Small Craft Advisory 912, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
330 PM AKST SAT NOV 15 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN CONTINUES TO BE DOMINATED BY THE BLOCKING
RIDGE ALONG THE WEST COAST OF NORTH AMERICA INTO THE YUKON
TERRITORY AND UPPER LEVEL LOWS OVER THE KAMCHATKA PENINSULA TO THE
EASTERN ALEUTIANS. THERE ARE MULTIPLE SURFACE LOWS ACROSS THE
REGION...FROM THE THE SOUTHERN KAMCHATKA PENINSULA TO THE WESTERN
BERING SEA TO SOUTH OF THE EASTERN ALEUTIANS TO SOUTH OF THE GULF
OF ALASKA. STRONG HIGH PRESSURE PERSISTS FROM BRITISH COLUMBIA TO
THE YUKON TERRITORY. STRONG SURFACE INVERSIONS ARE PREVALENT
ACROSS THE SOUTH CENTRAL REGION DUE TO RADIATIONAL COOLING
OVERNIGHT AND THE VERY WARM AIR ALOFT.

&&

.MODEL DISCUSSION...
MODELS ARE IN VERY GOOD AGREEMENT IN THE SHORT TERM. MINOR
DIFFERENCES ARISE AT THE 24 HOUR FORECAST TIME FOR THE MODERATE
STRENGTH LOW APPROACHING THE CENTRAL ALEUTIANS SUN NIGHT. THE NAM
IS THE OUTLIER AND A BLEND OF THE ECMWF AND GFS WILL BE USED FOR
THIS SYSTEM.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
DRY CONDITIONS WILL PERSIST ACROSS MUCH OF SOUTHCENTRAL ALASKA
THROUGH SUNDAY MORNING DUE TO THE PRESENCE OF THE STRONG BLOCKING
HIGH JUST TO THE EAST. OVERNIGHT TONIGHT AND THROUGH SUNDAY WAVES
MOVING UP TO THE GULF COAST AND KODIAK ISLAND IN THE SOUTHEAST
FLOW WILL BRING CLOUDS AND RAIN TO THESE AREAS. CLOUDS WILL SPREAD
NORTH UP COOK INLET SUNDAY AND INTO THE SUSITNA VALLEY SUNDAY
NIGHT INTO MONDAY. FOG ISSUES WILL PERSIST IN THE COPPER RIVER
BASIN THROUGH SUNDAY NIGHT DUE TO THE STRONG INVERSION. THE FOG
CONCERNS FOR NORTHERN COOK INLET WILL LESSEN DUE TO THE INCREASED
CLOUD COVER AND INCREASED MIXING FROM THE TIGHTENING GRADIENT AS
THE FIRST WAVE MOVES UP FROM THE GULF THIS EVENING. BY SUNDAY
NIGHT SOME LIGHT RAIN IS POSSIBLE OVER THE NORTHERN COOK INLET
REGION. THE COLD SOAKED GROUND WILL LIKELY RESULT IN THE RAIN
INITIALLY FREEZING ON CONTACT IN ISOLATED AREAS OF EAST ANCHORAGE
AND UP INTO THE PALMER WASILLA AREA. THE STRONG SOUTHEAST FLOW
ACROSS THE CHUGACH MOUNTAINS WILL RESULT IN THE TYPICAL DOWNSLOPE
PRECIPITATION SHADOW ON THE LEEWARD SIDE OF THE
MOUNTAINS...MEANING WHAT DOES FALL WILL BE VERY LIGHT.
MEANWHILE...THE UPSLOPE SIDE OF THE COASTAL MOUNTAINS WILL SEE A
RETURN TO STEADY RAIN BY SUNDAY AFTERNOON. KODIAK ISLAND WILL
CONTINUE TO SEE THE BRUNT OF RAIN AND WIND WITH ONLY VERY BRIEF
BREAKS IN INTENSITY BETWEEN WAVES.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A FAST MOVING WAVE WILL MOVE ACROSS THE ALASKA PENINSULA THIS
EVENING IN THE PERSISTENT SOUTHEAST FLOW. THIS WILL INCREASE THE
PRESSURE GRADIENT RESULTING IN INCREASED WIND ACROSS THE ALEUTIAN
MOUNTAINS THROUGH THIS EVENING. THE DOWNSLOPE FLOW WILL RESULT IN
A BIT OF A RAIN SHADOW ON THE LEEWARD SIDE OF THE ALEUTIAN
MOUNTAINS AND THE MORE PERSISTENT RAIN WILL FALL ALONG THE KILBUCK
MOUNTAINS. MOISTURE WILL PUSH ACROSS THE KUSKOKWIM DELTA IN THE
SOUTHEAST FLOW. THE PERSISTENT WARM AIR FLOW ACROSS THE REGION
WILL KEEP PRECIPITATION LIQUID.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE LOW SOUTH OF THE EASTERN ALEUTIANS WILL SLOWLY MOVE NORTH
ACROSS THE EASTERN ALEUTIANS BY SUNDAY MORNING. THE UPPER LEVEL
LOW ANCHORED OVER THE SOUTHERN KAMCHATKA PENINSULA WILL HOLD THE
MOIST WARM SOUTHERLY FLOW OVER THE ALEUTIANS AND WESTERN BERING
SEA THROUGH MONDAY. AN INTENSIFYING LOW WILL MOVE TOWARD THE
CENTRAL ALEUTIANS SUNDAY NIGHT TO MONDAY MORNING TIME FRAME. THE
MODELS ARE NOT CONSISTENT ABOUT THE INTENSITY AND LOCATION OF THIS
STORM. THE CURRENT THINKING IS IT WILL INTENSIFY AS IT MOVES INTO
THE CENTRAL ALEUTIANS BRINGING WITH IT GALE FORCE WINDS AND
WIDESPREAD RAIN AS IT APPROACHES.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE BLOCKING PATTERN WILL REMAIN FOR THE NEXT WEEK WITH HIGH
PRESSURE HOLDING STRONG OVER THE EASTERN PART OF THE STATE. A
BROAD UPPER LEVEL LOW WILL ALSO STAY OVER THE BERING DURING THIS
TIME. WHILE IN THIS PATTERN A COUPLE FRONTS ARE EXPECTED TO MOVE
INTO THE AREA FROM THE SOUTH. THE FIRST WILL BE ON TUESDAY WHICH
WILL BRING MORE PRECIPITATION TO PORTIONS OF SOUTHWEST AND
SOUTHCENTRAL ALASKA. THE SECOND WILL BE THURSDAY NIGHT...HOWEVER
THERE IS MORE UNCERTAINTY WITH THIS SYSTEM AS THERE IS LARGE
DISAGREEMENT BETWEEN THE MODELS FOR THIS TIME PERIOD.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 119 120 130 131 138 139 150 155 174 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SA
SOUTHCENTRAL ALASKA...SA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SA
LONG TERM...DK