Small Craft Advisory 960, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM ADT THU OCT 19 2006

.DISCUSSION...

ANALYSIS...A LARGE AREA OF CYCLONIC CIRCULATION DOMINATES THE BERING
SEA. A MATURE OCCLUDED 986 MB SURFACE LOW SITS NORTHWEST OF THE
PRIBILOFS WITH A WEAKENING FRONT EXTENDING FROM THE LOW CENTER ACROSS
THE NORTHERN BERING AND SOUTHEASTWARD ACROSS SOUTHWEST ALASKA. COLD
AIR ADVECTION ALOFT COMBINED WITH THE WARM BERING SEA WATERS HAS
PRODUCED A MODERATELY UNSTABLE ATMOSPHERE (AS CONFIRMED BY THE 12 UTC
COLD BAY SOUNDING) AND WIDESPREAD SHOWERS....SOME LIKELY CONTAINING
MODERATE TO HEAVY RAIN AS WELL AS GUSTY WINDS. THERE IS A VERY TIGHT
SURFACE PRESSURE GRADIENT BETWEEN THE 986 MB LOW AND A 1031 HIGH
CENTERED DOWN AROUND 40N 174E. GALE FORCE WINDS EXTEND ACROSS THE
SOUTHERN BERING/CENTRAL AND EASTERN ALEUTIANS/AND AKPEN WITH
OCCASIONAL STORMS OVER THE SOUTHERN BERING. SHIP REPORTS ALONG THE
SOUTHERN AKPEN INDICATE GUSTS OF 60 TO 70 KT THROUGH CHANNELED
AREAS. THE LONG WESTERLY FETCH ACROSS THE SOUTHERN BERING HAS BUILT
SEAS UP TO AROUND 20 FEET. AN UPPER SHORT-WAVE IS EMBEDDED IN THE
WESTERLY FLOW OVER THE WESTERN ALEUTIANS AND WILL PLAY A ROLE IN
AMPLIFICATION OF THE CURRENT PATTERN. A SHORT-WAVE RIDGE SITS OVER
SOUTHCENTRAL THIS MORNING WITH LOTS OF LOW CLOUDS AND SOME AREAS OF
DRIZZLE AND FOG. CONDITIONS ACROSS THE REGION HAVE BEEN SLOWLY
IMPROVING THROUGH THE MORNING HOURS...BUT MOISTURE ASSOCIATED WITH
FRONT OVER SOUTHWEST ALASKA IS ON THE WAY. FINALLY...AN ELONGATED
LOW IS NEARLY STATIONARY AT AROUND 35N 159W WITH MOISTURE EXTENDING
WELL NORTH OF THE LOW.

MODEL ANALYSIS...FAIR INITIALIZATION BY ALL MODELS WITH REGARD TO
SYNOPTIC FEATURES. NAM CONTINUES TO BE A STEP OFF FROM THE GFS/UKMET
WITH THE SPEED OF THE LOWS IN THE SHORT-TERM. GFS SHOWS FAIR
RUN-TO-RUN CONSISTENCY. LOW TRACKING INTO GULF IS 9 MB DEEPER THAN
THE LAST RUN WHICH IS DEEPER THAN THE OTHER MODELS. WITH COLD AIR
FEEDING INTO THE SYSTEM...AN AMPLIFYING TROUGH...AND SOME UPPER JET
SUPPORT...AGREE WITH A DEEPER SOLUTION...BUT NOT READY TO MAKE THAT
BIG OF A JUMP. WILL TREND SIGNIFICANTLY TOWARD THE STRONGER SOLUTION.

OUT WEST ALSO PREFER GFS WHICH SHOWS VERY GOOD RUN-TO-RUN CONSISTENCY
WITH NEXT LOW MOVING INTO SOUTHERN BERING.

SOUTHCENTRAL FORECAST...SHORT-WAVE RIDGE WILL SLIDE INTO CANADA THIS
EVENING AND FLOW WILL BECOME CYCLONIC WITH COLD ADVECTION SHOWERS
OVERSPREADING THE REGION TONIGHT. FREEZING LEVELS WILL DROP TO
AROUND 2000 TO 2500 FEET BY FRIDAY MORNING RESULTING IN SOME SNOW
SHOWERS AT HIGHER ELEVATIONS. DO NOT EXPECT ANY SIGNIFICANT SNOW
ACCUMULATION. SHORT-WAVE MOVING ACROSS WESTERN ALEUTIANS WILL HELP
AMPLIFY UPPER TROUGH AND PICK UP PACIFIC LOW. WITH COLD AIR FEEDING
INTO SYSTEM IT WILL DEEPEN AS IT TRACKS TO PRINCE WILLIAMS SOUND
SATURDAY. THERE WILL BE A BRIEF BREAK IN THE PRECIP FOR MOST AREAS
FRIDAY AFTERNOON INTO EVENING AS RIDGING OCCURS AHEAD OF LOW...BUT
MOISTURE WILL OVERSPREAD SOUTHCENTRAL LATE FRIDAY NIGHT AND SATURDAY.
AT THIS POINT WILL FORECAST GALES FOR GULF COASTAL WATERS...BUT THERE
IS POTENTIAL FOR STORMS. COLD AIR ON THE BACK SIDE OF LOW WILL CREATE
POTENTIAL FOR THE FIRST SNOWFALL FOR LOWER ELEVATIONS ALONG THE COOK
INLET CORRIDOR (INCLUDING ANCHORAGE) SATURDAY NIGHT. STILL NEED TO
GET A BETTER HANDLE ON LOW TRACK AND DEPTH BEFORE DECIDING IF THIS
WILL OCCUR.

BERING SEA/ALEUTIANS/SOUTHWEST ALASKA FORECAST...AS LOW CENTER MOVES
NORTHWARD THIS EVENING SHORT-WAVE WILL ROTATE SOUTHWARD ACROSS
CENTRAL BERING TOWARD PRIBILOFS ISLAND FRIDAY MORNING BEFORE LIFTING
NORTHWARD FRIDAY AFTERNOON. THIS WILL MAINTAIN GUSTY WINDS AND
MODERATE TO HEAVY PRECIP OVER THIS REGION THROUGH FRIDAY MORNING.
LONG WESTERLY FETCH WILL PRODUCE SLIGHTLY HIGHER THAN NORMAL TIDES
OVER PORTIONS OF THE KUSKOKWIM COAST. A HIGH SURF ADVISORY HAS BEEN
ISSUED TO ADVISE OF THIS. AIR ALOFT IS COLD ENOUGH THAT RAIN MAY MIX
WITH FROZEN PRECIP AT TIMES. AS WINDS AND SHOWERS DIMINISH LATE
FRIDAY THE NEXT SYSTEM WILL MOVE TO THE WESTERN ALEUTIANS AND THEN
TRACK EASTWARD ACROSS THE SOUTHERN BERING SATURDAY BRINGING MORE
RAIN AND WIND. NEAR ZONAL JET MEANS LOW WILL MOVE ALONG QUICKLY AND
OTHERS WILL BE ON ITS TAIL.

EXTENDED FORECAST...THERE APPEARS TO BE A CHANGE IN PATTERN AS WE
HEAD INTO THE EXTENDED PERIOD. RIDGE ALONG WEST COAST OF U.S. AND
CANADA IS BROKEN DOWN...AT LEAST FOR SEVERAL DAYS. A NEAR ZONAL JET
MAINTAINS AN ACTIVE FAST-MOVING STORM PATTERN. THIS ALSO ALLOWS
COLDER AIR TO WORKS IT WAY EASTWARD INTO SOUTHCENTRAL MEANING A
BETTER CHANCE FOR PRECIPITATION TO FALL AS SNOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH SURF ADVISORY ZONE 155.
MARINE...GALES 120 130 132 160 170 171 172 175 176 179 AND 180.

SEB OCT 06