Small Craft Advisory 914, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
459 PM AKST SUN NOV 16 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN HAS A LONGWAVE RIDGE THAT EXTENDS UP THE
COAST OF NORTH AMERICA THROUGH THE YUKON AND THEN CURVES OVER THE
ALASKA ARCTIC COAST. A LARGE UPPER LEVEL LOW IS SITUATED NEAR ATTU
WITH A STRONG 250 MB JET RUNNING SOUTH OF THE ALEUTIAN ISLANDS
AND REMAINING SOUTH OF THE FORECAST AREA. THIS PATTERN IS BRINGING
SOUTH TO SOUTHEAST UPPER LEVEL FLOW OVER THE ENTIRE FORECAST AREA.

AT THE SURFACE THERE IS HIGH PRESSURE OVER CANADA THAT STRETCHES
THROUGH THE YUKON AND INTO NORTHERN ALASKA. A LOW IN THE GULF OF
ALASKA IS MOVING NORTHWEST OVER THE SOUTHERN KENAI PENINSULA. THIS
IS CREATING STRONG WINDS ALONG THE NORTH GULF COAST IN BETWEEN
THIS LOW AND THE HIGH IN THE NORTHERN PART OF THE STATE. THIS
TIGHT GRADIENT IS CAUSING DOWNSLOPING OVER MUCH OF SOUTH CENTRAL
ALASKA TODAY.

&&

.MODEL DISCUSSION...
MODELS ARE HANDLING THE LOW EAST OF KODIAK WELL AND ARE IN GOOD
AGREEMENT WITH THE WAY IT TRACKS NORTHWEST AND THEN DISSIPATES
LATE TONIGHT. MODEL SPREAD GROWS TUESDAY AS ANOTHER LOW MOVES UP
FROM THE NORTHEAST PACIFIC AND TRACKS TOWARD KODIAK
ISLAND...WHICH IS MOST PROBLEMATIC FOR THE WIND FORECAST OVER THE
WESTERN GULF AND KODIAK ISLAND. THE GFS BRINGS THE LOW TO THE
SOUTH SIDE OF KODIAK ISLAND TUESDAY AFTERNOON WHILE THE NAM AND
ECMWF RUN IT NEAR THE BARREN ISLANDS AT THAT TIME. THE GEM MODEL
HAS THE MORE NORTHERN TRACK BUT BRINGS IT ALL THE WAY TO NEAR
ILIAMNA BY TUESDAY AFTERNOON. IT MAY TAKE A FEW MODEL RUNS TO GAIN
CONFIDENCE IN THE TRACK OF THIS LOW.

THE BROAD AND COMPLEX AREA OF LOW PRESSURE OVER THE MAJORITY
OF THE BERING SEA CURRENTLY HAS THREE SEPARATE CENTERS AND MODELS
ARE ALL DOING WELL RESOLVING ALL THREE. THE ONE SOUTH OF THE
CENTRAL ALEUTIANS WILL STRENGTHEN TONIGHT AND MOVE TOWARD DUTCH
HARBOR AND THEN ALL MODELS DEPICT IT CURVING BACK TO THE
NORTHWEST AS IS COMMON IN COMPLEX LOWS SUCH AS THIS. THE ONLY
MODEL THAT GETS A LITTLE OFF WITH THIS LOW IS THE GFS WHICH IS
PUSHING THE LOW CENTER 200 PLUS MILES FARTHER WEST THAN ANY OF
THE OTHER MODELS BY TUESDAY NIGHT.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE FOCUS OF THE FORECAST FOR TONIGHT AND EARLY TOMORROW WILL
REVOLVE AROUND THE CHANCES FOR FREEZING RAIN AROUND PARTS OF THE
SOUTHCENTRAL. A LOW PRESSURE SYSTEM AND ATTENDANT FRONT ARE MOVING
ONSHORE THE KENAI PENINSULA WHICH WILL SPREAD AREAS OF RAIN OVER
KACHEMAK BAY AND THE KENAI PENINSULA. THE REMAINDER OF THE WESTERN
KENAI WILL REMAIN MOSTLY DRY DUE TO DOWNSLOPE FLOW...THOUGH SOME
SPRINKLES MAY REACH THE GROUND AS CROSS BARRIER FLOW BEGINS TO
WEAKEN THIS EVENING. FURTHER TO THE NORTH...ANCHORAGE AND THE
MATANUSKA VALLEY ARE UNDER THE SAME REGIME. A TROUGH PASSAGE LATER
THIS EVENING MAY MOISTEN THE COLUMN ENOUGH FOR SOME PRECIPITATION
TO REACH THE GROUND...HOWEVER PRECIPITATION TYPE IS GOING TO BE
TRICKY. THE 00Z/17 SOUNDING FROM ANCHORAGE INDICATES A FREEZING
RAIN THERMAL PROFILE WITH 925 MB TEMPERATURES AROUND +3C. THE WET
BULB TEMPERATURE REMAINS BELOW ZERO THROUGHOUT THE COLUMN WHICH
WOULD SIGNIFY SNOW BUT DOWNSLOPE DRYING SHOULD PRECLUDE THAT FROM
HAPPENING. EXPECT SOME SPRINKLES OR VERY LIGHT RAIN/FREEZING RAIN
AROUND ANCHORAGE AND THE MATANUSKA VALLEY TONIGHT TAPERING OFF
TOMORROW MORNING.

A BETTER CHANCE FOR FREEZING RAIN EXISTS IN THE SUSITNA VALLEY.
STEADY LIGHT FREEZING RAIN WILL DEVELOP IN THE LATE EVENING AND
CONTINUE OVERNIGHT...FIRST AROUND WILLOW/HOUSTON THEN SPREADING
NORTHWARD. NORTH OF TALKEETNA SHOULD REMAIN COLD ENOUGH FOR SNOW.

OVERNIGHT MONDAY INTO TUESDAY ANOTHER LOW/FRONT WILL MOVE INTO THE
GULF AND BRING A SIMILAR LOOKING SYSTEM TO THE AREA.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A CONTINUED AND PERSISTENT SOUTHEAST FLOW ALOFT WILL REMAIN
OVER SOUTHWEST ALASKA THROUGH MID WEEK. WIDE SPREAD SHOWERY
CONDITIONS WILL CONTINUE TO EFFECT MUCH OF THE SOUTHWEST
MAINLAND...AS MULTIPLE WEAK DISTURBANCES TRAVERSE THE AREA
THROUGH MONDAY EVENING. RAIN WILL BE THE DOMINANT PRECIPITATION
TYPE THROUGH MUCH OF THE MAINLAND...WITH POCKETS OF FREEZING RAIN
POSSIBLE ACROSS THE LOWER KUSKOKWIM VALLEY WHERE SURFACE
TEMPERATURES REMAIN BELOW FREEZING. A MORE VIGOROUS FRONT WILL
SPREAD INTO THE REGION MONDAY NIGHT...SPREADING WIDESPREAD
PRECIPITATION ACROSS THE REGION THROUGH MID WEEK.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
SCATTERED SHOWERS WILL GIVE WAY TO WIDESPREAD RAIN AND RAIN
SHOWERS AS A STRENGTHENING NORTH PACIFIC LOW MOVES INTO THE
BERING LATE TONIGHT THROUGH WEDNESDAY. THE STRONGEST WINDS WILL
DEVELOP ACROSS THE EASTERN ALEUTIANS AND PRIBILOF ISLANDS
TOMORROW...AS WELL AS ACROSS THE CENTRAL ALEUTIANS WEST OF DUTCH
HARBOR AS NORTHWEST WINDS INCREASE BEHIND THE LOW. THE LOW WILL
SLOWLY WEAKEN THROUGH WEDNESDAY...AS IT SLOWLY DRIFTS INTO THE
CENTRAL BERING.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE BLOCKING PATTERN LOOKS TO CONTINUE THROUGH MUCH OF NEXT WEEK
WITH A PERSISTENT RIDGE OVER WESTERN CANADA AND A BROAD UPPER
LEVEL TROUGH OVER THE ALEUTIANS AND BERING SEA. THIS WILL RESULT
IN A CONTINUATION OF SOUTHERLY FLOW OVER THE GULF OF ALASKA AND
HELP TO KEEP THE BULK OF THE PRECIPITATION FOCUSED ALONG THE
NORTH GULF COAST INTO NEXT WEEKEND...WITH OCCASIONAL CHANCES FOR
PRECIPITATION FURTHER INLAND AS OCCASIONAL DISTURBANCES ROTATE
THROUGH THE GULF. TEMPERATURES WILL REMAIN SLIGHTLY ABOVE NORMAL
AND ALLOW MOST OF THE PRECIP TO FALL AS RAIN...WITH SNOW MIXING IN
AT TIMES. MEANWHILE...THE BERING SEA WILL REMAIN IN A SHOWERY
REGIME WITH AN ELONGATED UPPER LOW CENTERED OVER THE ALEUTIAN
CHAIN AND VARIOUS WAVES ROTATING THROUGH THE EASTERN BERING. THE
STRONGEST OF THESE FEATURES LOOKS TO APPROACH THE AKPEN LATE IN
THE WEEK AS A NORTH PACIFIC SHORT WAVE ROUNDS THE BASE OF THE
TROUGH AND AN ASSOCIATED SURFACE LOW RAPIDLY DEEPENS BENEATH THE
LEFT EXIT REGION OF A 160 KT JET STREAK. THE DETAILS OF THIS
SYSTEM WILL COME INTO BETTER FOCUS LATER IN THE WEEK...BUT THE
MAIN IMPACTS WILL LIKELY BE WIDESPREAD RAIN AND GUSTY SOUTHEAST
WINDS OVER THE EASTERN BERING.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 125 130 131 139 155 165 170 172
                        174 176 177 179 180 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...MTL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP
LONG TERM...CB