Heavy Freezing Spray Warning 2, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SAT JAN 11 2014

.ANALYSIS AND UPPER LEVELS...
A FLAT RIDGE EXISTS OVER THE NE PACIFIC JUST SOUTH OF THE GULF WITH
LONGWAVE TROUGHING IN THE NW PACIFIC AND THE FAR WESTERN BERING/CHAIN
ANCHORED BY A COLD UPPER-LOW NEAR SAKHALIN ISLAND. A 965 MB LOW 150
MILES NORTH OF ATKA IS SLOWLY DRIFTING EAST AND FILLING. WIDESPREAD
GALE FORCE WINDS EXIST AROUND THE NORTHERN AND SOUTHERN QUADRANTS OF
THIS LOW. AN UPPER-LOW NEAR THE CENTRAL ALCAN BORDER IS EJECTING INTO
NW CANADA. THE SOUTHERN MAINLAND NESTLED IN BETWEEN THESE FEATURES
REMAINS IN A NEUTRAL FLOW ALOFT...THOUGH RESIDUAL LOW-LVL MOISTURE IN
THE STAGNANT FLOW HAS ALLOWED LOW CLOUDS AND FOG TO PERSIST ACROSS
UPPER-COOK INLET. A FRONT IS ELONGATING OVER THE EASTERN BERING TO
SOUTHWESTERN GULF (THOUGH IT STRETCHES BACK AND STALLS IN THE N
PACIFIC)...WITH SNOW/RAIN HAVING OVERSPREAD KODIAK ISLAND AND NOSING
INTO BRISTOL BAY. A TRIPLE POINT HAVING FORMED ALONG THE FRONT OVER
THE ISLAND IS TRACKING QUICKLY NORTHEASTWARD. PRECIPITATION
ASSOCIATED WITH THE LOW IN THE BERING IS RATHER SHOWERY. MILD
TEMPERATURES ALLOWS MUCH OF IT TO FALL AS RAIN SHOWERS...THOUGH SOME
COOLER AIR WRAPPING IN BEHIND THE LOW SUPPORTS A MIX OF RAIN AND SNOW
SHOWERS FOR WESTERN PORTIONS OF THE ALEUTIAN CHAIN. ALSO OF NOTE IS
AN UPPER-LOW AROUND 500 MILES SOUTHWEST OF ATTU MOVING EAST.

.MODEL DISCUSSION...
MODELS ARE CLOSE IN SPIRIT WITH THE SHIFTING OF THE PATTERN ALOFT IN
THE COMING DAYS. OUT WEST...THE LOW NORTH OF ATKA IS DEPICTED
DRIFTING TO AROUND 150 MILES SOUTHEAST OF SAINT PAUL SUN EVENING AND
THEN TRACKING ASHORE THE KUSKOKWIM DELTA NEAR KIPNUK MON EVENING.
THERE IS GOOD AGREEMENT WITH THIS DEVELOPMENT AMONG THE MODELS SAVE
FOR THE GFS WHICH IS ABOUT 12 TO 18 HOURS FASTER WITH THE SPEED THAN
THE CONSENSUS. FURTHER EAST...THE TRIPLE-POINT LOW OVER KODIAK IS
SHOWN QUICKLY MOVING TO AROUND 80 MILES EAST OF CAPE SUCKLING SUN
AFTERNOON THEN MOVING ASHORE NEAR YAKUTAT SUN NIGHT. AS THESE
FEATURES RUN THEIR COURSE...THE PATTERN ALOFT SHOWS AMPLIFICATION.
THE UPPER-LOW SOUTHWEST OF ATTU CONTINUES TO DIG THE LONGWAVE
EASTWARD SUN NIGHT THROUGH MON...WITH A REINFORCING SHOT OF ENERGY
SPLITTING OFF FROM THE SAKHALIN ISLAND UPPER-LOW ADDING MORE TO THE
MIX BY MID NEXT WEEK. ALL OF THIS ENERGY WILL BEGIN INTERACTING WITH
THE OLD FRONTAL ZONE IN THE N PACIFIC...WITH A SURFACE LOW DEPICTED
BY THE MODELS FORMING NEAR 40N 164W SUN NIGHT AND MOVING TO AROUND
250 MILES SOUTH OF KODIAK CITY MON AFTERNOON. THE ECMWF AND NAM ARE
SIMILAR WITH TRACK AND SPEED MOVING THE SYSTEM TO NEAR SE PRINCE
WILLIAM SOUND ON TUE. THE GFS LAGS BEHIND BY ABOUT 12 HOURS...WHILE
THE GEM IS SEVERAL HOURS FASTER AND FURTHER EAST WITH THE DEPICTION.
IN GENERAL HAVE NUDGED FORECASTS TOWARDS THE NAM/ECMWF AS THEY HAVE
REASONABLE CONSENSUS AND SOME CONSISTENCY.

.SHORT TERM FORECAST...
SOUTHCENTRAL/GULF...
THE TRIPLE-POINT OVER KODIAK QUICKLY MOVES THROUGH THE GULF
TONIGHT...WITH PERIPHERAL SNOWS EXPECTED TO CLIP THE SOUTHERN KENAI
PENINSULA AND EASTERN PRINCE WILLIAM SOUND...BUT WITH THE FEATURE
BEING FAST MOVING...NOT EXPECTING SIGNIFICANT ACCUMULATIONS. SOME
DOWN INLET FLOW DEVELOPS ACROSS UPPER-COOK INLET AS THE LOW MOVES
THROUGH THE GULF...BUT IT MAY NOT BE ROBUST ENOUGH TO COMPLETELY
SCOUR OUT THE LOW CLOUDS AND FOG TONIGHT. IN THE WAKE OF THE
TRIPLE-POINT AND AMPLIFYING PATTERN ALOFT...A SERIES OF WEAK
SHORTWAVES WILL APPROACH THE REGION FROM THE SOUTH. THESE FEATURES
MAY BE ENOUGH TO SQUEEZE OUT SOME PERIODS OF LIGHT SNOW SUNDAY NIGHT
AND MON. THESE FEATURES APPEAR FAIRLY WEAK...SO HAVE ADVERTISED
CHANCE POPS BUT IF THINGS TREND TOWARDS THE 18Z NAM (WHICH IS HEAVIER
WITH QPF) SUN NIGHT...WILL NEED TO REVISIT FORECASTS TO INCLUDE SOME
ACCUMULATIONS FOR THE POPULATION CENTERS OF UPPER COOK INLET. BY MON
EVENING...PERIPHERAL SNOW/RAIN WITH STRONG WINDS WILL BE PUSHING
TOWARDS KODIAK ISLAND ASSOCIATED WITH THE NEXT PACIFIC SYSTEM.

SOUTHWEST/AKPEN...
LIGHT SNOW FOR BRISTOL BAY ASSOCIATED WITH THE ELONGATING FRONT
TONIGHT TO SUN MORNING. A REINFORCING SHOT OF MOISTURE TO OVERSPREAD
THE SW MAINLAND BY SUN NIGHT AS THE PARENT LOW IN THE BERING SNEAKS
BY THE PRIBILOFS AND TOWARDS THE KUSKOKWIM DELTA COAST. THERE MAY BE
SOME LOCAL AREAS OF BLOWING SNOW THROUGH THE KUSKOKWIM DELTA AS THE
SNOW SHOULD BE RATHER LIGHTWEIGHT AND EASY TO BLOW AROUND IN 25 MPH
WINDS. BLOWING SNOW INTENSITY AND REDUCED VISIBILITY IS NOT EXPECTED
TO BE SUFFICIENT FOR ANY ADVISORIES/WARNINGS. WESTERN REACHES OF
BRISTOL BAY'S AKPEN OUT THROUGH COLD BAY ARE WEAKER SIDE OF THE
FRONT...WHERE TEMPERATURES ABOVE FREEZING WILL ALLOW PRECIP TO FALL
AS MAINLY PASSING RAIN SHOWERS. THE S TO W GALES IN THE CENTRAL CHAIN
MIGRATE TO THE AKPEN AND ADJACENT COASTAL WATERS LATE TONIGHT BEFORE
DIMINISHING TO SMALL CRAFT LEVELS OR LESS SUN NIGHT AS THE PARENT LOW
FILLS AND THE PRESSURE GRADIENT RELAXES.

BERING SEA/ALEUTIANS...
RUN OF THE MILL SNOW AND RAIN SHOWERS WITH THE SLOW MOVING LOW TO
PERSIST ACROSS MUCH OF THE CHAIN. TEMPERATURES ALOFT REMAIN FAIRLY
STEADY STATE...SO COVERAGE AND INTENSITY OF SHOWERS LIKELY TO REMAIN
UNCHANGED THROUGH MON.

.LONG TERM FORECAST...
LATE MONDAY INTO TUESDAY...WHILE THERE IS STILL QUITE A LARGE SPREAD
IN THE TRACK OF THE LOW MOVING INTO THE GULF...THE GLOBAL GUIDANCE
HAS TRENDED TOWARD A MUCH STRONGER LOW TRACKING FARTHER WEST THAN
INITIALLY EXPECTED. SNOW WILL LIKELY OVERSPREAD THE COAST AND COPPER
RIVER BASIN LATE MONDAY INTO EARLY TUESDAY AS THIS LOW TRACKS
INLAND...WITH A POSSIBLE BRIEF CHANGE TO RAIN ALONG THE COAST. INLAND
LOCATIONS FROM COOK INLET INTO THE SUSITNA VALLEY WILL BE QUITE
SENSITIVE TO THE TRACK OF THE LOW WITH RESPECT TO POTENTIAL SNOW
ACCUMULATIONS. SUCH DETAILS WILL BE MORE CLEAR IN THE NEXT COUPLE
DAYS.

THEREAFTER...A MAJOR SHIFT IN THE PACIFIC PATTERN WILL BEGIN AS A
POWERFUL 220 KNOT EAST ASIAN JET STREAM TRACKS EASTWARD INTO THE
NORTHEAST PACIFIC. THERE REMAINS GOOD CONTINUITY AMONG THE GLOBAL
GUIDANCE WITH RESPECT TO A LEADING WARM FRONT SPREADING INTO SOUTHERN
ALASKA SOMETIME ON WEDNESDAY. GIVEN THE COLD DOME IN PLACE...
PRECIPITATION WILL LIKELY BEGIN AS OVERRUNNING SNOW...WITH A
CHANGEOVER TO RAIN ALONG THE COAST. LATE WEEK THROUGH THE WEEKEND...
A DEEP NEGATIVE TILT TROUGH WILL THEN TAKE SHAPE OVER THE NORTHEAST
PACIFIC...WITH A WAVE TRAIN OF STRONG LOWS AND FRONTS TRACKING INTO
SOUTHERN ALASKA AND THE EASTERN BERING SEA. THE ENTIRE SUITE OF
GLOBAL GUIDANCE INCLUDING THE CANADIAN GLOBAL DETERMINISTIC
PREDICTION SYSTEM...GFS...ECMWF...AND THEIR RESPECTIVE ENSEMBLES
DEPICT SIMILAR PATTERNS. SUCH A PATTERN WILL POTENTIALLY HAVE LOCALLY
SIGNIFICANT IMPACTS AS THE ACTIVE PATTERN CONTINUES THROUGH NEXT
WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...132 150 155 165 170 171 172 173 174 175 176 177 185
                351 352 411 412
         HEAVY FREEZING SPRAY...180 181 185 412 414
FIRE WEATHER...NONE

ANALYSIS/MODEL DISCUSSION/SHORT TERM FORECAST...MALOY
LONG TERM FORECAST...AHSENMACHER