Small Craft Advisory 102, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SAT FEB 1 2014

.ANALYSIS AND UPPER LEVELS...
AN UPPER-LVL RIDGE IS PREDOMINANT OVER THE SOUTHERN MAINLAND AND
GULF...WITH AN UPPER-HIGH CENTER PINCHING OFF NEAR THE UPPER
KUSKOKWIM VALLEY. ANOTHER UPPER-LVL RIDGE BUILDS NORTHEASTWARD
THROUGH THE CENTRAL BERING SEA. IN BETWEEN THESE RIDGES AN UPPER LOW
IS CUTTING OFF NEAR COLD BAY AND IS NEARLY STATIONARY. AN OLD TROUGH
AXIS IS BEING SHEARED BETWEEN THE CUT OFF LOW AND GULF RIDGE TO THE
EAST...WITH THE CLOUD SHIELD BRUSHING KODIAK ISLAND BRISTOL BAY. AT
THE SURFACE...THERE IS A WEAK LOW OVER THE KUSKOKWIM DELTA NEAR
BETHEL THAT IS FILLING...WITH SOME RESIDUAL LIGHT SNOW ENDING OVER
THIS REGION. ACROSS SOUTHCENTRAL...MODEST NORTH TO WEST GAP WINDS
PERSIST ASSOCIATED WITH A TROUGH OF LOW PRESSURE ALONG THE NORTH GULF
COAST...THOUGH THIS FEATURE IS WEAKENING A BIT. ACROSS UPPER COOK
INLET...SUBSIDENCE FROM THE UPPER RIDGE SUPPORTS SOME AREAS OF
FOG...OTHERWISE AREAS ARE PRECIPITATION FREE AND FAIRLY BENIGN
SENSIBLE WEATHER WISE. FURTHER WEST...A NEAR STATIONARY FRONTAL
BOUNDARY IS DRAPED FROM NORTH TO SOUTH NEAR 180 LONGITUDE OVER THE
WESTERN CHAIN AND BERING. A SURFACE WAVE ALONG IT'S AXIS NEAR SHEMYA
IS QUICKLY TRACKING NORTHWARD. ALSO OF NOTE IS A PACIFIC LOW AROUND
1300 MILES SOUTH OF ATKA DRIFTING NORTHEAST.

.MODEL DISCUSSION...
MODELS SHOW THE UPPER-RIDGING IN THE BERING POKING NORTHEASTWARD AND
MERGING/CONSOLIDATING WITH THE UPPER-HIGH CURRENTLY CENTERED OVER THE
UPPER KUSKOKWIM VALLEY...WITH A NEW UPPER-HIGH CENTER BECOMING
ESTABLISHED OVER THE NORTH SLOPE OF AK BY MON. NEAR NEUTRAL FLOW
ALOFT OVER THE SOUTHERN MAINLAND IS DEPICTED BECOMING SLIGHTLY
EASTERLY UNDERNEATH THE UPPER HIGH. THE CUT OFF LOW MEANDERS IN THE
VICINITY OF THE SHUMAGIN ISLANDS THROUGH LATE SUN NIGHT WHILE
CONTINUING TO FILL AND SHEAR OUT. MODELS THEN SHOW IT WILL PINWHEEL
NW INTO THE EASTERN BERING...WHERE IT MAY INTERACT WITH ENERGY
ROUNDING THE UPPER HIGH THAT IS TO THE NORTHEAST. THIS NOISY PATTERN
RESULTS IN SOME ORIENTATION AND TIMING DIFFERENCES AMONG THE MODELS
AS ALL THIS PLAYS OUT...BUT IN GENERAL...THIS RESIDUAL UPPER-LOW
ENERGY DRIFTS NORTHWEST AND LARGELY AWAY FROM THE AOR BY TUE.

THE PACIFIC LOW WELL SOUTH OF ATKA MOVES TO AROUND 500 MILES SOUTH OF
UNALASKA MON AFTERNOON...THEN DRIFTS TO AROUND 600 MILES SOUTHWEST OF
UNALASKA TUE AFTERNOON. MODELS SUGGEST THAT PROGRESS FURTHER NORTH OF
THIS LOW IS SHUNTED BY UPPER-LVL RIDGING WHICH REBUILDS IN FORCE OVER
THE GULF AND SOUTHERN MAINLAND IN THE WAKE OF THE DEPARTING
AFOREMENTIONED AKPEN UPPER-LOW. ASSOCIATED QPF WITH AN ASSOCIATED
FRONT HOWEVER IS DEPICTED SNEAKING UP TO THE FAR SW GULF/KODIAK
ISLAND BACK THROUGH THE AKPEN AND EASTERN CHAIN. PENDING THAT
RESIDUAL AKPEN UPPER-LOW POSITION...AN APPRECIABLE CHUNK OF THIS
MOISTURE COULD GET STRETCHED AS FAR NORTH AS NUNIVAK ISLAND BY EARLY
TUE...THE ECMWF BEING MOST GENEROUS WITH THIS LATTER POSSIBILITY.
FORECASTS HAVE NOT GONE THIS AGGRESSIVE AT THIS TIME.

.SHORT TERM FORECAST...
SOUTHCENTRAL/GULF...
ACROSS THE SOUTHERN MAINLAND...FAIRLY CLEAR SKIES OVERNIGHT WILL ONCE
AGAIN ALLOW FOR GOOD RADIATIONAL COOLING AND COUPLED WITH THE LIGHT
WINDS EXPECTED...SHOULD SEE CONDITIONS SUPPORTIVE OF FOG. CAVEAT
APPEARS TO BE LESS SUBSIDENCE FROM THE UPPER-RIDGING...SO PERHAPS FOG
DOES NOT GET QUITE AS DENSE/THICK. ACROSS THE ANCHORAGE BOWL...THE
LONGER THIS AFTERNOON'S FOG HANGS AROUND INTO THE EVENING...THE
LIKELIER IT WILL BECOME DENSE ONCE AGAIN ON ACCOUNT THAT LITTLE OTHER
CHANGE TO THE SYNOPTIC PATTERN IS ANTICIPATED. OVERALL...THE SOUTHERN
MAINLAND LARGELY LOOKS TO REMAIN PRECIPITATION FREE THROUGH MON AS
THE FLOW REMAINS NEUTRAL OR DRY/OFF-SHORE IN NATURE.

FOR THE GULF...THE TROUGH OVER THE NORTHERN GULF COAST WILL DIMINISH
TONIGHT...BUT NORTH TO WEST GAP WINDS MAY NOT DIE OFF COMPLETELY...
ESPECIALLY OVER EASTERN PRINCE WILLIAM SOUND AS RELATIVELY COLD AIR
POOLED UP IN THE COPPER RIVER BASIN CONTINUES TO SQUIRT THROUGH.
ACROSS KODIAK ISLAND...THE UPPER-LOW TO THE WEST WILL GET A SMALL
BOOST IN MOISTURE FROM A WAVE PINWHEELING UP FROM THE SOUTHWEST.
OFF-SHORE FLOW BECOMES MORE ONSHORE IN NATURE AS SUNDAY WEARS
ON...WITH SOME LIGHT PRECIPITATION EXPECTED. TEMPERATURES/THICKNESSES
SUPPORT COLD RAIN...THOUGH SOME WET SNOW IS ALSO POSSIBLE AT LEAST
INITIALLY. THE PRECIP GETS A BIGGER BOOST AS THE LOW IN THE NORTH
PACIFIC PUSHES A FRONT TO THE SOUTHERN GULF ON MON. THERE IS A SMALL
CHANCE THAT SOME OF THIS PERIPHERAL MOISTURE COULD BRUSH THE SW KENAI
PENINSULA AS LIGHT SNOW.

SOUTHWEST/AKPEN...
UPPER-RIDGING BUILDING FROM BOTH THE SOUTHWEST AND SOUTHEAST SHOULD
MANIFEST INTO A GENERAL DRY PATTERN FOR SW AK AS WELL THROUGH MON.
RESIDUAL LOW LVL MOISTURE TRAPPED UNDER INVERSIONS WILL STILL SUPPORT
SOME LOW CLOUDS AND FOG...THOUGH THIS RISK BECOMES TEMPERED AS FLOW
INCREASINGLY BECOMES MORE OFF-SHORE IN NATURE IN RESPONSE TO THE
BUILDING SURFACE HIGH TO THE NORTH AND GENERAL LOW PRESSURE TO THE
SOUTH (N PACIFIC). PASSING SHOWERS FOR THE AKPEN WILL GIVE WAY TO
SOME STEADIER PRECIPITATION SUN AND MON. INITIALLY PRECIPITATION
COULD BE WET SNOW/RAIN MIX BUT THE ADVANCING WARM ADVECTION WITH THE
PACIFIC LOW SHOULD TRANSITION EVERYTHING TO A COLD RAIN. NORTH TO
EAST WINDS 20 KT OR LESS TREND TO GALES AS THE PACIFIC FRONT SQUEEZES
THE PRESSURE GRADIENT MORE BY MON.

BERING SEA/ALEUTIANS...
THE SURFACE WAVE NEAR SHEMYA QUICKLY TRACKS INTO EASTERN SIBERIA ON
SUN WITH RAIN TAPERING TO SHOWERS AND GALE FORCE WINDS ENDING
ABRUPTLY FROM SOUTH TO NORTH. RIDGING THEN BECOMES A DOMINANT FEATURE
IN THE BERING SEA WITH MAINLY PERIPHERAL EFFECTS FROM THE PACIFIC
LOW. MOST OF THE IMPACTS WILL BE OVER THE EASTERN AND CENTRAL CHAIN
WHICH WILL SEE THE ASSOCIATED FRONT PUSH TOWARDS THE REGION WITH SOME
GALES AND SOME RAIN/WET SNOW BY MON.

.LONG TERM FORECAST...
THE BLOCKING PATTERN STILL LOOKS TO DOMINATE MID TO LATE NEXT WEEK.
THIS WILL MEAN DRY AND NEAR NORMAL TEMPERATURES FOR MOST AREAS.
MODELS SHOW SOME AGREEMENT THAT A WEAK UPPER LEVEL TROUGH WILL SNEAK
THROUGH THE INTERIOR OF THE STATE ON WED. IT WILL BE INTERESTING TO
SEE HOW MODELS HANDLE THIS TROUGH AND WHAT KIND OF COLD AIR AND WINDS
IT COULD BRING SOUTH WITH IT. BECAUSE AFTER IT MOVES OFF THE SOUTH
COAST OF THE MAINLAND...THE RIDGE REBUILDS ON THU. BUT THEN
ANOTHER...MUCH STRONGER UPPER LEVEL TROUGH IS EXPECTED TO TAKE A VERY
SIMILAR PATH EARLY FRIDAY. THE OPERATIONAL ECMWF IS THE MOST
AGGRESSIVE WITH THIS FEATURE...BUT THE GFS HAS TRENDED STRONGER AS
WELL. DEPENDING ON THE EXACT ORIENTATION AND THE AMOUNT OF COLD AIR
IT BRINGS WITH IT FROM CANADA...THIS COULD BE A SIGNIFICANT WIND
EVENT FOR MUCH OF SOUTH CENTRAL. AND WITH LITTLE SNOW PACK AND
CONTINUED DRY CONDITIONS...BLOWING DUST WOULD BE A REAL CONCERN. FIRE
WEATHER INTERESTS SHOULD ALSO KEEP AN EYE ON THIS POSSIBLE EVENT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...177 178 185 411 412 413
         HEAVY FREEZING SPRAY...180 181 185
FIRE WEATHER...NONE

ANALYSIS/MODEL DISCUSSION/SHORT TERM FORECAST...JAM
LONG TERM FORECAST...MSO