Small Craft Advisory 925, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
505 PM AKST THU NOV 21 2013

.ANALYSIS AND UPPER LEVELS...AN UPPER LOW HAS DEVELOPED OVER THE
EASTERN BERING WITH AN ASSOCIATED TROUGH INTO THE NORTH PACIFIC. A
RIDGE IS SITUATED ALONG THE EASTERN NORTH PACIFIC. THIS HAS LED TO A
PUSH OF WARMTH AND MOISTURE INTO THE GULF OF ALASKA TO SOUTHERN
ALASKA AND THE PANHANDLE. A MODERATE LOW PRESSURE SYSTEM IS JUST
SOUTH OF KODIAK ISLAND THIS AFTERNOON WITH GALE FORCE WINDS ACROSS
THE NORTHERN AND WESTERN GULF AND INNER WATERS. SNOW HAS BEGUN INLAND
THIS AFTERNOON OVER SOUTH CENTRAL ALASKA WITH LARGE AMOUNTS OF
SNOWFALL ALREADY OCCURRING IN THE PANHANDLE. BACKSIDE OF THE LOW IN
THE BERING BRINGING SOME COLD AIR AND MODERATE WINDS. WITH THE OPEN
WATER...CONVECTIVE SNOW SHOWERS ARE OCCURRING. ANOTHER LOW WEST OF
ATTU TO PUSH IN SOME PRECIP AND STRONGER WINDS TO THE WESTERN
ALEUTIANS TONIGHT.

.MODEL DISCUSSION...
SYNOPTICALLY...THE MODELS ARE IN DECENT AGREEMENT INTO SATURDAY WITH
THE MOVEMENT OF THE UPPER LOW CURRENTLY OVER THE EASTERN BERING SEA
AND SUBSEQUENT RIDGE BUILDING INTO THE GULF OF ALASKA SATURDAY INTO
SUNDAY. MAJOR DIFFERENCES START TO SHOW IN THE LATE WEEKEND TIME
FRAME AS AN UPPER LOW DEVELOPS OVER THE BERING SEA SUNDAY.

THE SURFACE LOW JUST SOUTH OF KODIAK TO MOVE UP INTO THE LOWER INLET
TONIGHT WILL RIDE JUST PAST ANCHORAGE INTO THE INTERIOR TOMORROW. IN
THE MEANTIME...THE SOUTHERLY FLOW WITH THE PARENT UPPER LOW IN THE
EASTERN BERING BRINGS SOME WARM AND MOIST AIR TO SOUTHCENTRAL AND
SOUTHEAST TONIGHT INTO TOMORROW. AN UPPER LEVEL DISTURBANCE TO RIDE
NORTH THROUGH SOUTHCENTRAL TONIGHT AND EARLY TOMORROW. COLD INTERIOR
AIR TO BE OVERRIDDEN WITH WARM AIR CREATING AREAS OF FREEZING
PRECIPITATION TONIGHT AND TOMORROW. SOME AREAS WILL SCOUR OUT TO ALL
RAIN TOMORROW ESPECIALLY ALONG THE COAST. HOWEVER...ALL AREAS WILL
START AS SNOW THIS AFTERNOON AND EVENING. AS THE LOW LIFTS NORTH AND
UPPER LOW SWINGS INLAND...MOST AREAS WILL RETURN TO SNOW FRIDAY
EVENING. THE UPPER LOW WILL SWING INLAND FRIDAY NIGHT PUSHING TO COLD
AIR ACROSS ALL OF SOUTHCENTRAL. AT THE BACKSIDE OF THE SURFACE
LOW...AN UPPER LEVEL DEFORMATION ZONE WILL CREATE AN AREA OF GOOD
SNOWFALL TONIGHT ALONG THE ALEUTIAN AND ALASKA RANGE. COLD AIR
ADVECTION THROUGHOUT THE BERING SEA WILL RESULT IN CONVECTIVE SNOW
SHOWERS THROUGHOUT TOMORROW. AN UPPER LOW MOVING OUT OF THE KAMCHATKA
REGION FRIDAY TO DIG A TROUGH SOUTH OF THE CENTRAL ALEUTIANS FRIDAY
NIGHT AND SATURDAY WITH THE COLD AIR FILTERING BEHIND THE UPPER LOW
THAT EXITED THE EASTERN BERING. THIS WRAPS INTO AN UPPER LOW SUNDAY.
BUT ENERGIES MOVING IN AND AROUND THIS FEATURE WILL BE A CAUSE FOR
UNCERTAINTY THROUGH MID NEXT WEEK. DURING THIS TIME...THE JET REMAINS
QUITE FAR SOUTH AROUND 40N.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...MOISTURE BEGINNING TO SPREAD OVER SOUTHCENTRAL
TONIGHT WITH PRECIP OVERRUNNING INTERIOR SITES FOR SNOW RIGHT NOW.
COLD DOME OF AIR OVER THE INTERIOR WITH PUSH OF WARM AIR TONIGHT WILL
CREATE AREAS OF FREEZING RAIN AND SLEET. SOME AREAS WILL REMAIN ALL
SNOW DURING THE EVENT. AS A DISTURBANCE MOVES NORTH THIS
EVENING...TURNAGAIN ARM WINDS WILL INCREASE. THIS WILL ERODE THE DOME
OF COLD AIR OVER ANCHORAGE SOMEWHAT ESPECIALLY NEAR THE ARM. IN
ADDITION...BLOWING SNOW WILL WORK INTO PORTAGE VALLEY AND EASTERN
TURNAGAIN ARM FOR A BIT.  AS IS TYPICAL IN THESE SCENARIOS...THE
LIKELIHOOD OF FREEZING RAIN IS HIGHER ALONG THE ARM AND SOUTH
ANCHORAGE FIRST. THE CONTINUED PUSH OF WARM AIR TOMORROW WILL RESULT
IN MANY AREAS EXPERIENCING FREEZING PRECIPITATION FROM SOUTHEAST
COPPER RIVER BASIN...MAT-SU VALLEY...ANCHORAGE...AND PARTS OF THE
KENAI PENINSULA. AREAS ALONG THE COAST WILL TURN TO ALL RAIN.  IN
FACT...CORDOVA WILL REMAIN MOSTLY RAIN THROUGH THE EVENT AND KODIAK
IS AND WILL REMAIN RAIN THROUGH TONIGHT.

.SOUTHWEST ALASKA...
SNOW WILL MOVE NORTH ALONG THE ALEUTIAN AND ALASKA RANGES TONIGHT
UNDER A DEFORMATION ZONE BETWEEN THE NEAR KODIAK SURFACE LOW AND
BRISTOL BAY UPPER LOW. THE UPPER LOW BECOMES STACKED WITH THE SURFACE
LOW FRIDAY INLAND OVER BRISTOL BAY WITH SOME DISTURBANCES ROTATING
AROUND SOUTHWEST ALASKA. THESE DISTURBANCES WILL CREATE SOME INTENSE
SNOW PERIODS AT TIMES FRIDAY NIGHT BEFORE THE LOW BEGINS TO LIFT
FURTHER INLAND. GAP WINDS ON THE BACKSIDE OF THE LOW WILL BE A
PROBLEM THROUGH FRIDAY ALONG THE AKPEN WITH THE COLD ADVECTION AND
WEST TO NORTHWEST FLOW. THE AFOREMENTIONED UPPER LOW THAT MOVES TO
THE CENTRAL ALEUTIANS FRIDAY WILL BRING A BRIEF WARM UP LATE IN THE
WEEKEND. SOME SHOWERS AND MODERATE WINDS WILL SKIRT THE AKPEN THROUGH
THE KUSKO COAST SATURDAY NIGHT AND SUNDAY.

.BERING SEA AND ALEUTIANS...
COLD ADVECTION OVER THE CENTRAL AND EASTERN BERING WITH OPEN WATER
MEANS CONVECTIVE SNOW SHOWERS. SOME CAN BE INTENSE AND BRING DOWN
VISIBILITIES IN A HURRY. A LOW WEST OF ATTU THIS AFTERNOON TO TRACK
SOUTH OF THE CHAIN THROUGH TOMORROW TO THE CENTRAL/EASTERN ALEUTIANS
FRIDAY NIGHT. MODERATE WINDS AND RAIN AND SNOW WILL ACCOMPANY THE
LOW. SOME WARMING CAN BE EXPECTED AHEAD OF THE LOW AS WELL. THE LOW
STALLS SOUTH OF THE EASTERN ALEUTIANS AS THE UPPER TROUGH DIGS AND A
RIDGE BUILDS IN THE GULF SUNDAY.

.LONG TERM FORECAST...MAJOR DIFFERENCES START TO SHOW IN THE LATE
WEEKEND TIME FRAME AS AN UPPER LOW DEVELOPS OVER THE BERING SEA
SUNDAY. PHASING AND STRENGTH OF DISTURBANCES THAT ARE FEEDING AND
MOVING AROUND THIS LOW ARE HANDLED DIFFERENTLY BY THE GFS AND ECMWF.
THEREFORE...FORECAST CONFIDENCE DROPS QUITE A BIT THROUGH NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...131
         WINTER WEATHER ADVISORY...101 111 121 125 141 145 152 161
MARINE...STORM WARNING...127 130
         GALE WARNING...120 125 128 131 132 139 140
                  150 155 160 165 172 174 176 177 178 179 180 181 185
         HEAVY FREEZING SPRAY...126 127 128 130 139 140
                                160 180 181 185
FIRE WEATHER...NONE.

JN NOV 13

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
119 AM AKST FRI NOV 22 2013

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

0125 AM     SNOW             KING SALMON             58.74N 156.54W
11/21/2013  E5.1 INCH                           AK   NWS EMPLOYEE

&&

KHOEPPNE