Gale Warning 745, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1250 PM AKST MON NOV 11 2013

.ANALYSIS AND UPPER LEVELS...AN UPPER LEVEL TROUGH HAS STALLED ALONG
155W (OVER INTERIOR SOUTHWEST ALASKA AND THE WESTERN GULF OF ALASKA)
IN BETWEEN TWO HIGH AMPLITUDE RIDGES CENTERED OVER THE NORTH CENTRAL
PACIFIC AND WESTERN U.S./CANADA. AT THE SURFACE...A WEAK SURFACE
LOW PRESSURE SYSTEM CENTERED JUST NORTH OF MIDDLETON ISLAND IS
MOVING SLOWLY EASTWARD WITH COLDER AND DRIER AIR MOVING IN BEHIND
IT. MODERATE TO HEAVY PRECIPITATION CONTINUES TO FALL FROM EASTERN
PRINCE WILLIAM SOUND TO THE COPPER RIVER BASIN...ALL SNOW WITH THE
EXCEPTION OF SOUTHEAST PRINCE WILLIAM SOUND. SINCE EVERYTHING IS
SLOW TO PROGRESS EASTWARD EXPECT PRECIP TO PERSIST THROUGH THE DAY
FOR MOST OF THESE AREAS.

THE NORTH PACIFIC RIDGE IS AMPLIFYING AND SLIDING EASTWARD AS AN
UPSTREAM TROUGH MOVES OUT OF ASIA. THE SUBTROPICAL JET RIDES UP
AND OVER THIS RIDGE. ON THE EAST SIDE OF THE RIDGE THE JET IS
COMBINING WITH LOW LEVEL COLD ADVECTION AND A TIGHT SURFACE PRESSURE
GRADIENT TO PRODUCE STRONG WINDS ALONG THE ALASKA PENINSULA AND
INTO THE WESTERN GULF. AS COLD AIR WORKS ITS WAY EASTWARD LOCALIZED
GAP WINDS HAVE ALSO DEVELOPED IN WESTERN PRINCE WILLIAM SOUND.

MEANWHILE A SOUTHERLY JET ON THE WEST SIDE OF THE RIDGE IS
TRANSPORTING VERY WARM MOIST AIR NORTHWARD FROM THE TROPICS AND
INTO THE WESTERN BERING. THE LEADING EDGE OF THIS AIR MASS...IN
THE FROM OF A WARM FRONT...IS MOVING OVER TOP OF THE RIDGE WITH
OVERRUNNING PRECIP SPREADING EASTWARD ACROSS THE BERING SEA.

.MODEL DISCUSSION...MODELS GENERALLY HAVE A GOOD HANDLE ON LARGER
SCALE FEATURES AND SHOW GOOD RUN-TO-RUN CONSISTENCY THROUGH THE
SHORT-TERM. THERE ARE A FEW KEY DIFFERENCES WITH HANDLING OF WARM
FRONT CROSSING THE SOUTHERN MAINLAND TUESDAY AND WEDNESDAY AND WITH
HANDLING OF A WEAK LOW WHICH FORMS NEAR THE SOUTHERN KENAI PENINSULA
TUESDAY NIGHT. THE 12Z NAM WAS MUCH MORE AGGRESSIVE IN BRINGING WARM
FRONTAL PRECIP INTO COOK INLET/THE WESTERN KENAI TUESDAY MORNING
BUT THE 18Z RUN HAS BACKED OFF AND LOOKS MUCH MORE SIMILAR TO OTHER
SOLUTIONS WITH VERY MINOR QPF SURVIVING THE TRIP ACROSS THE ALASKA
RANGE. THE GFS THEN BECOMES AN OUTLIER WITH TIMING OF A COLD FRONT
MOVING IN FROM THE NORTH AND WEST ON THURSDAY. ALL OF THIS LEADS TO
LOW CONFIDENCE IN THE QPF AND PRECIP-TYPE FORECASTS FOR SOUTHCENTRAL
WEDNESDAY AND THURSDAY. WHAT CAN BE SAID WITH SOME CONFIDENCE IS
THAT WITH THE TRANSITION FROM COLD TO WARM AND BACK TO COLD AGAIN
THIS IS A GOOD SET-UP TO PRODUCE A VARIETY OF PRECIP-TYPES.

.SHORT TERM FORECAST...THE UPPER RIDGE AND JET OVER THE BERING WILL
SLOWLY SLIDE EASTWARD TOWARD SOUTHCENTRAL TONIGHT HELPING TO WEAKEN
THE UPPER TROUGH AND PUSH IT OFF THE SOUTH AND EAST. PRECIP WILL
LINGER ACROSS PORTIONS OF THE COPPER BASIN AND EASTERN PRINCE
WILLIAM SOUND...BUT WILL BECOME MUCH LIGHTER AS WE HEAD THROUGH
THE EVENING HOURS AND THEN END BY TUESDAY MORNING. MEANWHILE...GAP
WINDS WILL STRENGTHEN ACROSS PRINCE WILLIAM SOUND AND THE NORTH
GULF COAST AS THE TROUGH MOVES THROUGH. A BLIZZARD WARNING IS IN
EFFECT FOR THOMPSON PASS WHERE WINDS AND FALLING SNOW WILL GIVE
WAY TO JUST BLOWING SNOW RESULTING IN A PROLONGED PERIOD OF REDUCED
VISIBILITIES. WINDS WILL WIND DOWN WEDNESDAY AFTERNOON AS ATTENTION
SHIFTS TO THE WARM FRONT MOVING IN FROM THE WEST.

GEFS (GLOBAL ENSEMBLE FORECAST SYSTEM) STANDARDIZED ANOMALIES FOR
PRECIPITABLE WATER...SPECIFIC HUMIDITY...AND TEMPERATURE ARE
SIGNIFICANT WITH VALUES GENERALLY BETWEEN 5 AND 8 AS THE WARM FRONT
MAKES ITS WAY ACROSS THE BERING SEA TO MAINLAND ALASKA. IN THE FEW
YEARS THIS DATA SET HAS BEEN AVAILABLE FOR USE IN OPERATIONS THESE
TYPE OF VALUES HAVE BEEN INDICATIVE OF POTENTIAL FOR SIGNIFICANT
FREEZING RAIN EVENTS. IN THIS CASE...THE SURFACE PATTERN DOESN'T
LOOK FAVORABLE FOR MAINTAINING COLD AIR AT THE SURFACE FOR MOST
AREAS. FOR COASTAL AREAS OF SOUTHWEST ALASKA WINDS WILL SHIFT TO
SOUTH AHEAD OF THE FRONT WHICH WILL HELP SURFACE TEMPERATURES WARM
UP RELATIVELY QUICKLY. THUS...THE TRANSITION FROM SNOW TO FREEZING
RAIN TO RAIN SHOULD BE QUICK AND ANY ICE ACCUMULATION VERY MINOR.
IT WILL BE MUCH MORE DIFFICULT TO ERODE ALL OF THE COLD AIR OVER
INTERIOR SOUTHWEST ALASKA...ESPECIALLY ACROSS THE SOUTHERN KUSKOKWIM
VALLEY...SO EXPECT A MORE PROLONGED PERIOD OF FREEZING RAIN WITH
ICE ACCUMULATION APPROACHING ONE QUARTER OF AN INCH. ARCTIC AIR
WILL RAPIDLY MOVE BACK INTO SOUTHWEST ALASKA WEDNESDAY NIGHT INTO
THURSDAY HELPING TO DRY THINGS OUT AND REFREEZE WHATEVER IS LEFT
ON THE GROUND.

AS MENTIONED ABOVE THE FORECAST FOR SOUTHCENTRAL IS A MUCH BIGGER
CHALLENGE. THE LATEST MODELS SEEM TO BE TRENDING TOWARD A DRIER
SOLUTION WITH ARRIVAL OF THE WARM FRONT ON WEDNESDAY. THUS...DON'T
EXPECT THIS TO BE A MAJOR FREEZING RAIN EVENT. NO MATTER WHETHER
PRECIP FALLS OR NOT THERE IS HIGHER CONFIDENCE THAT TEMPERATURES
WILL RISE ABOVE FREEZING FOR MUCH OF SOUTHCENTRAL WEDNESDAY
AFTERNOON INTO WEDNESDAY NIGHT...WHICH WILL MELT SOME OF THE SNOW
ON THE GROUND LIKELY LEADING TO ICY CONDITIONS. THE HIGHER
PROBABILITY OF PRECIP LOOKS WILL BE WITH THE COLD FRONT WHICH
APPROACHES WEDNESDAY NIGHT AND THEN MOVES THROUGH THURSDAY. EXPECT
RAIN OUT AHEAD OF THE FRONT CHANGING TO SNOW AND QUICKLY ENDING AS
THE FRONT PASSES THROUGH. ALL OF THESE TRANSITIONS WILL HAPPEN OVER
A RELATIVELY SHORT PERIOD OF TIME...MAKING IT DIFFICULT TO HONE IN
ON THE EXACT TIMING.

.LONG TERM FORECAST...THERE IS A PRETTY LARGE SPREAD IN MODEL
SOLUTIONS FOR THE DAY 4 THROUGH 7 PERIOD. HOWEVER...THERE ARE SOME
COMMONALITIES IN THE LARGER SCALE PATTERN. THE NORTH-PACIFIC RIDGE
WILL WEAKEN AS SYSTEMS CONTINUE TO TRACK INTO AND OVER TOP OF IT.
AFTER THE COLD FRONT MOVES THROUGH THE SOUTHERN MAINLAND THURSDAY
EXPECT ANOTHER WARM FRONT TO QUICKLY MOVE BACK IN FRIDAY LEADING
TO ANOTHER WARM-UP AND CHANCE OF RAIN AND/OR FREEZING RAIN. THERE
IS THEN PRETTY GOOD AGREEMENT THAT A MAJOR STORM SYSTEM WILL MOVE
INTO THE GULF EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 131.
         WINTER WEATHER ADVISORY...141 152.
         FREEZING RAIN ADVISORY 155.
MARINE...GALE WARNING...121 127 128 129 131 132 150 177 178 185.
FIRE WEATHER...NONE.

SEB NOV 13

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1136 AM AKST MON NOV 11 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0500 AM     SNOW             1 ENE CHICKALOON        61.80N 148.46W
11/11/2013  M14.0 INCH                          AK   TRAINED SPOTTER

            STORM TOTAL 14.0 INCHES.

0700 AM     SNOW             4 E ANCHORAGE           61.21N 149.74W
11/11/2013  M8.0 INCH                           AK   NWS EMPLOYEE

            6.0 INCHES THROUGH 10 PM. STORM TOTAL 8.0 INCHES.

0715 AM     SNOW             4 SW ANCHORAGE          61.18N 149.95W
11/11/2013  M6.0 INCH                           AK   NWS EMPLOYEE

            STORM TOTAL 6.0 INCHES

0815 AM     SNOW             1 E EAGLE RIVER         61.32N 149.54W
11/11/2013  M6.5 INCH                           AK   NWS EMPLOYEE

            6.5 INCHES STORM TOTAL.

0900 AM     SNOW             6 ESE SKWENTNA          61.97N 151.21W
11/11/2013  M2.0 INCH                           AK   CO-OP OBSERVER

            STORM TOTAL 2.0 INCHES

0900 AM     SNOW             1 S TALKEETNA           62.32N 150.09W
11/11/2013  M12.0 INCH                          AK   OTHER FEDERAL

            STORM TOTAL 12.0 INCHES

0900 AM     SNOW             26 NNE CHASE            62.82N 149.90W
11/11/2013  M18.0 INCH                          AK   CO-OP OBSERVER

            STORM TOTAL 18.0 INCHES

0900 AM     SNOW             4 NNW VALDEZ            61.13N 146.35W
11/11/2013  M24.0 INCH                          AK   NWS EMPLOYEE

            STORM TOTAL 24 INCHES SO FAR. STILL SNOWING.

1025 AM     SNOW             4 NNW BUTTE             61.59N 149.11W
11/11/2013  M3.5 INCH                           AK   OTHER FEDERAL

            STORM TOTAL 3.5 INCHES WET SNOW

&&

KUTZ