Small Craft Advisory 70, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
547 AM AKST FRI JAN 23 2015

.ANALYSIS AND UPPER LEVELS...
THE MAJOR PLAYERS IN THIS EVENT REMAIN THE SAME WITH A BROAD
TROUGH SOUTH OF THE ALEUTIANS PUSHING AN ACTIVE SOUTHERLY FLOW
TOWARD AND OVER THE SOUTHCENTRAL MAINLAND. THE MOST NOTABLE
FEATURE ON WATER VAPOR IMAGERY AND ONE THAT DESCRIBES THE WHOLE
EVENT WELL IS A CLEAR DEMARCATION BETWEEN THE COLD/DRY ARCTIC AIRMASS
OVER THE INTERIOR...NORTH SLOPE...SOUTHWEST ALASKA AND THE
WARM/MOIST MARINE AIRMASS ON THE EAST/SOUTH SIDE OF THE ALASKA
RANGE. THE CLASH BETWEEN THESE TWO AIRMASSES ON THE LARGE SCALE IS
WHAT IS DRIVING THE ACTIVE WEATHER AROUND THE AREA...HOWEVER MANY
FINER DETAILS ON THE SMALLER SCALE WILL AFFECT SNOWFALL MAGNITUDE
AND DISTRIBUTION. THE FRONTAL BOUNDARY/DEFORMATION ZONE THAT MOVED
OVERHEAD ANCHORAGE YESTERDAY AFTERNOON AND EVENING IS NOW PARKED
TO THE WEST OVER COOK INLET...EXTENDING NORTHWARD INTO THE SUSITNA
VALLEY. A FRONTAL LIKE FEATURE IS MOVING FROM SOUTH TO NORTH OVER
THE KENAI PENINSULA WITH PAIH/PAHG RADARS SUGGESTING SPATIAL
CONTINUITY...LIKELY ABOVE MOUNTAIN TOP. THIS FEATURE LOOKS TO BE
WELL CORRELATED TO THE 300K ISENTROPIC SURFACE AND SHOULD CONTINUE
TO SPREAD SNOW OVER MOST AREAS INDEPENDENT OF THE AFOREMENTIONED
BAROCLINIC ZONE. THE PROGRESSION OF THE FORECAST THIS MORNING
LOOKS TO BE OVERRUNNING PRECIPITATION FOLLOWED BY WESTERLY COLD
ADVECTION AND FINALLY UPPER TROUGH PASSAGE.

&&

.MODEL DISCUSSION...
THE DIFFERENCES THAT PLAGUED INDIVIDUAL GUIDANCE SOLUTIONS
YESTERDAY CONTINUE TO DO THE SAME TODAY. MOST OF THE DISCREPANCY
SEEMS TO BE CENTERED ON HOW MUCH PRECIPITATION FALLS FROM KENAI
THROUGH THE MATANUSKA VALLEY TO THE EAST OF THE FRONTAL
BOUNDARY/DEFORMATION ZONE. THE APPEARANCE ON RADAR SUGGESTS THE
ZONE IS TOO FAR TO THE WEST AND NEEDS TO MIGRATE EAST BEFORE
INFLUENCING THE COOK INLET REGION. FOR THE MOST PART FEATURES ON
THE SYNOPTIC SCALE ARE PRETTY WELL AGREED UPON. THE NAM SEEMS TO
BE A FEW HOURS SLOWER WITH THE UPPER TROUGH PASSAGE ON SATURDAY
AFTERNOON...WHICH WOULD LEAVE FAVORABLE DYNAMICS OVER ANCHORAGE
AND THE MATANUSKA VALLEY LONGER. THERE IS MUCH BETTER AGREEMENT ON
PRECIPITATION AMOUNTS WITH COLD ADVECTION/TROUGH PASSAGE WITH THE
00Z/06Z MODELS SAVE THE GFS WHICH CONTINUES TO SEEMINGLY
UNDERPERFORM WITH PRECIPITATION AMOUNTS THOUGH THE SAME DYNAMICS
REMAIN IN PLACE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
ANOTHER SHOT OF OVERRUNNING SNOW LOOKS TO HIT THE KENAI PENINSULA
THROUGH THE MATANUSKA VALLEY THIS MORNING. SOME UNCERTAINTY STILL
EXISTS FOR THE AFTERNOON HOURS BUT PERIODS OF SNOW THROUGHOUT THE
DAY LOOK LIKELY IN MOST AREAS WITH ACCUMULATIONS. THE FRONT STILL
SITS OFF TO THE WEST OVER THE INLET AND WILL BEGIN TO TRACK EAST
DURING THE LATE AFTERNOON AND EVENING HOURS. AT THIS POINT COLD
ADVECTION WILL BEGIN TO WORK IN THE LOW LEVELS AND START THE
HEAVIEST PERIOD OF SNOW THROUGH THE OVERNIGHT HOURS INTO SATURDAY
MORNING. SNOW WILL TAPER OFF FROM WEST TO EAST SATURDAY
AFTERNOON/EVENING. ONCE THE SYSTEM PROGRESSES EASTWARD SNOW WILL
PICK UP IN THE COPPER RIVER BASIN ON SATURDAY FOR ANOTHER ROUND OF
ACCUMULATING SNOW.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TODAY THROUGH SATURDAY)...
THE LOW WIND CHILLS OVER THE SOUTHWEST MAINLAND WILL SLOWLY
IMPROVE LATER THIS MORNING AS THE NORTHERLY FLOW AND COLD AIR
ADVECTION DIMINISH. THIS WILL LEAVE CLEAR SKIES AND SOME OF THE
COLDEST TEMPERATURES OF THE SEASON FOR THE NEXT TWO
NIGHTS...ESPECIALLY FOR THE USUAL COLD SPOTS IN THE KUSKOKWIM
VALLEY AND INTERIOR KUSKOKWIM DELTA WHERE OVERNIGHT LOW
TEMPERATURES WILL APPROACH 30 BELOW ZERO. SNOW WILL CONTINUE OVER
EXTREME EASTERN BRISTOL BAY THROUGH LATE THIS MORNING AS THE
DEFORMATION BAND SLOWLY CLEARS FROM THE WEST. THIS BAND WILL
LIKELY REMAIN JUST OFF TO THE EAST...KEEPING SNOW SHOWERS OVER THE
ALEUTIAN AND ALASKA RANGES INTO SATURDAY...BUT THESE SHOULD REMAIN
EAST OF THE POPULATED AREAS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TODAY THROUGH SATURDAY)...
MOST OF THE REGION WILL REMAIN UNDER THE CURRENT NORTHERLY FLOW
AND COLD AIR ADVECTION REGIME INTO SATURDAY. THE ONE EXCEPTION TO
THIS WOULD BE THE WESTERN ALEUTIANS WHICH WILL SEE MORE WIDESPREAD
SNOW SHOWERS TODAY WITH A WEAK SHORTWAVE PASSING JUST OFF TO THE
NORTH. AFTER A BRIEF PERIOD OF CLEARING TOMORROW...THE NEXT
ALEUTIAN LOW WILL THEN APPROACH THE WESTERN ALEUTIANS ON LATE
SATURDAY BEFORE SPREADING INTO THE CENTRAL ALEUTIANS FOR SUNDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THIS TIME FRAME WILL BE KNOWN FOR THE MUCH COLDER AIR ACROSS MUCH
OF THE FORECAST AREA. GENERALLY DRY AND COLD CONDITIONS CAN BE
EXPECTED AFTER THE UPPER TROUGH AXIS PASSES OFF TO THE EAST.
BELOW ZERO TEMPERATURES ARE FORECAST FOR MUCH OF THE SOUTHERN
MAINLAND...EXCEPT MAINLY COASTAL AREAS...WITH FRESH SNOWCOVER AND
A COLD AIRMASS SPREADING EASTWARD OVER THE AREA. ACROSS THE BERING
SEA AND ALEUTIANS...A LARGE LOW WILL PASS BY TO THE SOUTH OF THE
ALEUTIANS...BRINGING PERIODS OF RAIN AND SNOW LATE THIS WEEKEND
AND EARLY NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY 101 111 121 125 131 141 145.
MARINE...GALE WARNING 130 131 150 155 160 165 170 172 173 174 180.
         HEAVY FREEZING SPRAY 130 138 160 165 170 180 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...ML
SOUTHCENTRAL ALASKA...ML
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...MBS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
930 AM AKST FRI JAN 23 2015

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

0500 AM     SNOW             BIG LAKE                61.52N 149.95W
01/23/2015  M4.2 INCH                           AK   NWS EMPLOYEE

            4.25 INCHES NEAR INTERSECTION OF BIG LAKE ROAD AND BIG
            LAKE LODGE ROAD AS OF 5 AM 1/23.

&&

CCASSELL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1046 AM AKST FRI JAN 23 2015

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

0949 AM     SNOW             EAGLE RIVER             61.32N 149.57W
01/23/2015  E0.5 INCH                           AK   PUBLIC

            MULTIPLE REPORTS WITH ESTIMATES BETWEEN 0.5 INCHES AND
            2.0 INCHES THROUGHOUT EAGLE RIVER.

0949 AM     SNOW             PALMER                  61.60N 149.11W
01/23/2015  E0.0 INCH                           AK   PUBLIC

            DUSTING OF SNOW NEAR TRUNK ROAD AS OF 7 AM 1/23.

0949 AM     SNOW             WILLOW                  61.74N 150.06W
01/23/2015  M4.8 INCH                           AK   PUBLIC

            4.75 INCHES NEAR MILE 69 PARKS HIGHWAY AS OF 7 AM.

0949 AM     SNOW             KASILOF                 60.33N 151.23W
01/23/2015  E4.0 INCH                           AK   PUBLIC

            STILL SNOWING AS OF 7 AM 1/23.

0949 AM     SNOW             1 S ANCHORAGE           61.20N 149.87W
01/23/2015  E2.0 INCH                           AK   PUBLIC

            MULTIPLE REPORTS OF APPROXIMATELY 2 INCHES MIDTOWN
            ANCHORAGE.

0949 AM     SNOW             NIKISKI                 60.73N 151.38W
01/23/2015  E4.5 INCH                           AK   PUBLIC

            4.5 INCHES ESTIMATED NEAR NIKISKI AND STILL SNOWING AS OF
            7 AM 1/23.

0949 AM     SNOW             HOUSTON                 61.62N 149.78W
01/23/2015  M4.5 INCH                           AK   PUBLIC

            4.5 INCHES MEASURED NEAR MILE 54.5 PARKS HIGHWAY AS OF 7
            AM 1/23.

0949 AM     SNOW             TALKEETNA               62.34N 150.09W
01/23/2015  E5.0 INCH                           AK   PUBLIC

            MILE 11 TALKEETNA SPUR ROAD

0949 AM     SNOW             TRAPPER CREEK           62.24N 150.42W
01/23/2015  E0.0 INCH                           AK   PUBLIC

            4 INCHES ESTIMATED NEAR PETERSVILLE AS OF 8 AM 1/23.

0949 AM     SNOW             WASILLA                 61.58N 149.46W
01/23/2015  M0.3 INCH                           AK   PUBLIC

            0.3 INCHES MEASURED NEAR MIDDLE OF WASILLA.

&&

RDUELL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1105 AM AKST FRI JAN 23 2015

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

1013 AM     SNOW             THOMPSON PASS           61.14N 145.75W
01/23/2015  M7.0 INCH                           AK   DEPT OF HIGHWAYS

            DEPARTMENT OF TRANSPORTATION REPORTED 7 INCHES OF SNOW IN
            THE PAST 24 HOURS.

1013 AM     SNOW             11 E VALDEZ             61.06N 145.99W
01/23/2015  M4.0 INCH                           AK   DEPT OF HIGHWAYS

            4 INCHES OF SNOW MEASURED. SOME GRAUPEL WAS MIXED IN
            OVERNIGHT.

&&

RDUELL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1239 PM AKST FRI JAN 23 2015

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

0730 AM     FREEZING RAIN    SEWARD                  60.11N 149.39W
01/23/2015  U0.00 INCH                          AK   LAW ENFORCEMENT

            LIGHT FREEZING RAIN IN THE MORNING HOURS, SWITCHING TO
            ALL LIGHT RAIN BY 8AM.

0748 AM     SNOW             3 S STERLING            60.47N 150.80W
01/23/2015  M2.7 INCH                           AK   PUBLIC

            TOTAL SNOW ACCUMULATION SO FAR, 2 3/4 INCHES. NOT SNOWING
            AT PRESENT TIME.

&&

RDUELL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
155 PM AKST FRI JAN 23 2015

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

0153 PM     SNOW             MOOSE PASS              60.47N 149.39W
01/23/2015  E2.0 INCH                           AK   PUBLIC

            ESTIMATED TWO INCHES OF SNOW ACCUMULATION. CURRENTLY NOT
            SNOWING.

0153 PM     SNOW             7 SSW BIG LAKE          61.43N 150.03W
01/23/2015  M4.0 INCH                           AK   PUBLIC

            MEASURED 4 INCHES OF SNOW THIS MORNING AT 10AM. STOPPED
            SNOWING DURING LATE MORNING HOURS. SNOW STARTED AGAIN
            BEGINNING AT 130PM.

&&

RDUELL