Heavy Freezing Spray Warning 38, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
130 PM AKST FRI JAN 13 2012

CORRECTS SPELLING AND ZONE CLARIFICATION

VAST PATTERN SHIFT CONTINUING ON COURSE WITH VERY LITTLE NOTICEABLE
CHANGE FROM THURSDAYS FORECAST. AREA OF CLOUDS AND LITE SNOW SUSITNA
VALLEY AND KENAI PENINSULA SLOWLY EDGING EASTWARD AS ADVANCING BERING
SEA FRONT KEEPS THE PATTERN SOMEWHAT PROGRESSIVE. AREAS OF LITE SNOW
SLIDING SOUTHEAST OVER AND ALONG THE SOUTHWEST COAST HAS JUST ABOUT
ENDED FRIDAY AFTERNOON. UPPER RIDGE AXIS IN THE EASTERN BERING TO
SHIFT INLAND TO LIE ALONG 158W OR SO SATURDAY AFTERNOON. RIDGE IS
THEN FLATTENED BY A MUCH WEAKENED FRONT THAT REACHES THE WEST COAST
SATURDAY NIGHT AND MOVES INLAND SUNDAY MORNING. AREAS OF LIGHT SNOW
OR FLURRIES WILL ACCOMPANY THIS FEATURE, HOWEVER, LITTLE IF ANYTHING
WILL REACH OR PASS THE WESTERN ALASKA RANGE. THIS WEAK UPPER IMPULSE
DROPS SOUTHEAST ACROSS KODIAK ISLAND SUNDAY AS STRONGER RIDGE BUILDS
IN OVER THE EASTERN BERING SEA. THIS RIDGE WILL EVOLVE INTO A VERY
FORMIDABLE BLOCK ACROSS THE NORTHERN BERING SEA AS EARLY AS SUNDAY
NIGHT AND REMAIN STATIONARY THROUGH MONDAY. NORTHERLY FLOW ALOFT WILL
BLOW ACROSS ALL OF MAINLAND ALASKA AND THE PANHANDLE SUNDAY, MONDAY
AND TUESDAY. WAVELENGTH OF NORTHERN BERING BLOCK BECOMES LARGE ENOUGH
TO ALLOW RETROGRESSIVE FORCES TO PUSH THE RIDGE CENTER WESTWARD OVER
EASTERN RUSSIAN BETWEEN 175E AND 180 ON WEDNESDAY. THE ONLY EFFECT OF
THIS WILL BE TO DEFLECT NORTHWEST PACIFIC STORMS WEST OF EVEN THE
SHEMYA ATTU AREA WITH AN INVERTED EASTERLY FLOW ALONG THE ALEUTIANS.

VERY COLD AIR THAT'S BEEN OVER WESTERN ALASKA MOVING EASTWARD WITH
-54 AT MERRILL PASS STONEY RIVER THIS MORNING, AND -30 PORT ALSWORTH.
CLEARING AREAS OF SUSITNA VALLEY WILL ALLOW READINGS TO DROP TO 30 TO
35 BELOW IN THE WIND AND CLOUD FREE AREAS OF THE SUSITNA VALLEY AND
WESTERN COOK INLET, SUCH AS WILLOW AND MAYBE SKWENTNA. KENAI
PENINSULA MATANUSKA VALLEY AREAS AND EAST WILL BE WARMER DUE TO
LINGERING CLOUD COVER AND SOME WIND. SAT EVENING AND NIGHT WILL BE
MUCH COLDER ACROSS THESE AREAS WHILE THE WESTERN MAINLAND, ESPECIALLY
THE COAST, WARMS WITH INCOMING FRONTAL REMNANTS. COPPER RIVER
BASIN (141) WILL LIKELY DROP INTO THE -30 TO -40 TEMPERATURE RANGE
AND THE KENAI PENINSULA IN THE -10 TO -30 BELOW RANGE. WINDY AREAS
MAY HAVE CHILLS FALL TO ADVISORY LEVELS.

CURRENT WIND FORECASTS LOOK ON THE BUTTON WITH POSSIBLE GUSTS 35 TO
40 MPH IN THE MATANUSKA VALLEY AND GUSTS TO OR OVER 60 MPH IN THE
CHANNELED AREAS OF PRINCE WILLIAM SOUND AND THE NORTH GULF COAST.
THIS MAY INITIALLY RESULT IN A BRIEF GROUND BLIZZARD AT PLACES LIKE
THOMPSON PASS. PREFRONTAL STORM FORCE WINDS HAVE ENDED WITH THE
BERING SYSTEM AND REMAINING GALES WILL FALL TO THE 15 TO 25 KT RANGE
BY SATURDAY EVENING.

NO RECORD LOW TEMPERATURES EXPECTED THE NEXT 5 DAYS SINCE THE POLAR
VORTEX NOW NORTH OF THE ARCTIC COAST IS MOVING OFF OVER THE NORTHWEST
TERRITORIES TO CENTRAL CANADA, TAKING THE COLDEST PORTION OF THE
AIRMASS WHICH HAS THE POTENTIAL FOR RECORD LOW TEMPERATURES WITH IT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING THOMPSON PASS TONIGHT (131).
MARINE...GALES AREAS 121 129 132 138 170 175 179 180 185
         HEAVY FREEZING SPRAY AREAS 120 121 126 127 128 129 130 132
                                    138 140 141 150
FIRE WEATHER...NONE.

PERCY JAN 12

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST FRI JAN 13 2012

AKZ101-142100-

...VERY COLD AND WINDY CONDITIONS FOR SOUTH CENTRAL ALASKA THIS
WEEKEND INTO NEXT WEEK...

THE WEATHER PATTERN ACROSS THE STATE IS CHANGING FROM THE FREQUENT
STORMS IN THE GULF TO A COLDER...DRIER AND WINDY PATTERN.
HIGH PRESSURE WILL BUILD OVER THE STATE TONIGHT THROUGH THE WEEKEND.
THE HIGH WILL CENTER ITSELF OVER THE CHUKCHI SEA EARLY NEXT WEEK.
THIS WILL RESULT IN VERY COLD ARCTIC AIR DIVING SOUTHWARD ACROSS
THE MAINLAND AND REMAINING IN PLACE THROUGH NEXT WEEK.

COLD AIR IS ALREADY IN PLACE AND WITH A CLEAR NIGHT SETTING UP
FOR SOUTH CENTRAL AND SOUTHWEST ALASKA OVERNIGHT TEMPERATURES OF
20 TO 40 BELOW ARE ANTICIPATED TONIGHT AND TOMORROW NIGHT. OVER THE
ANCHORAGE BOWL AND MATANUSKA VALLEY OVERNIGHT TEMPERATURES WILL BE
FROM 5 TO 20 BELOW. OVERNIGHT TEMPERATURES WILL REMAIN COLD THROUGH
THE WEEK. DAYTIME TEMPERATURES WILL BE HARD PRESSED TO REACH ABOVE
ZERO IN SOME VALLEYS OF INTERIOR LOCATIONS OF SOUTH CENTRAL ALASKA.

ALONG WITH THE VERY COLD TEMPERATURES...THE HIGH PRESSURE WILL
PRODUCE VERY STRONG WINDS FROM THE NORTH...ESPECIALLY THROUGH GAPS
IN THE TERRAIN. THE HIGHEST WINDS ARE ANTICIPATED FROM PRINCE
WILLIAM SOUND EASTWARD WHERE GUSTS COULD APPROACH 55 KT THROUGH
PASSES. WITH THE FRESHLY FALLEN SNOW...THE WINDS ARE CREATING
BLIZZARD CONDITIONS THROUGH THOMPSON PASS WHICH ARE NOT ANTICIPATED
TO END UNTIL SATURDAY MORNING. THE GUSTY WINDS WILL EXTEND INTO THE
MARINE AREAS AS WELL...AND COMBINE WITH THE VERY COLD TEMPERATURES
TO PRODUCE HEAVY FREEZING SPRAY THROUGH THE WEEKEND. IN
ADDITION...THE COMBINATION OF THE STRONG WINDS AND COLD TEMPERATURES
WILL CREATE VERY COLD WIND CHILLS RANGING FROM 20 TO 40 BELOW FOR
MANY INLAND LOCATIONS THROUGH THE WEEKEND.

JN