Brisk Wind Advisory 179, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
558 AM AKST SUN DEC 9 2012

.DISCUSSION...
YESTERDAYS COMPUTER WEATHER FORECAST MODELS PEGGED THE MAJOR
DEVELOPMENTS WELL...BOTH THE HEAVY WINDS OVER THE BERING STRAIT
AND SAINT LAWRENCE ISLAND WATERS...AND THE WIDESPREAD SNOWFALL NOW
SPREADING OVER THE INTERIOR.

THE GFS AND NAM COMPUTER WEATHER FORECAST MODELS ARE ALSO IN
AGREEMENT ON THE NEXT LOW PRESSURE SYSTEM TO AFFECT THE REALM.
THIS LOW IS FORECAST TO MOVE OVER THE SOUTHERN BERING SEA ON
TUESDAY AND TO REACH THE YUKON DELTA WEDNESDAY MORNING. THIS
SYSTEM CONTINUES TO LOOK LIKE IT WILL BRING SUBSTANTIAL SNOWFALL
TO THE WEST COAST ZONES SOUTH OF KOTZEBUE ON WEDNESDAY...AND TO
MUCH OF THE INTERIOR /..WITH THE EXCEPTION OF THE EASTERN ALASKA
RANGE AND THE FORTYMILE COUNTRY../ WEDNESDAY NIGHT AND THURSDAY.

TEMPERATURES ARE RISING NEARLY EVERYWHERE IN THE
REALM...ESPECIALLY IN THE INTERIOR...WHERE A MODERATE COLD SNAP OF
NEARLY THREE WEEKS IN DURATION HAS DECISIVELY ENDED. TEMPERATURES
HAVE COME UP AS MUCH AS 30 DEGREES AT SOME SOUTHEASTERN INTERIOR
STATIONS. A CHINOOK WIND OVER THE ALASKA RANGE IS NOT
EXPECTED...SO THE RISE IN TEMPERATURES IN THE INTERIOR WILL BE
MODEST. THIS IS CONSISTENT WITH A FORECAST OF EXTENSIVE SNOW. IN
THE INTERIOR...AN ALASKA RANGE CHINOOK AND WIDESPREAD SNOWFALL ARE
INCOMPATIBLE.

AS THE NAM AND GFS MODELS HAD FORECAST ON SATURDAY EVENINGS
RUNS...THE NORTHERLY GALES FROM POINT HOPE SOUTH TO THE SAINT
LAWRENCE ISLAND WATERS REACHED MAXIMUM STRENGTH AROUND
MIDNIGHT...AND ARE NOW VERY GRADUALLY DIMINISHING. THE SAINT
LAWRENCE ISLAND STORM YESTERDAY THROUGH THIS MORNING IS SIMILAR TO
ONE TWO YEARS AGO. ALL OF THE INGREDIENTS ARE PRESENT...

1. A STRONG NORTH WIND FROM BERING STRAIT TO SAINT LAWRENCE ISLAND

2. PLENTY OF OPEN WATER /FROM SHORE TO ABOUT 50 MILES
NORTH...WHICH IS UPWIND

3. COLD TEMPERATURES /NEAR 10 ABOVE ON SAINT LAWRENCE ISLAND
TODAY/

4. DEW POINTS 5 ABOVE OR LOWER.

COLD DRY AIR IS IDEAL FOR SPRAY. AIR TEMPERATURES AROUND 25
DEGREES F COLDER THAN THE SEA SURFACE CREATE A VERY UNSTABLE
BOUNDARY LAYER...WHICH IS CONDUCIVE TO A HIGH GUST FACTOR AS WELL
AS UPDRAFTS WHICH LOFT SEA SPRAY. THE LOWER THE RELATIVE
HUMIDITY...THE FASTER SEA SPRAY FREEZES DUE TO EVAPORATIVE
COOLING.

THE ONLY DIFFERENCE BETWEEN THE PRESENT SAINT LAWRENCE ISLAND
STORM AND THE ONE 2 YEARS AGO IS THAT THERE WAS MORE OPEN WATER TO
THE NORTH OF THE ISLAND IN 2010...AND POSSIBLY STRONGER WINDS.

THIS MORNINGS POLAR ORBITTING SATELLITE IMAGERY SHOWS LAYERED
FRONTAL CLOUDS OVER ALL THE REALM SOUTH OF TELLER TO OLD CROW. THE
NORTH SLOPE OF THE BROOKS RANGE IS THE COLDEST PART OF NORTHERN
ALASKA...WITH TEMPERATURES IN MOST PLACES FROM 20 BELOW TO 40
BELOW.

THE BRISK EAST WINDS AT BIG DELTA REACHED A PEAK SPEED NEAR 45 MPH
OVERNIGHT. THE REPORTED DEPTH OF SNOW ON THE GROUND THERE IS ONLY
A TRACE...SO THE RESTRICTION TO VISIBILITY BEING REPORTED MAY BE
DUE TO BLOWING DUST.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING FOR AKZ213.

HEAVY FREEZING SPRAY WARNING FOR PKZ210.

GALE WARNING FOR PKZ210-PKZ220-PKZ225.

BRISK WIND ADVISORY FOR PKZ200-PKZ240-PKZ245.
&&

TF DEC 12