Small Craft Advisory 124, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
429 PM AKST MON FEB 9 2015

.ANALYSIS AND UPPER LEVELS...
THERE IS AN INVERTED UPPER TROUGH OVER THE CENTRAL ALEUTIANS WITH
AN ASSOCIATED SURFACE LOW SOUTH OF THE ALASKA PENINSULA AND A
FRONT STRETCHING FROM THE EASTERN ALEUTIANS THROUGH KODIAK ISLAND
AND ALONG THE GULF COAST. THERE IS AN UPPER LEVEL HIGH OVER THE
WESTERN BERING AND ANOTHER OVER THE EASTERN GULF EXTENDING
SOUTHEASTWARD. THE FRONT IS OCCLUDED FROM THE EASTERN ALEUTIANS
THROUGH THE ALASKA PENINSULA AND IS A WARM FRONT FROM KODIAK
THROUGH THE GULF COAST. THE COLD FRONT PORTION EXTENDS SOUTHEAST
FROM ABOUT CHIGNIK INTO THE NORTH PACIFIC.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT IN THE SHORT
TERM. THE CANADIAN MODELS (REGIONAL AND NORTHERN HEMISPHERE) ARE
A LITTLE DIFFERENT FROM THE OTHER MODELS IN HOW THEY HANDLE A LOW
IN THE GULF TUESDAY AFTERNOON/EVENING AND THEY WERE NOT USED FOR
THE AFTERNOON FORECAST. PREFERENCE WAS FOR THE NAM FOR THE FIRST
DAY OR TWO...THEN TRANSITIONING TOWARD THE ECMWF. FORECAST
CONFIDENCE IS LOWERED A LITTLE BIT DUE TO THE PATTERN
CHANGE...AND IS NEAR TO ABOVE NORMAL.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
EXPECTING SOME SNOW THROUGH THE COOK INLET AREA TONIGHT WITH THE
INITIAL ARRIVAL OF THE WARM FRONT. THIS SHOULD NOT AMOUNT TO
MUCH...BUT WITH THE OVER-RUNNING OF MOIST AIR OVER THE COLD AND
DRY SURFACE AIR IT SHOULD BE A HIGH POP/LOW QPF EVENT. AS FLOW
BECOMES MORE EASTERLY LATER TONIGHT ANY SNOW SHOULD CUT BACK TO
ISOLATED SHOWERS. WARMER AIR IS ALREADY SURGING INTO KODIAK ISLAND
BUT WILL STALL THERE THROUGH TUESDAY NIGHT...THEN SLOWLY WORK ITS
WAY NORTH ON WEDNESDAY THROUGH THE GULF COAST.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK UPPER TROUGH WILL LIFT NORTHWARD THROUGH THE KUSKOKWIM
DELTA AND LOWER KUSKOKWIM VALLEY TODAY...WITH A FRONTAL SYSTEM
PUSHING INTO THE BRISTOL BAY REGION. MAINLY THE THE KUSKOKWIM
VALLEY AND DELTA WILL SEE AN INCREASE IN CLOUD COVER OVERNIGHT
TONIGHT THROUGH TOMORROW...AS THE WAVE DISSIPATES OVERHEAD. A
CHANCE FOR SNOW AND RAIN WILL PERSIST ACROSS BRISTOL BAY INTO THE
MIDDLE OF THE WEEK...AS A NORTH PACIFIC FRONT CROSSES THE ALASKA
PENINSULA AND EVENTUALLY STALLS AND WEAKENS OVER THE SOUTHEASTERN
BERING. OTHER AREAS AROUND THE THE SOUTHWEST MAINLAND WILL REMAIN
GENERALLY DRY...WITH GUSTY AND PERSISTENT NORTHEASTERLY OFFSHORE
FLOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A FRONT CURRENTLY TRACKING INTO THE THE ALASKA PENINSULA AND
EASTERN ALEUTIANS WILL BRING ABUNDANT PRECIPITATION AND GUSTY
WINDS TO THE SOUTHEASTERN BERING OVER THE COMING DAYS AS IT STALLS
AND GRADUALLY WEAKENS. AREAS OF BLOWING SNOW WILL PERSIST ALONG
THE PARTS OF THE ALASKA PENINSULA AND EASTERN ALEUTIANS THROUGH
EARLY THIS EVENING AS THE FRONT CONTINUES TO TRACK INTO THE
REGION. TEMPERATURES WILL BEGIN TO WARM MORE DRAMATICALLY THIS
EVENING...TRANSITIONING FROM SNOW TO RAIN...THUS GETTING RID OF ANY
BLOWING SNOW CONCERNS. MEANWHILE...A TIGHT PRESSURE GRADIENT
BETWEEN HIGH PRESSURE NEAR THE KAMCHATKA PENINSULA AND AN UPPER
LOW OVER THE NORTH PACIFIC WILL HELP TO MAINTAIN GUSTY GALE FORCE
WINDS ACROSS MUCH OF THE CENTRAL BERING THROUGH THE MIDDLE OF THE
WEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...SOUTHERLY FLOW BETWEEN A
LARGE UPPER LEVEL RIDGE OVER THE WESTERN US AND CANADA AND A BROAD
UPPER LEVEL LOW CENTERED SOUTH OF THE TIP OF THE ALASKA PENINSULA
WILL BRING A SERIES OF FRONTAL WAVES INTO THE GULF OF ALASKA FROM
MIDWEEK THROUGH AROUND SATURDAY. WITH THE POSITION OF THE UPPER
RIDGE AXIS INLAND OVER CANADA AND THE CORE OF THE SOUTH TO NORTH
RUNNING JET ALONG THE WEST SIDE OF THE RIDGE OVER THE FAR EASTERN
GULF AND SOUTHEAST ALASKA...THE WARMEST AND MOISTEST OF THE
SOUTHERLY FLOW SHOULD REMAIN EAST OF THE AREA. HOWEVER EVEN WITH
THE MORE MODERATE OVERRUNNING...THE LARGE NUMBER OF FRONTAL WAVES
PUSHING UP OVER THE AREA WILL STILL BRING A DEFINITE WARMING
TREND WITH NUMEROUS OPPORTUNITIES FOR PRECIPITATION. CURRENTLY
PRECIPITATION TYPES ARE LOOKING TO BE PREDOMINATELY RAIN
IMMEDIATELY ALONG THE GULF COAST CHANGING OVER TO SNOW NOT FAR
INLAND. AS THE WARMING PROGRESSES THROUGH THE END OF THE WEEK SOME
ISOLATED FREEZING RAIN MAY STILL BE POSSIBLE IN COLD WIND
SHELTERED VALLEYS OR WINDY ONES DRAWING AIR DIRECTLY FROM THE
INTERIOR. OVERALL...THE POTENTIAL FOR WIDESPREAD IMPACTS FROM
MIXED PRECIPITATION TYPES CONTINUES TO BE TRENDING GRADUALLY DOWN
FROM PREVIOUS MODEL RUNS.

IN THE MORE EXTENDED TIME PERIODS MODELS ARE NOW SUGGESTING A
SECOND PATTERN SHIFT WITH A LARGE NEGATIVELY TILTED UPPER LEVEL
RIDGE BUILDING OVER THE GULF OF ALASKA AROUND SUNDAY WITH A COUPLE
OF STRONG LOWS SPINNING UP ALONG ITS SOUTHWEST SIDE AND TRACKING
TO THE WEST SOUTHWEST BETWEEN 40N AND 50N SOUTH OF THE ALEUTIANS.
FOR SOUTHCENTRAL ALASKA THE POSITION OF THIS RIDGE WOULD START A
DRYING TREND WHILE WARM AND PERIODICALLY WET SOUTHEASTERLY FLOW
WOULD BE DIRECTED AT KODIAK ISLAND AND SOUTHWEST ALASKA AS WELL AS
THE ALASKA PENINSULA WITH VARIOUS SURFACE LOWS TRACKING WEST DOWN
THE ALEUTIANS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 138
         GALE 119 120 127 130 131 132 136 137 139 150 155
         160 165 170 171 172 173 174 175 176 177 179 180
         181 185
         HEAVY FREEZING SPRAY 127 139 179 180 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP
LONG TERM...JR