High Wind in Alaska, October 14, 2012

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
540 AM AKDT SUN OCT 14 2012

.ANALYSIS AND UPPER LEVELS...
A COMPLEX SYSTEM IS DEVELOPING OVER THE GULF THIS MORNING. A SURFACE
LOW OVER KODIAK ISLAND IS DRIFTING SLIGHTLY NORTH AND WEAKENING. THIS
FEATURE IS CONSIDERABLY FURTHER WEST COMPARED TO YESTERDAY'S PROGS
AND HAS ALLOWED A SWATH OF SNOW TO PERSIST OVER EASTERN BRISTOL BAY.
A PACIFIC LOW IS CENTERED AROUND 400 MILES SOUTHEAST OF MIDDLETON
ISLAND AND IS MOVING NORTH THROUGH THE GULF OF AK. ALOFT A VIGOROUS
UPPER-LVL LOW HAS SLIPPED SOUTH OF THE AKPEN AND MOVING EAST TOWARDS
SW FRINGES OF THE GULF OF AK. A SERIES OF WEAK AND UNORGANIZED
DISTURBANCES ROTATING AROUND THE BROAD LOW PRESSURE IN THE GULF ARE
BRUSHING COASTAL AREAS AND PRINCE WILLIAM SOUND WITH SHOWERS. FURTHER
WEST...HIGH PRESSURE IS DOMINANT OVER THE WESTERN CHAIN...WITH A
SQUEEZED PRESSURE GRADIENT CONTINUING TO PRODUCE STRONG NORTH TO
NORTHWEST GALES OVER THE EASTERN BERING/AKPEN...WITH STRONGER GUSTS
THROUGH CHANNELED TERRAIN.

.MODEL DISCUSSION...
MODELS SATISFACTORILY CAPTURE THE MAIN WEATHER FEATURES. AS MENTIONED
PREVIOUSLY...THE LOW NEAR KODIAK WAS NOT HANDLED WELL IN YESTERDAY'S
OVERNIGHT MODELS...BUT THE NAM HAS INITIALIZED IT WELL THIS MORNING.
IN GENERAL TERMS...MODELS SHOW THE ENERGY FROM THE PACIFIC LOW IN THE
SOUTHEASTERN GULF AND THE RESIDUAL LOW NEAR KODIAK PHASING TONIGHT
WITH A NEW SURFACE LOW CENTER EXPECTED TO BE POSITIONED AROUND 120
MILES SOUTHWEST OF MIDDLETON ISLAND MON MORNING. MODELS THEN TRACK
THE LOW UP TOWARDS PRINCE WILLIAM SOUND ON TUE. WITH ALL OF THE
VARIOUS PIECES OF ENERGY INTERACTING...EXACT PLACEMENTS OF THE
SURFACE LOW ARE STILL A BIT UNCERTAIN BUT THERE IS GOOD AGREEMENT
WITH THE SPIRIT OF THIS TREND. TIMING AND SCOPE OF COLD ADVECTION
WRAPPING BEHIND THE COMPLEX LOW IS HANDLED SIMILARLY OVER THE WESTERN
GULF AND LOWER COOK INLET. ACROSS UPPER-COOK INLET AND THE MAT-SU
VALLEYS...THE GFS LAGS BEHIND THE NAM AND ECMWF IN BRINGING COLD AIR
IN. BASED ON REASONABLE INITIALIZATION AND DEGREE OF COLD ADVECTION
ALREADY EXPERIENCED OVER UPSTREAM AREAS OF SOUTHWEST AK AND EASTERN
BERING...FAVOR THE FASTER SOLUTIONS. FORECAST PACKAGE TRENDS TO THE
ECWMF BY MID-WEEK AND THEN TOWARDS HPC GUIDANCE FOR THE LATTER PART
OF THE WEEK.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
THE COMPLEX LOW WILL SWING A FRONT TO THE NORTHERN GULF TONIGHT AND
THUS THE FOCUS OF THE STEADIEST PRECIPITATION WILL CONTINUE ALONG
COASTAL AREAS WITH INTERIOR SECTIONS SEEING MOSTLY CLOUDY SKIES AND
GENERALLY ONLY PASSING SHOWERS. THE MORNING ANCHORAGE SOUNDING
CONFIRMS WARM ADVECTION POKING ACROSS THE CHUGACH AND KENAI
RANGES...SO WOULD EXPECT FALLING PRECIPITATION ACROSS MOST AREAS TO
BE RAIN (THOUGH SOME WET SNOW MIXED IN STILL POSSIBLE) EXCEPT FOR THE
HIGHEST PASSES AND AREAS FURTHER NORTH IN THE COPPER RIVER BASIN AND
INTERIOR SUSITNA VALLEY. COLD ADVECTION BLEEDS EAST OF THE ALEUTIAN
RANGE OVERNIGHT TONIGHT WITH RATHER STRONG NORTHWEST WINDS ADVANCING
THROUGH WESTERN MARINE AREAS...AND SPREADING TO CENTRAL AND EASTERN
GULF AREAS THROUGH TUE. PRECIPITATION LIKELY TO BEGIN MIXING OR
CHANGING TO SNOW ACROSS KODIAK ISLAND AS THIS DEVELOPS. THE NAM
SOLUTION SHOWS 850 MB TEMPERATURES COOLING TO MINUS 6 CELSIUS AND
COOLER BEGINNING MON NIGHT ACROSS UPPER COOK INLET...AND WITH AN
INVERTED TROUGH AXIS DRAPED THROUGH THE AREA SUPPORTING
PRECIPITATION...WOULD EXPECT A TRANSITION SAFELY BACK TO ALL SNOW
FROM WEST TO EAST. PROXIMITY OF THE RESIDUAL LOW NEAR PRINCE WILLIAM
SOUND WILL BE ANOTHER VARIABLE IN TERMS OF DURATION AND SCOPE OF QPF
FIELD MON NIGHT INTO TUE.

SOUTHWEST...
BRISK NORTH WINDS CONTINUE OVER THE SW MAINLAND IN THE SQUEEZED
PRESSURE GRADIENT...WITH MAINLY ONLY SOME INSTABILITY SHOWERS IN
CYCLONIC FLOW ALOFT. THE LION'S SHARE OF STEADY PRECIPITATION IS OVER
BRISTOL BAY...AND FALLING AS SNOW DUE TO A WELL ESTABLISHED COOL
AIRMASS. PRECIPITATION HERE SHOULD EASE AS LIFT WITH THE SUPPORTING
LOW PRESSURE SYSTEM ENDS. BRISK NORTHWEST FLOW IN IT'S WAKE WILL KEEP
WESTERN FACING SLOPES OF THE ALASKA AND ALEUTIAN RANGES UNDER THE GUN
FOR PERSISTENT SNOW SHOWERS HOWEVER. CONDITIONS REMAIN SEASONABLY
COOL INTO MIDWEEK.

BERING SEA/ALEUTIANS...
STRONGEST WINDS CONTINUE OVER THE EASTERN CHAIN BACK THROUGH THE
AKPEN. CONDITIONS WILL BE SLOW TO WEAKEN DUE TO THE SLOW MOVING LOW
IN THE GULF AND STUBBORN HIGH PRESSURE TO THE WEST. MODERATELY HEAVY
SNOW SHOWERS EXPECTED ALONG THE AKPEN...ENHANCED AT TIMES BY
SHORTWAVES DROPPING SOUTH BEHIND THE UPPER-LOW TO THE EAST.

.LONG TERM FORECAST...
THE UPPER-LOW IN THE GULF MOVES TO THE EASTERN GULF LATE THIS
WEEK...WITH UPPER-RIDGING FROM THE BERING SEA EXPANDING EAST TO THE
SOUTHERN MAINLAND. THIS SHOULD HELP DRY CONDITIONS OUT ALBEIT WITH
CONSIDERABLY COOLER TEMPERATURES. GUSTY NORTH TO WEST OUTFLOW WINDS
TO ALSO BE A CONSIDERATION OVER THE NORTHERN GULF AS THE LOW EXITS
EAST. MODELS SHOW A LOW OVER THE KAMCHATKA PENINSULA LATE WEEK
SWINGING A FRONT TO THE WESTERN CHAIN AND BERING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...130 132 138 140 150 155 160 165 170 171 179 180 352
                414
FIRE WEATHER...NONE

MALOY