Snow Advisory 5, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
614 AM AST TUE DEC 6 2005

.DISCUSSION...

...ACTIVE WEATHER PATTERN WILL CONTINUE THROUGHOUT THE WEEK
BRINGING WARMER TEMPERATURES AND FREQUENT BOUTS OF SNOW TO MUCH OF
NORTHERN ALASKA...

ALOFT...A NORTHWEST-SOUTHEAST ORIENTED RIDGE DOMINATES THE 500 MB
PATTERN OVER NORTHERN ALASKA. A 500 MB LOW IS LOCATED OVER THE
WESTERN ALEUTIANS. BETWEEN THESE TWO FEATURES DISTURBANCES
CONTINUE TO RIDE FROM SOUTH TO NORTH BRINGING MUCH WARMER AND
MOISTER AIR INTO THE REGION. THE 500 MB LOW OVER THE WESTERN
ALEUTIANS WILL STRENGTHEN AND SLOWLY SLIDE NORTHEASTWARD WITH
TIME. THE NET EFFECT OF THIS EVOLUTION WILL BE TO BACK THE WINDS
FROM SOUTHWESTERLY TO MORE SOUTHERLY WHICH WILL LEAD TO INCREASED
DOWNSLOPE EFFECTS NORTH OF THE ALASKA RANGE.

SURFACE...SURFACE PATTERN A NEAR CARBON-COPY OF YESTERDAY WITH
DISTURBANCES RIDING NORTHWARD INTO OUR SOUTHWESTERN ZONES. THESE
DISTURBANCES ARE PIN-WHEELING AROUND THE PRIMARY 975 MB LOW
CENTERED OVER THE WESTERN ALEUTIANS. A NEW LOW PRESSURE IS
DEVELOPING SOUTH OF THIS PRIMARY CENTER AND WILL BECOME THE
DOMINANT SYSTEM IN THE REGION BY LATER TODAY. IT WILL DEEPEN TO
NEAR 950 MB AS IT PASSES NORTHWEST OF COLD BAY AND INTO BRISTOL
BAY. HIGH PRESSURE CONTINUES TO DOMINATE THE SURFACE PATTERN IN
EASTERN RUSSIA AND WESTERN CANADA.

MODELS...THE GFS AND ETA INITIALIZED REASONABLY WELL WITH THE ETA
BEING TOO WEAK WITH THE SYSTEM OVER THE ALEUTIANS AND THE GFS
HAVING TROUBLE RESOLVING THE STRENGTH OF THE HIGH PRESSURE CENTER
OVER EASTERN RUSSIA.

NORTH SLOPE...CLEAR AND COLD CONDITIONS DOMINATE EVERYWHERE EXCEPT
THE NORTHERN PORTION OF ZONE 201 AND MOST OF ZONE 202 WHERE SOME
LOW STRATUS AND VERY LIGHT SNOW CONTINUE TO PERSIST. HIGH CLOUDS
WILL BEGIN TO OVERRUN THE REGION LATER THIS MORNING AND BY
OVERNIGHT TONIGHT SOME LIGHT SNOW WILL BEGIN TO MOVE INTO ZONES 205
AND 206 FROM THE SOUTH. AS LOW PRESSURE DEEPENS OVER BRISTOL BAY
NORTHEASTERLY WINDS WILL FRESHEN AND WILL BLOW AROUND ANY SNOW
THAT DOES FALL.

WEST COAST...CLOUDS HAVE SPREAD OVER MUCH OF THE WEST COAST WITH
THE EXCEPTION OF THE NORTHERNMOST ZONES. IN ADDITION SNOWFALL HAS
MOVED AS FAR NORTH AS ZONES 212 AND 216 WITH NORTHWESTWARD MOVING
BANDS OF SNOW NOW APPEARING ON THE NOME RADAR. MODERATE
ACCUMULATIONS OF SNOW ARE EXPECTED OVER THE NEXT FEW DAYS AS
MOISTURE CONTINUES TO STREAM UP FROM THE SOUTH. TEMPERATURES WILL
WARM TO NEAR FREEZING IN THE SOUTHERN PORTIONS OF ZONES 214 AND
215 BRINGING THE CHANCE OF SOME FREEZING RAIN AND POSSIBLY A
CHANGEOVER TO PLAIN RAIN BY THURSDAY IN THESE LOCATIONS. AS LOW PRESSURE
DEEPENS IN BRISTOL BAY NORTHEAST WINDS WILL STRENGTHEN BRINGING
BLOWING SNOW TO AREAS STRADDLING THE BERING SEA.

INTERIOR...CLOUDS HAVE OVERSPREAD ALL OF OUR INTERIOR ZONES AND
SOME VERY LIGHT SNOW HAS BROKEN OUT AS FAR NORTH AS FAIRBANKS AND
TANANA. ANY ACCUMULATION IN THESE LOCATIONS TODAY SHOULD BE VERY
LIGHT. MORE SIGNIFICANT SNOWFALL IS MORE LIKELY ON THE SOUTHERN
SLOPES OF THE ALASKA RANGE ALTHOUGH IN THESE LOCATIONS WARMER AIR
MAY BRING WITH IT THE CHANCE OF FREEZING RAIN. AS LOW PRESSURE
DEEPENS IN BRISTOL BAY THE LOW AND MID LEVEL FLOW SHOULD BECOME
MORE SOUTHERLY AND A DECENT CHINOOK PATTERN SHOULD SET UP. IN FACT
FAIRBANKS WILL LIKELY REACH ABOVE THE 20F MARK FOR THE FIRST TIME
SINCE OCTOBER ON WEDNESDAY OR THURSDAY. ACCUMULATING SNOWFALL WILL
BE RESTRICTED TO ZONES 218-220 AWAY FROM THE DRYING IMPACT OF THE
CHINOOK.

EXTENDED...ALTHOUGH DIFFERENT IN THEIR PLACEMENT OF SPECIFIC
DISTURBANCES THE GLOBAL MODELS ARE ALL IN AGREEMENT THAT NORTHERN
ALASKA WILL REMAIN IN A BATTLE GROUND BETWEEN A TROUGH OVER THE
BERING SEA AND A RIDGE OVER THE ALCAN BORDER. THIS MEANS THAT
UNSETTLED WEATHER IS LIKELY TO PERSIST THROUGH THE WEEKEND AND
INTO EARLY NEXT WEEK.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR AKZ225-AKZ226.

SNOW ADVISORY FOR AKZ215-AKZ216-AKZ217.

WINTER WEATHER ADVISORY FOR AKZ219-AKZ220-AKZ221.

GALE WARNING FOR PKZ210.

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

JMA DEC 05