Small Craft Advisory 179, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
502 AM AKST WED FEB 25 2015

.ANALYSIS AND UPPER LEVELS...LOOKING FROM WEST TO EAST ON
SATELLITE THIS MORNING REVEALS THE THREE MAIN FEATURES QUITE
READILY. THE FIRST FEATURE IS A POTENT FRONTAL BOUNDARY DRAPED
ACROSS THE WESTERN ALEUTIANS. THIS BOUNDARY HAS BEEN SUPPORTED BY
A 80-100 KT JET IN THE UPPER LEVELS. THERE IS A SWATH OF GALE
FORCE WINDS WITHIN THIS FRONT STRETCHING FROM SHEMYA TOWARDS ADAK. IT
LOOKS LIKE IT IS GOING TO RECEIVE A REINFORCING SHOT OF UPPER
LEVEL ENERGY AS A 120-130 KT FINGER OF THE JET IS MOVING TOWARDS
IT FROM THE NORTH PACIFIC. THIS SAME JET IS HELPING TO STRETCH
SOME WARMER AIR IN THE MID TO UPPER LEVELS (18,000'-30,000') OVER
THE EASTERN BERING. THIS WARMER AIR IN TURN IS HELPING TO BUILD
HEIGHTS OVER THE AREA AND START TO USHER IN A RATHER IMPRESSIVE
RIDGE OVER THE SOUTHWEST PORTION OF THE STATE. MEANWHILE...THE
VERTICALLY STACKED LOW OVER THE GULF OF AK HAS "OUT-RUN" ITS
UPPER-LEVEL SUPPORT AND THUS...IS STARTING TO WEAKEN AT THE
SURFACE. IT IS STILL SWINGING A BROAD AREA OF MINIMUM FORCE GALE
WINDS THROUGH THE NORTHERN GULF AND STILL PUSHING SOME LIGHT RAIN
INTO KODIAK. AS THE LOW PULLS FURTHER TO THE EAST LATER
TODAY...RAIN SHOULD SLOWLY END FOR KODIAK. AS THE RIDGE BUILDS IN
OVER THE MAINLAND THOUGH...A MODEST NORTH TO SOUTH GRADIENT WILL
START TO ESTABLISH ITSELF WITH SOME COLDER AIR UNDER THE SURFACE
HIGH BEING PULLED INTO THE WEAKENING LOW IN THE GULF. THIS SHOULD
RESULT IN SOME GUSTIER WINDS FOR THE TYPICAL OUTFLOW LOCATIONS
SUCH AS WHITTER...THOMPSON PASS...SEWARD AND THE COPPER RIVER
DELTA.

&&

.MODEL DISCUSSION...PRETTY STRONG AGREEMENT AMONGST THE MODELS IN
THE NEAR TERM...ESPECIALLY HANDLING THE RIDGE BUILDING OVER THE
MAINLAND AND THE LOW IN THE GULF. THUS...FORECAST UTILIZED MOSTLY
THE HIGHER RESOLUTION MODELS (GEM REGIONAL) IN THOSE AREAS.
REGARDING THE WEAK LOW THAT TRIES TO FORM ALONG THE FRONT OVER THE
WESTERN/CENTRAL ALEUTIANS THURSDAY INTO FRIDAY...THE FORECAST WAS
TIPPED IN FAVOR OF AN EC/GFS BLEND. THIS KEPT A BROAD BRUSHED
APPROACH TO WHAT LOOKS TO BE A VERY WEAK SYSTEM THAT WILL HAVE
LITTLE IMPACT OVER THE WESTERN BERING.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
DRY CONDITIONS ARE EXPECTED ACROSS SOUTH CENTRAL ALASKA FOR THE
NEXT COUPLE OF DAYS AS AN UPPER LEVEL RIDGE BUILDS OVER THE AREA.
THE EXCEPTION IS SOME SHOWERS OVER KODIAK THIS MORNING BEFORE THE
LOW IN THE GULF MOVES TOO FAR EAST. AS THIS LOW MOVES EAST LATER
TODAY...OFFSHORE WINDS WILL INCREASE IN FAVORED AREAS. WITHOUT
MUCH IN THE WAY OF COLD ADVECTION AND BEING MAINLY GRADIENT
DRIVEN...THE WINDS WILL NOT BE VERY STRONG OR WIDESPREAD.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE WILL DOMINATE THE WEATHER ACROSS SOUTHWEST THROUGH
THURSDAY. AS THE PRESSURE GRADIENT SLACKENS AND NORTHERLY OFFSHORE
WINDS DIMINISH...PATCHY OVERNIGHT FOG WILL BECOME MORE
PREVALENT...ESPECIALLY ACROSS THE LOWER KUSKOKWIM VALLEY AND
BRISTOL BAY. A STALLED FRONT OVER THE CENTRAL BERING WILL KEEP
STRONGER SOUTHERLY FLOW OVER THE KUSKOKWIM DELTA...THUS LIMITING
FOG POTENTIAL BEYOND THIS MORNING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

A SLOW MOVING FRONTAL ZONE OVER THE WESTERN BERING AND ALEUTIANS
WILL CONTINUE TO BRING CLOUDS AND PRECIPITATION FROM THE NORTH
PACIFIC...AS WELL AS GALE FORCE SOUTHERLY WINDS. THIS FRONT WILL
TRACK EAST TOWARD THE CENTRAL ALEUTIANS THROUGH THURSDAY.
OTHERWISE...THE EASTERN ALEUTIAN AND PRIBILOF ISLANDS WILL SEE
GENERALLY QUIET AND DRY WEATHER AS HIGH PRESSURE HOLDS OVER THE
EASTERN BERING.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
WITH A STRONG RIDGE ALOFT STRETCHING FROM THE GULF OF ALASKA
ACROSS SOUTH CENTRAL ALASKA...THE NEXT FRONTAL SYSTEM WILL TRACK
NORTH FROM THE NORTH PACIFIC UP TOWARDS THE ALASKA PENINSULA ON
FRIDAY. THIS SYSTEM WITH AN ACCOMPANYING SHORTWAVE TROUGH WILL
TURN NORTHEASTWARD REACHING KODIAK ISLAND FRIDAY NIGHT BEFORE
WEAKENING AS IT CONTINUES TOWARDS COOK INLET AND THE KENAI
PENINSULA SATURDAY.

A STRONGER SHORTWAVE TROUGH FROM THE WEST BRINGING A GOOD SUPPLY
OF COLD AIR AND SNOW SHOWERS WITH IT WILL REACH THE WEST COAST OF
ALASKA SATURDAY MORNING THEN CONTINUE RAPIDLY EAST REACHING SOUTH
CENTRAL ALASKA SATURDAY EVENING. THE COLD AIR AND LIFT FROM THIS
SHORTWAVE COMBINED WITH THE MOISTURE FROM THE WEAKENING FRONTAL
SYSTEM WILL COME TOGETHER TO PRODUCE A GOOD CHANCE FOR SNOW FOR
MUCH OF SOUTH CENTRAL ALASKA SATURDAY AFTERNOON THROUGH SATURDAY
EVENING. RIDGING WILL REBUILD RAPIDLY SUNDAY BRINGING DRIER SUNNY
WEATHER AGAIN BEFORE THE NEXT FRONTAL SYSTEM REACHES SOUTHWEST
ALASKA MONDAY AFTERNOON OR EVENING.

FURTHER WEST IN THE ALEUTIANS...A STRONG FRONTAL SYSTEM WILL
APPROACH THE WESTERN END OF THE CHAIN FRIDAY NIGHT THEN CONTINUE
EAST SATURDAY AND SUNDAY AS THE PARENT LOW SWINGS PAST SHEMYA AND
LIFTS NORTH INTO THE WESTERN BERING. THE NEXT FRONTAL SYSTEM WILL
REACH THE WESTERN ALEUTIANS MONDAY NIGHT OR TUESDAY TAKING A
QUICKER MORE EAST NORTHEAST TRACK INTO THE BERING TUESDAY NIGHT
AND WEDNESDAY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 132 175 176 177 178 185 352 411 412 413.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MSO
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...JER