Small Craft Advisory 150, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
444 PM AKST MON FEB 16 2015

.ANALYSIS AND UPPER LEVELS...

LARGE AND BROAD CYCLONIC CIRCULATION DOMINATES THE ANCHORAGE AREA
OF RESPONSIBILITY CURRENTLY...WITH THE PRIMARY FEATURE ATTACHED TO
A 971 MB SURFACE LOW NEAR THE SOUTHERN TIP OF THE ALASKA
PENINSULA. A STORM FORCE FRONT WITH A STRONG UPPER LEVEL SHORTWAVE
DISTURBANCE...AND A DEVELOPING TRIPLE POINT LOW NEAR THE NORTHERN
ALASKA PENINSULA...ARE MOVING INLAND OVER SOUTHCENTRAL AND
SOUTHWEST ALASKA THIS AFTERNOON. AS IS TYPICALLY THE CASE WITH A
STRENGTHENING SYSTEM MOVING INLAND AND STRONG GEOSTROPHIC FLOW AT
MOUNTAINTOP LEVEL...PRECIPITATION HAS BEEN A BIT HEAVIER THAN
ANTICIPATED ALONG THE WESTERN SLOPES OF THE CHUGACH
RANGE...FALLING MAINLY IN THE FORM OF RAIN BUT OCCASIONALLY MIXED
WITH A FEW SNOWFLAKES AND ICE PELLETS.

THE WINDS HAVE ALSO BEEN A BIT STRONGER THAN INITIALLY
ANTICIPATED...PARTICULARLY ALONG THE COAST FROM THE BARREN ISLANDS
NORTH AND EAST WHERE HURRICANE FORCE WINDS HAVE BEEN RECORDED.

&&

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT SYNOPTICALLY. THE LARGE CYCLONIC
CIRCULATION OVER THE SOUTHERN TIP OF THE ALASKA PENINSULA WILL
PUSH NORTH ACROSS THE WESTERN COAST OF THE STATE...SETTING UP
BROAD SOUTHERLY UPPER LEVEL FLOW WHICH WILL PUSH WEAK
DISTURBANCES NORTH FROM THE NORTH PACIFIC INTO THE MAINLAND.
HIGHLY AMPLIFIED RIDGING WILL BECOME STATIONARY OVER THE PANHANDLE
AND WESTERN CANADA LATE THIS WEEK THROUGH THE WEEKEND WHICH WILL
BRING CONTINUED ABNORMALLY WARM AND SOMEWHAT STORMY CONDITIONS FOR
MOST OF THE ANCHORAGE AREA OF RESPONSIBILITY.

&&

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

THE WEAKENING NORTH PACIFIC STORM WILL CONTINUE TO RAIN AND WARM
TEMPERATURES TO MUCH OF SOUTHCENTRAL THROUGH THIS EVENING. THE
STRONG GAP WINDS ALONG TURNAGAIN ARM AND KNIK ARM WILL ALSO
CONTINUE AS THE STORM FORCE BARRIER JET REMAINS OVER THE GULF
COAST THIS EVENING. GUSTY SOUTHEASTERLY WINDS ARE STILL EXPECTED
TO BRIEFLY PUSH INTO THE LOWER ELEVATIONS OF THE ANCHORAGE BOWL
THIS EVENING AS THE UPPER LEVEL SHORT WAVE PASSES OVERHEAD...AND
THEN QUICKLY DIMINISH BY LATE THIS EVENING AS THE SHORTWAVE AND
WINDS ALOFT MOVE OUT OF THE AREA. AS IS EVIDENT ON THE 3000 FT
FREEZING LEVEL FROM THE ANCHORAGE SOUNDING THIS
AFTERNOON...PRECIPITATION FROM THIS SYSTEM SHOULD SAFELY REMAIN IN
THE FORM OF RAIN BUT WILL BE MOSTLY BE LIMITED TO THE GULF COAST
AND SUSITNA VALLEY WITH DOWNSLOPING PREVAILING OVER THE ANCHORAGE
BOWL AND MATANUSKA VALLEY. BY TOMORROW MORNING...THE WEATHER
THROUGHOUT THE AREA WILL BEGIN TO CLEAR OUT AS THE UPPER LEVEL LOW
MOVES TOWARDS THE BERING STRAIT AND WEAK HIGH PRESSURE
BUILDS...BRING CLEARING SKIES AND MUCH LIGHTER WINDS TO THE AREA
THAT LOOKS TO LAST INTO MID WEEK.

&&

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

A SURFACE LOW SLOWLY MOVES ACROSS THE ALASKA PENINSULA THIS
EVENING AND INTO THE EASTERN BERING OVERNIGHT. THIS LOW HAS AN
OCCLUDED FRONT EXTENDING FROM THE CENTRAL BERING NEAR THE
PRIBILOFS TO THE KUSKOKWIM VALLEY. SNOW WILL CONTINUE TO DEVELOP
ALONG THIS FRONT WITH A MIX OF RAIN AND SNOW SOUTH OF THE
BOUNDARY. THE FREEZING RAIN ADVISORY REMAINS IN EFFECT ACROSS THE
KUSKOKWIM DELTA AND IS SHOULD EXPIRE BY MIDNIGHT AS COLDER AIR
FILTERS IN ALONG NORTHEASTERLY FLOW. ISOLATED CHANCES FOR FREEZING
RAIN CONTINUES THROUGH TUESDAY ACROSS MUCH OF THE SOUTHWEST AS
WARMER AIR FROM THE PACIFIC MIXES WITH A COLDER AIR MASS INLAND.
GUSTY WINDS INCREASE ACROSS CHANNELED TERRAIN ACROSS THE ALASKA
PENINSULA THIS EVENING WITH PRESSURE GRADIENT TIGHTENING AHEAD OF
THE APPROACHING SURFACE LOW. WINDS SHOULD TAPER DOWN ON MONDAY AS
THE LOW WEAKENS THROUGH THE DAY.

&&

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

NORTHERLY FLOW CONTINUES TONIGHT BRINGING WRAP AROUND MOISTURE ON
THE BACKSIDE OF THE LOW MOVING TO INTO THE EASTERN BERING. MAINLY
SNOW IS EXPECTED FROM THE PRIBILOFS AND NORTH WITH THE SOUTHERN
BERING STAYING IN A MIXED SNOW AND RAIN PATTERN AS TEMPERATURES
MODERATE TOWARD THE ALEUTIANS. PRECIPITATION DIMINISHES LATER ON
TUESDAY AS THE BERING LOW WEAKENS. ANOTHER NORTH PACIFIC STORM
SYSTEM IS DEVELOPING SOUTH OF THE WESTERN ALEUTIANS AND MOVES
NORTH TOWARD THE EASTERN ALEUTIANS BY LATE WEDNESDAY. THIS SYSTEM
WILL BRING ANOTHER ROUND OF MIXED PRECIPITATION AS WARMER
SUBTROPICAL AIR STREAMS NORTH.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
FORECAST THINKING REMAINS LARGELY UNCHANGED FROM LATER THIS WEEK
INTO THE EARLY PART OF NEXT WEEK AS A BROAD UPPER LEVEL RIDGE OVER
THE WEST COAST OF NORTH AMERICA KEEPS WARM AND MOIST SOUTHERLY
FLOW FOCUSED OVER MAINLAND ALASKA. THIS WILL RESULT IN ABOVE
NORMAL TEMPERATURES AND WIDESPREAD PRECIPITATION AS A SERIES OF
DISTURBANCES TRACK NORTHWARD THROUGH THE GULF. PRECIPITATION WILL
BE MOST PREVALENT ALONG THE GULF COAST AND MORE SPORADIC AND
SHOWERY IN NATURE OVER INLAND LOCATIONS DUE TO DOWNSLOPE FLOW ON
THE LEE SIDE OF THE CHUGACH RANGE. MEANWHILE...BROAD CYCLONIC FLOW
WILL MAINTAIN A SHOWERY REGIME OVER THE BERING SEA...WITH THE BULK
OF THE ACTIVITY FOCUSED ALONG THE ALASKA PENINSULA AND EASTERN
ALEUTIANS AS A BROAD NORTH PACIFIC LOW APPROACHES THE AREA THIS
WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FREEZING RAIN ADVISORY 155.
MARINE...STORM 119. GALE WARNING...GALE 125 130 150 155 160 165
172 180.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...CB