Flood Watch 1, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
3 PM AST WED JAN 24 2007

.DISCUSSION...

A 955 MB LOW 400 MILES SOUTH OF ATKA WILL CONTINUE TO SLOWLY MOVE
NORTHEAST TONIGHT CROSSING THE ALASKA PENINSULA EARLY FRIDAY
MORNING...MEANWHILE HIGH PRESSURE WILL CONTINUE TO REPLACE A
DEPARTING LOW IN THE EASTERN GULF OF ALASKA. SATELLITE AND MODELS
SHOW AN OCCLUDED FRONT WITH PLENTY OF MOISTURE DRAPED ACROSS THE
CENTRAL ALEUTIANS AND EXTENDING SOUTH OUT IN FRONT OF THE
AFOREMENTIONED LOW. A COLD UPPER LEVEL TROUGH OVER MOST OF MAINLAND
ALASKA WILL GIVE WAY TO A SIGNIFICANT UPPER LEVEL RIDGE BUILDING IN
OVER SOUTHEAST ALASKA THROUGH THURSDAY...USHERING IN A SIZABLE WARMUP
FOR ALL OF ALASKA THROUGH THE WEEKEND.

BERING SEA/ALEUTIANS/SOUTHWEST ALASKA FORECAST...THE CURRENT ALEUTIAN
LOW IS BRINGING A WHOLE HOST OF HEADLINES TO THE WESTERN AOR.
BLIZZARD WARNINGS ARE BEING CONTINUED FOR 181/185/187/191. IN GENERAL
WE/VE FOLLOWED THE GFS SOLUTION IN THE GOING FORECAST PACKAGE...THERE
APPEAR TO BE ONLY MINOR DIFFERENCES IN THE NUMERICAL SOLUTIONS AND
THE GFS HAS BEEN THE GOING MODEL OUT WEST AS OF LATE. AS SUCH...WE
EXPECT THE PRECIPITATION AT THE PRIBILOF ISLANDS TO BE A BIT MORE
DELAYED THAN PREVIOUS THOUGHT AND HAVE ACCORDINGLY HELD OFF THE
BLIZZARD WARNING TILL MIDDAY ON THURSDAY FOR 195. FOR THE CENTRAL AND
EASTERN ALEUTIANS THE TIMING AND POSITION OF THE OCCLUSION MEANS THE
DIFFERENCE BETWEEN RAIN AND SNOW TONIGHT MAKING FOR A TRICKY
FORECAST. CURRENT THINKING IS THAT THE OCCLUSION WILL MOVE THROUGH
COLD BAY WEDNESDAY MORNING AND CHANGE THE PRECIPITATION TYPE FROM
SNOW TO RAIN...WHILE FURTHER WEST THE OCCLUSION WILL STALL JUST
BEFORE DUTCH HARBOR AS THE LOW MOVES EAST ALLOWING SNOW TO BE THE
PREDOMINANT PRECIPITATION TYPE THERE. THE EVENING SHIFT WILL HAVE TO
KEEP AN EYE ON THIS. FURTHER EAST BLIZZARD WARNING HAVE BEEN ISSUED
FOR WEST OF DILLINGHAM ON THURSDAY ALONG WITH A BLOWING SNOW ADVISORY
FOR COASTAL PORTIONS OF 155 WITH THE APPROACH OF THE ALEUTIAN LOW.

SOUTHCENTRAL FORECAST...SOME BREAKS IN THE CLOUDS THIS AFTERNOON
ACROSS COASTAL PORTIONS OF SOUTHCENTRAL ALASKA WILL GIVE WAY TO ALL
CLOUDS BY TOMORROW MORNING FOR THE ENTIRE EASTERN AOR AS THE ALEUTIAN
LOW STARTS TO AFFECT THE APPARENT WEATHER. HAVE ONLY SLIGHTLY TWEAKED
THE INHERITED GRIDS AS THEY LOOK ON TRACK. THE BIGGEST CHANGE IS WE
HAVE INCREASED THE WINDS ACROSS ALL OF SOUTHCENTRAL TOMORROW
AFTERNOON AND EVENING. THE 0Z PANC SOUNDING CONTINUES TO SHOW LOW
LEVEL MOISTURE ENTRENCHED BELOW 7500FT...THIS ACCOMPANIED BY LIGHT
WINDS AND SOME PARTIAL CLEARING AND/OR COLD AIR DRAINAGE TONIGHT
COULD SEE FOG FORMATION ACROSS USUAL FAVORED AREAS...INCLUDING THE
ANCHORAGE BOWL.

CLOUDS CONTINUE TO LOWER AND THICKEN ACROSS SOUTHCENTRAL ALASKA ON
THURSDAY AND PRECIPITATION SHOULD START EARLY THURSDAY MORNING AT
KODIAK AND SPREAD NORTHEAST TO COASTAL KENAI PENINSULA BY MIDDAY
TOMORROW. WE/RE EXPECTING KODIAK ISLAND/SEWARD/WHITTIER TO ACCUMULATE
SOME SNOW TOMORROW BEFORE CHANGING OVER TO ALL RAIN BY LATE THURSDAY
NIGHT. AS THE LOW TO THE WEST APPROACHES AND HIGH PRESSURE OVER THE
EASTERN INTERIOR PORTION OF THE STATE SLOWLY SLIDES EAST TO THE
YUKON...WINDS WILL PICK UP IN PORTAGE VALLEY AND TURNAGAIN ARM...A
BLIZZARD WARNING HAS BEEN POSTED FOR 125. THE OCCLUSION CONTINUES TO
SLIDE NORTHEAST DURING THE DAY TOMORROW ACROSS THE NORTHERN GULF OF
ALASKA...AS IT DOES SO AND APPROACHES THE COAST A BARRIER JET
DEVELOPS EAST OF PRINCE WILLIAM SOUND IN RESPONSE TO THE PARALLEL
ORIENTATION OF THE FRONT TO THE COASTAL MOUNTAINS. A HIGH WIND WATCH
HAS BEEN POSTED FOR 135. WARM AIR ADVECTION FOLLOWS THE FRONTAL
PASSAGE THURSDAY WITH WINDY CONDITIONS TOMORROW EVENING ACROSS MUCH
OF SOUTHCENTRAL ALASKA INCLUDING ANCHORAGE AND THE MATSU BOROUGH.
THIS WILL TRANSLATE INTO A DECENT CHINOOK EVENT FOR 1O1 INCLUDING
DRAINAGE OUT OF THE KNIK ARM NEAR PALMER AND BUTTE...A HIGH WIND
WATCH HAS BEEN ISSUED FOR 101. THE POSSIBILITY OF SOME COLD AIR
DRAINAGE ACROSS ANCHORAGE AND THE MATANUSKA VALLEY ALONG WITH THE
CURRENT COLDER AIR NOT FULLY BEING ERODED OUT COULD KEEP WEEKEND
TEMPERATURES NEAR THE 0C MARK THROUGH SUNDAY.

LONG TERM...THE MEAN UPPER TROUGH OVER THE ALASKA WEST COAST
CONTINUES TO MODULATE TO THE WEST AS THE STRONG UPPER LEVEL RIDGE
OVER SOUTHEAST ALASKA...A RIDGE THAT HAS BEEN PROGGED BY THE MODELS
FOR OVER A WEEK NOW...STRENGTHENS AND USHERS IN A MUCH WARMER REGIME
FOR NEXT WEEK AND POSSIBLY BEYOND. WITH A MEAN STORM TRACK ACROSS THE
EASTERN BERING SEA APPROACHING ON SOUTHWEST FLOW...AND WITH THE
STRONG RIDGE LOCATED TO THE EAST...A PERSISTENT FLOW OF MOISTURE
LOOKS TO SUPPORT A HEALTHY AMOUNT OF PRECIPITATION FOR SOUTHERN
COASTAL ALASKA ALONG WITH WINDY CONDITIONS THROUGH DAY 7.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 125 161 181 185 187 191.
         BLOWING SNOW ADVISORY 155.
         HIGH WIND WATCH 101 135.
MARINE...GALES 125 140 141 150 179 180 185.
         STORMS 120 130 132 138 155 160 165 170 171 172.
         HEAVY FREEZING SPRAY 138 140 141 160 165 179 185.

SDM JAN 07