLY THE CASE, ATMOSPHERIC CIRCULATION OVER
ALASKA IS FORECAST TO WEAKEN AFTER LOW #3 HAS RUN ITS COURSE.

ASIDE FROM THE UPPER TANANA VALLEY NEARLY ALL OF NORTHERN ALASKA
HAS SOME MODERATE TO STRONG IMPACT WEATHER. MOST OF THE
ADVISORIES, WATCHES AND WARNINGS NOW IN EFFECT WILL END BY
MIDNIGHT, AND WE EXPECT A NEW ROUND TO BEGIN FRIDAY AS THE FUTURE
PATH OF LOW #3 BECOMES BETTER DEFINED.

ANOTHER FEATURE NOT COVERED BY THE NUMERICAL MODELS IS A SMALL
SURFACE LOW OVER THE WESTERN BROOKS RANGE. EAST WINDS AND IFR
WEATHER NOW OVER THE ARCTIC COAST ARE FORECAST TO ABRUPTLY CHANGE
LATER TODAY AS THE WINDS SHIFT TO WEST SOUTHWEST AND THE IFR
WEATHER IMPROVED TO MVFR IN THE WEST TO VFR IN THE EAST.

THE VOLUME AND STRENGTH OF THE INCOMING WARM AIR ALOFT INTO THE
INTERIOR HAS BROUGHT PLENTY OF FREEZING RAIN AND SNOW TO THE WEST
AND NORTHERN INTERIOR, AS WELL AS TO THE SOUTH ENDS AND HIGH
POINTS OF ALASKA RANGE PASSES. MORE OF THIS IS FOR FRIDAY AND
FRIDAY NIGHT.

THE MEDIUM RANGE FORECAST ARE IN GENERAL AGREEMENT, FORECASTING A
BRIEF OUTBREAK OF WESTERLIES BELOW 65 DEGREES NORTH, FOLLOWED BY
WEAKER CIRCULATION ABOVE A GULF OF ALASKA RIDGE ALOFT THROUGH LATE
NEXT WEEK.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR AKZ222-AKZ223.

WINTER STORM WARNING FOR AKZ206-AKZ208-AKZ209-AKZ210-AKZ212-
AKZ215-AKZ216-AKZ217-AKZ218-AKZ219.

HIGH WIND WARNING FOR AKZ220-AKZ225-AKZ226.

BRISK WIND ADVISORY FOR PKZ200-PKZ210-PKZ220-PKZ225-PKZ230-
PKZ235-PKZ240-PKZ245.
&&

TF JAN 09