Blizzard and High Wind in Alaska, November 3 to 4, 2010

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
140 PM AKDT WED NOV 3 2010

.UPPER LEVELS...A HIGH AMPLITUDE UPPER LEVEL PATTERN COVERS THE
FORECAST REGION TODAY WITH A DEEP TROUGH THAT STRETCHES FROM THE
BERING...ACROSS THE GULF...AND FAR INTO THE NORTH PACIFIC. AN
EMBEDDED UPPER LEVEL LOW IS CURRENTLY SOUTHEAST OF KODIAK ISLAND.
TO THE EAST A POTENT RIDGE EXTENDS FROM THE ROCKIES AND INTO
CENTRAL ALASKA. A STRONG UPPER LEVEL JET BETWEEN THESE FEATURES IS
TRANSPORTING A SIGNIFICANT AMOUNT OF MOISTURE NORTHWARDS TOWARDS
THE EAST AND CENTRAL GULF COAST AS SEEN IN THE WATER VAPOR IMAGERY
THIS MORNING. THE STRONG JET SUPPORT AND COPIOUS MOISTURE WILL HELP
TO SUPPORT THE DEEPENING OF A SURFACE LOW IN THE GULF OVER THE
NEXT 24 HOURS. MEANWHILE OUT WEST...A BROAD RIDGE THAT COVERS THE
BERING AND NORTH PACIFIC IS SUPPORTING RELATIVELY QUIESCENT WEATHER.

.SURFACE...A LOW PRESSURE SYSTEM OVER THE CENTRAL GULF OF ALASKA IS
QUICKLY MOVING TOWARDS THE GULF COAST AND WILL BE IMPACTING MUCH OF
THE SOUTHCENTRAL FORECAST AREA THROUGH THURSDAY BEFORE IT MOVES
INLAND AND DISSIPATES. IR SATELLITE IMAGERY IS INDICATING AN
IMPRESSIVE PRECIPITATION SHIELD TO THE NORTHEAST OF THE STORM WHILE
RADAR IS INDICATING STEADY PRECIPITATION ACROSS THE NORTH GULF COAST
WHICH WILL CONTINUE TO MOVE INLAND. THE LOW PRESSURE SYSTEM IS
EXPECTED TO REACH THE INTENSITY OF 959 MB AS IT OCCLUDES. THE
PROXIMITY OF THE OCCLUDED FRONT TO THE COAST AND INTENSITY OF THE
LOW WILL HELP TO SUPPORT STRONG WINDS WITH GUSTS UP TO 75 MPH ALONG
THE COAST EARLY THIS EVENING THROUGH THURSDAY MORNING. OUT
WEST...WEAK RIDGING IS OVER THE CENTRAL BERING WHILE TWO WEAK
LOWS ARE DEVELOPING ALONG THE KAMCHATKA PENINSULA.

.MODEL DISCUSSION...MODELS ARE IN GENERALLY GOOD AGREEMENT TODAY
WITH SOME DISCREPANCIES IN THE TIMING OF WEAKER SHORTWAVES IN THE
SHORT TERM. THE GFS APPEARS TO BE CAPTURING THE MAIN FEATURES MOST
CORRECTLY AND IS SHOWING GOOD RUN TO RUN CONSISTENCY. ALTHOUGH MODELS
DIVERGE SIGNIFICANTLY IN THE MID AND LONG TERMS...THEY ARE CURRENTLY
SHOWING THE SAME BASIC FEATURES WITH THE NEXT GULF LOW MOVING INLAND
INTO THE GULF COAST BY THE MIDDLE OF THE WEEKEND AND A WEAK LOW IN
THE WEST BERING.

.SOUTHCENTRAL...THE APPROACHING LOW PRESSURE SYSTEM AND ASSOCIATED
FRONT WILL IMPACT MUCH OF SOUTHCENTRAL THROUGH TOMORROW AS IT MOVES
FROM THE CENTRAL GULF AND INTO THE SUSITNA VALLEY. AS THE LOW AND
FRONT APPROACH THE GULF COAST...STRONG WINDS ARE EXPECTED TO OCCUR
ALONG THE COAST WITH WIND GUSTS UP TO 75 MPH. A SIGNIFICANT AMOUNT OF
MOISTURE IS ASSOCIATED WITH THIS SYSTEM AND WIDESPREAD PRECIPITATION
IS EXPECTED ACROSS THE SOUTHCENTRAL REGION. ALTHOUGH THE
PRECIPITATION WILL BEGIN AS SNOW THIS EVENING...THE OCCLUDED FRONT
WILL USHER IN ENOUGH WARM AIR TO CHANGE THE PRECIPITATION TO MOSTLY
RAIN AT LOWER ELEVATIONS OVERNIGHT. HOWEVER...SLIPPERY CONDITIONS
ARE POSSIBLE ON LOCAL ROADS AS RAIN AND SNOW FALLS ON RESIDUAL SNOW
FROM THE PREVIOUS SYSTEM. COLD AIR TRAPPED WITHIN THE COPPER RIVER
VALLEY WILL HELP TO PRODUCE STEADY SNOW BEGINNING THIS AFTERNOON. THE
HEAVIEST SNOW WILL BE ALONG THE SOUTHERN TO WESTERN BASIN...WITH SOME
ENHANCEMENT FROM UPSLOPE FLOW. A WINTER WEATHER ADVISORY FOR SNOW
HAS BEEN ISSUED FOR THESE AREAS. MORE SIGNIFICANT SNOW IS EXPECTED
IN THE HIGHER ELEVATIONS OF THOMPSON PASS WHERE HEAVY SNOW AND GUSTY
WINDS ARE EXPECTED TO CREATE BLIZZARD CONDITIONS STARTING LATE THIS
AFTERNOON.

.SOUTHWEST MAINLAND...THE LOW PRESSURE SYSTEM MOVING INTO THE GULF
WILL STAY TO THE EAST. AS A RESULT...ONLY LIGHT SNOW SHOWERS ARE
EXPECTED ALONG MOUNTAINOUS REGIONS. LOW STRATUS IS EXPECTED
ESPECIALLY ALONG THE COAST WHERE ONSHORE FLOW IS OCCURRING.

.ALEUTIANS AND BERING...A WEAK SURFACE LOW WEST OF THE KAMCHATKA
PENINSULA HAS A FRONT THAT EXTENDS INTO THE CENTRAL AND EAST
ALEUTIAN ISLANDS. LIGHT SNOW HAS BEEN OCCURRING AT DUTCH HARBOR
THIS MORNING WHILE TEMPERATURES ARE WARM ENOUGH FOR STEADY RAIN
ACROSS THE CENTRAL ALEUTIANS. A SEPARATE LOW PRESSURE SYSTEM WILL
APPROACH SHEMYA THIS AFTERNOON AND BRING THE CHANCE FOR SHOWERS
AS IT MOVES ACROSS THE ALEUTIANS THE NEXT SEVERAL DAYS. SOME GALE
FORCE WINDS ARE POSSIBLE AS IT BRIEFLY INTENSIFIES TO 975 MB
THURSDAY MORNING NORTH OF THE CENTRAL ALEUTIANS.

.LONG TERM...AN ACTIVE PATTERN WILL CONTINUE OVER THE NEXT
WEEK...ALTHOUGH MODELS ARE INDICATING THAT THE UPPER LEVEL RIDGES
AND TROUGHS WILL BE LOWER AMPLITUDE. MODELS ARE CURRENTLY NOT
INDICATING ANY MORE STRONG COLD AIR SURGES SOUTHWARD...SO EXPECT
RELATIVELY MILD PATTERN TO CONTINUE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...131. HIGH WIND WARNING...135.
MARINE...HURRICANE FORCE WIND WARNING...120.
         STORM WARNING...125 130 132.
         GALE WARNING...140 141 150 176.

ELN NOV 10

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
150 PM AKDT WED NOV 3 2010

AKZ101-040600-

...RAIN AND SNOW WILL CONTRIBUTE TO SLIPPERY ROADS ACROSS THE
REGION TONIGHT...

SNOW IS EXPECTED TO BEGIN LATE THIS AFTERNOON OVER THE ANCHORAGE
AREA AND CHANGE TO RAIN DURING THE EVENING. WHILE NO SIGNIFICANT
ACCUMULATION IS EXPECTED...RAIN AND SNOW WILL FALL ON SIDE ROADS
WHICH IN MANY CASES ARE COVERED IN SNOW FROM TUESDAY'S STORM. THE
ADDITIONAL RAIN AND SNOW WILL CONTRIBUTE TO HAZARDOUS DRIVING
CONDITIONS ALONG MANY OF THE LOCAL ROADS.

DRIVERS SHOULD USE CAUTION AND BE PREPARED TO ENCOUNTER SLICK ROADS.

ELN