Blizzard Watch 26, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST MON DEC 16 2013

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVEL LOW CENTERED OVER THE
NORTHEASTERN GULF OF AK CONTINUES TO WEAKEN THIS MORNING. THE 140 KT
JET THAT WAS SUPPORTING IT WILL CONTINUE TO MOVE OFF INTO CANADA
THROUGH THE DAY. TO THE WEST...THE UPPER LEVELS REMAIN QUITE QUIET
WITH MAINLY LIGHT ZONAL FLOW. IN THE MID AND LOWER LEVELS BENEATH
THIS ZONAL FLOW IS SOME MODERATE RIDGING OVER THE BERING. A COMPLEX
AREA OF LOWER PRESSURE IS STARTING TO GET ORGANIZED SOUTH OF THE
WESTERN ALEUTIANS.

.MODEL DISCUSSION...THE MODELS ARE IN SOLID AGREEMENT THROUGH EARLY
WEDNESDAY MORNING. THEY REMAIN IN GOOD AGREEMENT OVER THE MAINLAND
AND GULF OF AK THROUGH THURSDAY AFTERNOON. THE ONE SIGNIFICANT
DIFFERENCE IS THAT THE GFS MOS GUIDANCE DOES NOT DEVELOP ANY FOG FOR
ANCHORAGE UNTIL LATE TUESDAY NIGHT WHEREAS THE NAM MOS BRINGS IT IN
STARTING TODAY. SOME MODERATE DIFFERENCES DEVELOP OVER THE CENTRAL
ALEUTIANS REGARDING THE STRENGTH OF THE LOW PRESSURE CENTER ON
WEDNESDAY. THUS...THE NAM WAS USED FOR THE FIRST 48 HRS OF THE
FORECAST IN THE EAST...THEN A BLEND OF THE GFS AND EC WAS PREFERRED.
OUT WEST...A GFS/EC BLEND WAS PREFERRED THROUGHOUT THE SHORT TERM.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...PATCHY FOG HAS ALREADY STARTED TO MOVE INTO THE
ANCHORAGE BOWL THIS MORNING. IT APPEARS TO BE HUGGING ALONG THE KNIK
ARM STRETCHING FROM JBER TOWARDS EAGLE RIVER. WITH A VERY WEAK
INVERSION PRESENT ON THE MORNING SOUNDING...THINKING IS THAT IT WILL
BE TEMPORARY THROUGH THIS MORNING. DRY NORTHWESTERLY FLOW SHOULD HELP
IT TO ABATE. BUT AS THE PREVIOUSLY MENTIONED RIDGE CONTINUES TO SHIFT
EAST FROM THE BERING TOWARDS THE MAINLAND TODAY...TEMPERATURES IN THE
LOW TO MID LEVELS WILL CLIMB EVER-SO-SLOWLY. THIS SHOULD MAKE FOR
SLIGHTLY BETTER TRAPPING UNDER A STRONG INVERSION TOMORROW MORNING.
THIS WILL ALLOW THE FOG TO BECOME MUCH MORE WIDESPREAD. WITH THE SUN
ANGLE AS LOW AS IT IS WITH THE SOLSTICE ONLY A FEW DAYS AWAY...THERE
IS A GOOD CHANCE THE FOG WONT BURN OFF DURING THE AFTERNOON. THE
OTHER STORY FOR THE REGION WILL BE GUSTY OUTFLOW WINDS THROUGH THE
TYPICAL FAVORED AREAS..ESPECIALLY NEAR THE COAST. THESE WINDS COUPLED
WITH PLENTY OF NEW SNOW IN THOMPSON PASS COULD MAKE FOR POOR
VISIBILITY IF THE SNOW GETS AIRBORNE. A BLIZZARD WATCH HAS BEEN
ISSUED TO ADDRESS THIS.
THE NEXT CHANCE FOR PRECIPITATION WILL COME IN THE FORM OF A WARM
FRONT FROM THE SOUTHWEST LATE WEDNESDAY INTO THURSDAY. AT THIS TIME
IT APPEARS THAT THIS WILL JUST BRING A GLANCING BLOW OF OVERRUNNING
SNOW TO MOST OF SOUTH CENTRAL. COASTAL LOCATIONS...ESPECIALLY THOSE
IN OR EAST OF PRINCE WILLIAM SOUND...WILL SEE THE MOST ACCUMULATION.

SOUTHWEST ALASKA...WEATHER WILL REMAIN RELATIVELY QUIET UNTIL THE
NEXT LOW FROM THE NORTH PACIFIC REACHES THE SOUTHWEST MAINLAND ON
WEDNESDAY. WHILE WARM AIR WILL COME WITH THIS SYSTEM...THE WARMEST
TEMPERATURES SHOULD REMAIN ALONG AND SOUTH OF THE ALASKA PENINSULA
AND LEAVE PRECIPITATION TYPE AS SNOW OVER THE SOUTHWEST MAINLAND AS
TEMPERATURES THERE REMAIN BELOW FREEZING.

ALEUTIANS/BERING SEA...THE NORTH PACIFIC LOW WILL AFFECT THE
ALEUTIANS BEGINNING LATE TONIGHT AND WEDNESDAY...WITH INCREASING
WINDS AS THE LOW MOVES NORTHWARD AND THE ASSOCIATED FRONT PUSHES
EASTWARD. IT STILL LOOKS LIKE STRONG WINDS ARE REASONABLE ALONG
ESPECIALLY THE CENTRAL AND EASTERN ALEUTIANS.

AS THE PRECIPITATION REACHES THE PRIBILOF ISLANDS...PRECIPITATION
TYPE IS IN QUESTION...WITH TEMPERATURES WITHIN A FEW DEGREES OF
FREEZING. WINDS WILL PICK UP ALONG WITH THE PRECIPITATION...BUT EVEN
IF PRECIPITATION TYPE IS SNOW WE DO NOT EXPECT BLIZZARD CONDITIONS AT
THIS TIME DUE TO THE RELATIVELY WARM TEMPERATURES.

.LONG TERM FORECAST (FRIDAY-SUNDAY)...MOST OF THE MODELS CONTINUE TO
ADVERTISE A FAIRLY ROBUST NORTH PACIFIC RIDGE PLAYING A SIGNIFICANT
ROLE IN OUR WEATHER FOR THE WEEKEND. THE EC BUILDS THE RIDGE OVER THE
MAINLAND A BIT MORE WHICH MAKES FOR A MORE AMPLIFIED PATTERN. THIS
OPENS MUCH OF SOUTHCENTRAL TO WARMER AIR FROM THE SOUTHWEST. HATE TO
SAY IT...BUT THIS COULD SPELL ANOTHER ROUND OF MIXED PRECIPITATION TO
START THE WEEKEND. THE GFS KEEPS THE RIDGE A BIT FURTHER SOUTH IN THE
GULF OF AK AND KEEPS EVERYONE EXCEPT THE COASTAL AREAS IN A
COLDER...SNOWY PATTERN. MODELS THEN BUILD ANOTHER FAIRLY DEEP AND
VERY BROAD AREA OF LOW PRESSURE OVER THE WESTERN ALEUTIANS LATE
SUNDAY INTO MONDAY

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH: 131.
MARINE...STORMS: 176.
         GALES: 172 173 174 175 177 178 411 413 127 129 131.
         HEAVY FREEZING SPRAY: 150 160 121 126 127 128 129 130 131
                               132 138 139.
FIRE WEATHER...NONE.

MSO/MBS DEC 13