Small Craft Advisory 265, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
424 PM AKDT WED MAR 25 2015

.ANALYSIS AND UPPER LEVELS...

A BROAD LONGWAVE TROUGH REMAINS IN CONTROL ACROSS MUCH OF THE
NORTHERN PACIFIC. THE MAIN FEATURE WITHIN THIS OVERALL PATTERN IS
A VERTICALLY STACKED LOW SPINNING ABOUT 300 MILES SOUTH OF KODIAK
ISLAND. THIS LOW IS DRIFTING SLOWLY NORTHWARD...WITH AN ASSOCIATED
FRONT DRAPED ACROSS KODIAK ISLAND AND UP ALONG THE NORTH GULF
COAST. A SEASONABLY STRONG 130 KT JET IS CLIMBING OUT OF THE BASE
OF THIS TROUGH AND HEADING INTO THE PANHANDLE...AND FOR ALL
INTENTS AND PURPOSES IS NOW TOO FAR EAST TO IMPART ANY ADDITIONAL
ENERGY TO THE AFOREMENTIONED LOW SOUTH OF KODIAK. AS A
RESULT...THE STORM IS NOW ENTERING ITS WEAKENING PHASE.

THIS STORM HAS DISLODGED THE HIGH PRESSURE THAT HAD BEEN IN
CONTROL OF SOUTHERN ALASKA WEATHER FOR THE LAST FEW DAYS...AND IN
FACT THE STRENGTH AND PERSISTENCE OF THIS HIGH PRESSURE PATTERN IS
WHAT IS ALLOWING WINDS TO BE A LITTLE STRONGER WITH THIS FRONT
THAN WE TYPICALLY SEE WITH A LOW IN THE 970S MB RANGE. STORM FORCE
WINDS ARE BEING OBSERVED FROM THE BARREN ISLANDS DOWN SHELIKOF
STRAIT...WITH A BROAD AREA OF GALE FORCE WINDS ACROSS MUCH OF THE
GULF AND KODIAK ISLAND. INLAND AREAS REMAIN DRY...THOUGH MID AND
HIGH CLOUDS ARE GRADUALLY EXPANDING NORTHWARD ACROSS THE
POPULATION CENTERS. GUSTY NORTHEAST WINDS THROUGH THE MATANUSKA
VALLEY ARE ALREADY MIXING DOWN TO THE SURFACE...WITH RELATIVE
HUMIDITY VALUES DROPPING AS EXPECTED. A RED FLAG WARNING REMAINS
IN EFFECT THROUGH THIS EVENING.

TO THE WEST...RADAR IMAGERY SHOWS A FAIR AMOUNT OF RETURNS OVER
THE BRISTOL BAY AREA...BUT THE VAST MAJORITY OF THIS PRECIP IS NOT
REACHING THE GROUND AS GUSTY OFFSHORE FLOW CONTINUES TO RESUPPLY
DRY AIR AT THE LOWEST LEVELS OF THE ATMOSPHERE. THE WESTERN EDGE
OF THIS STORM SYSTEM IS NEARLY STATIONARY NEAR AND EAST OF THE
PRIBILOF ISLANDS WITH WINDS AND FALLING SNOW SIGNIFICANTLY
REDUCING VISIBILITIES.

&&

.MODEL DISCUSSION...

THE MODELS REMAIN IN GOOD SYNOPTIC AGREEMENT. AS THE UPPER LEVEL
LOW SOUTH OF KODIAK ISLAND WEAKENS SIGNIFICANTLY THIS
EVENING...THE WEAKENING SURFACE LOW WILL LIKELY CONTINUE NORTHWARD
AND THE SYSTEM WILL CEASE TO BE VERTICALLY STACKED. THE EXACT
TRACK OF THE WEAKENING SURFACE LOW WILL BE HIGHLY SENSITIVE TO THE
EXACT TIMING/RATE OF WEAKENING OF THE CORRESPONDING UPPER
CIRCULATION. THE GFS IS ON THE SOUTH END OF THE SCALE...AND PASSES
THE LOW OVER THE SOUTH END OF KODIAK ISLAND TONIGHT...WHILE THE
ECMWF IS THE OTHER END OF THE SCALE AND TAKES THE LOW OVER
NORTHERN KODIAK ISLAND AND INTO EXTREME SOUTHERN COOK INLET. THE
NAM AND GEM ARE SOMEWHERE IN THE MIDDLE...BUT CLOSER TO THE
NORTHERN SOLUTION. THE MAIN REASON THIS DISCREPANCY IS IMPORTANT
IS BECAUSE IT WILL AFFECT HOW STRONG THE SOUTHEAST WINDS AROUND
ANCHORAGE AND THE MATANUSKA VALLEY WILL BE TOMORROW. CURRENT
FORECAST IS MORE TOWARD THE NORTHERN END OF THIS SPECTRUM...AND
WITH EACH MODEL MORE-OR-LESS HOLDING ITS GROUND...WILL STICK
PRETTY CLOSE TO THE INHERITED FORECAST FOR THE AFTERNOON FORECAST
PACKAGE. OVERALL FORECAST CONFIDENCE REMAINS NEAR OR SLIGHTLY
ABOVE NORMAL.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

THE LEADING PORTION OF A WELL WRAPPED OCCLUDED FRONT WILL BRING
STRONG WINDS TO THE NORTH GULF COAST THIS EVENING. SOME OF THESE
WINDS ARE AFFECTING THE MATANUSKA VALLEY WITH RED FLAG CRITERIA IN
THE RANGE OF 25 PERCENT RH AND 25 MPH WINDS. RH VALUES WILL
RECOVER THIS EVENING AND ALLOW TO WARNING TO EXPIRE.

THE FRONT WILL BE ACCOMPANIED BY RAIN ALONG THE COAST TONIGHT WITH
SOME SHOWERS CROSSING THE CHUGACH AND KENAI MOUNTAINS...ALTHOUGH
DOWNSLOPING WILL KEEP THESE SHOWERS TO A MINIMUM. ON THU THE LOW
AND REMAINDER OF THE OCCLUDED FRONT WILL MOVE OVER KODIAK ISLAND.
THIS WILL CAUSE WINDS TO BECOME MORE SOUTHERLY AND LESSEN THE
DOWNSLOPING EFFECT. IN ADDITION IT WILL ALLOW SOUTHEAST WINDS OUT
OF THE KNIK RIVER VALLEY TO DEVELOP AND LOWER RH VALUES INTO THE
UPPER 30 PERCENT RANGE THU AFTERNOON. BY FRIDAY MOIST SOUTHERLY
FLOW WILL CONTINUE SHOWER ACTIVITY ACROSS SOUTHCENTRAL.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE VERTICALLY STACKED LOW SOUTH OF KODIAK ISLAND WILL CONTINUE
TO WEAKEN AND TRACK NORTHWARD INTO THE ALASKA PENINSULA
OVERNIGHT...BEFORE FURTHER WEAKENING AS IT CROSSES OVER THE
ALEUTIAN RANGE AND INTO THE BRISTOL BAY ZONE TOMORROW. SCATTERED
RAIN AND SNOW SHOWERS REMAIN CONFINED MOSTLY TO THE COASTAL AREAS
OF THE KUSKOKWIM DELTA AND BRISTOL BAY ZONE...WITH MUCH OF THE
INTERIOR OF BRISTOL BAY REMAINING DOWNSLOPED AND DRY WITH GUSTY
EASTERLY WINDS. SCATTERED RAIN AND SNOW SHOWERS WILL BEGIN TO FILL
IN OVER THE BRISTOL BAY AREA TOMORROW AFTERNOON...AS THE REMNANTS
OF THE AFOREMENTIONED LOW CROSSES OVER INTO THE BRISTOL BAY ZONE.
THESE SHOWERS WILL SPREAD INTO THE KUSKOKWIM DELTA AND KUSKOKWIM
VALLEY BY FRIDAY...AS THE WAVE CONTINUES TO PROGRESS NORTHWARD.
DESPITE THE INCREASED CLOUD COVER OVER THE MAINLAND...PARTS OF THE
SOUTHWEST MAINLAND WILL CONTINUE TO SEE ABOVE NORMAL TEMPERATURES
THROUGH THE END OF THE WEEK.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A WEAKENING FRONTAL BOUNDARY CONTINUES TO TRACK THROUGH THE
EASTERN BERING THIS EVENING...WITH PERSISTENT AND GUSTY NORTHERLY
FLOW PRODUCING RAIN AND SNOW SHOWERS OVER THE EASTERN PORTION OF
THE ALEUTIANS AND BERING. BLOWING SNOW WILL REMAIN A THREAT OVER
THE PRIBILOF ISLANDS THROUGH TOMORROW AFTERNOON...WITH REDUCED
VISIBILITIES TO ONE MILE OR LESS AT TIMES. SNOW SHOWERS OVER THE
AREA WILL BEGIN TO TAPER OFF TOMORROW AFTERNOON ENDING THE BLOWING
SNOW THREAT FOR THE PRIBILOF ISLAND. HOWEVER...GUSTY WINDS OVER
THE EASTERN/CENTRAL BERING AND ALEUTIANS WILL PERSIST THROUGH THE
END OF THE WEEK. FURTHER WEST...HIGH PRESSURE ALONG WITH SOME
LINGERING SNOW SHOWERS WILL REMAIN OVER THE WESTERN PORTION OF THE
BERING AND ALEUTIANS THROUGH THE END OF THE WEEK.

&&

.LONG TERM FORECAST (SATURDAY THROUGH WEDNESDAY)...
THE SECOND GALE FORCE NORTH PACIFIC LOW WILL TRACK SOUTH OF KODIAK
ISLAND BY SATURDAY MORNING. THE ASSOCIATED WEATHER FRONT WITH THIS
SYSTEM WILL BE LOCATED FROM KODIAK ISLAND NORTHWARD ALONG THE
NORTHERN GULF COASTLINE. THIS WILL BRING WIDESPREAD RAIN MAINLY
ALONG THE COAST BUT SOME RAIN SHOWERS WILL MAKE IT OVER THE
CHUGACH MOUNTAINS INTO THE ANCHORAGE BOWL. OTHERWISE...THE MATSVALLEY
AND THE ANCHORAGE BOWL WILL DOWNSLOPE RESULTING IN DRIER
CONDITIONS THROUGH THE WEEKEND. THIS LOW PRESSURE SYSTEM WILL
SLOWLY MOVE TO THE NORTHERN GULF BY MONDAY AND BECOME STATIONARY
BEFORE DISSIPATING BY LATE TUESDAY. THIS SYSTEM WILL CONTINUE TO
BRING WARM TEMPERATURES AND PRECIPITATION ALL IN THE FORM OF RAIN
ALONG THE COASTAL REGION THROUGH WEDNESDAY. THE CHUGACH AND KENAI
MOUNTAINS WILL AGAIN KEEP MAJORITY OF INLAND AREAS DRY EXCEPT FOR
SOME SLOP-OVER RAIN SHOWERS MAKING IT OVER THE MOUNTAINS BEFORE
THE LOW DISSIPATES BY LATE TUESDAY.

THE BERING SEA AND THE ALEUTIANS...REMAIN IN PERSISTENT NORTHERLY
FLOW THROUGH THE WEEKEND. THE EASTERN BERING SEA/ALEUTIANS AND THE
BRISTOL BAY AREA WILL RECEIVE THE EFFECTS FROM THE NORTH PACIFIC
LOW AS IT MOVES NEAR KODIAK ISLAND. THE PRECIPITATION WILL SPREAD
OVER INTO THE EASTERN BERING SEA/ALEUTIANS THROUGH THE WEEK. BY
SATURDAY THE NEXT NORTH PACIFIC LOW TRACKS TOWARDS KODIAK ISLAND.
THIS WILL CONTINUE TO BRING WARMER TEMPERATURES AND RAIN ALONG
THE EASTERN ALEUTAINS AND THE BRISTOL BAY AREA. BY MONDAY A SERIES
OF WEAK WAVES WILL ENTER THE WESTERN ALEUTIANS AND MOVE ALONG THE
CHAIN TO THE EASTERN ALEUTIANS BY WEDNESDAY. THIS WILL BRING
WARMER TEMPERATURES WITH RAIN...WHICH WILL SPILL OVER INTO THE
LOWER BERING SEA AS THE LOW TRACKS EASTWARD THROUGH THE MIDDLE OF
NEXT WEEK. FARTHER NORTH IN THE BERING THEY WILL SEE A WINTRY MIX
DUE TO THE COOLER TEMPERATURES.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORMS 130 131. GALES 119 120 125 138 139. HEAVY
FREEZING SPRAY 179.
FIRE WEATHER...RED FLAG WARNING ZONE 111.

&&

SYNOPSIS AND MODEL DISCUSSION...AD
SOUTHCENTRAL ALASKA...DY
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP
LONG TERM...PD