Small Craft Advisory 7, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1230 PM AKST THU JAN 1 2009

.ANALYSIS AND UPPER LEVELS...UPPER LEVEL BLOCKING PATTERN REMAINS
IN PLACE WITH A RIDGE OVER THE EASTERN BERING AND COMPLEX CLOSED
LOWS CENTERED OVER THE NORTHWEST PACIFIC AND NORTHERN CANADA. THE
SUB-TROPICAL IS WELL SOUTH OF ALASKA OVER THE NORTH PACIFIC. A
SHORT-WAVE IS CURRENTLY DROPPING DOWN THE EAST SIDE OF THE BERING
RIDGE ACROSS MAINLAND ALASKA...BRINGING A REINFORCEMENT OF ARCTIC
AIR WITH IT. TEMPERATURES ACROSS THE SOUTHERN MAINLAND ARE ALREADY
QUITE BRUTAL WITH WIDESPREAD VALUES OF 10 TO 30 BELOW AND VALUES
APPROACHING 50 BELOW IN THE COPPER RIVER BASIN. THERE IS SOME
LIGHT SNOW OUT AHEAD OF THE UPPER WAVE OVER THE KUSKOKWIM VALLEY.
STRATUS DOMINATES THE EASTERN BERING SEA UNDERNEATH THE RIDGE. OUT
WEST A STRONG VERTICALLY STACKED LOW IS NEARLY STATIONARY SOUTHWEST
OF THE ALEUTIANS. STORM FORCE WINDS ARE BEING OBSERVED JUST AHEAD
OF THE OCCLUDED FRONT ACROSS THE WESTERN ALEUTIANS. SATELLITE
IMAGERY SHOWS THIS FRONT BEGINNING TO ELONGATE AND STRETCH APART
AS THE SOUTHERN PORTION OF THE FRONT IS PUSHED RAPIDLY EASTWARD
BY THE UPPER JET. A WAVE HAS FORMED ON THE FRONT SOUTH OF ADAK
IS AND TRAVELING WESTWARD ALONG THE FRONT.

.MODEL DISCUSSION...MODELS INITIALIZED WELL WITH THE EXCEPTION OF
THE FRONTAL WAVE ALONG THE ALEUTIANS...WHICH NONE OF THE MODELS
PICKED UP ON. HOWEVER...DONT EXPECT THIS TO DEVELOP INTO ANYTHING
SIGNIFICANT. THERE ARE SOME MINOR MODEL DIFFERENCES WITH LOW
POSITION IN THE GULF IN THE SHORT-TERM...BUT IT WILL ONLY IMPACT
FORECAST FOR IMMEDIATE VICINITY...AS ALL OTHER AREAS WILL OBSERVE
COLD ADVECTION WINDS NO MATTER THE LOW POSITION. OUT WEST THERE
ARE MORE SIGNIFICANT DIFFERENCES WITH DEVELOPMENT OF A SURFACE LOW
EAST OF THE MAIN LOW AND TRACK TO THE WESTERN ALEUTIANS. WILL STICK
CLOSE TO CURRENT FORECAST WHICH IS CLOSE TO THE ECMWF AND REPRESENTS
A COMPROMISE POSITION BETWEEN THE GFS AND UKMET.

.SHORT TERM FORECAST...

SOUTHERN MAINLAND...THE BULK OF THE LOW LEVEL MOISTURE ASSOCIATED
WITH THE UPPER WAVE WILL GET CAUGHT UP ALONG THE ALASKA RANGE THIS
AFTERNOON AND TONIGHT. SOUTHCENTRAL WILL OBSERVE SOME MID TO HIGH
LEVEL CLOUDS AND MAYBE SOME FLURRIES AT HIGHER ELEVATIONS WHILE
SOUTHWEST ALASKA DRIES OUT. ARCTIC AIR ACCOMPANYING THE SHORT-WAVE
WILL QUICKLY ADVECT SOUTHWARD ACROSS THE REGION...RESULTING IN GUSTY
WINDS THROUGH MOUNTAIN PASSES AND ALONG THE GULF COASTAL WATERS.
THE COLD ADVECTION WILL AID IN DEEPENING OF THE EVER-PRESENT LOW
OVER THE GULF FRIDAY WHICH WILL IN TURN TIGHTEN UP THE PRESSURE
GRADIENT AND INCREASE WINDS FURTHER ALONG THE GULF COAST. ANOTHER
SHORT-WAVE WILL DROP DOWN FROM THE ARCTIC FRIDAY NIGHT AND
SATURDAY...THIS TIME FARTHER WEST AS THE RIDGE RE-FORMS BACK OVER
EASTERN SIBERIA IN RESPONSE TO BEING SQUEEZED BY CURRENT SHORT-WAVE
AND ALEUTIAN SYSTEM. THIS SECOND WAVE WILL DROP DUE SOUTH ACROSS
SOUTHWEST ALASKA SATURDAY AND ACROSS THE ALASKA PENINSULA SUNDAY
WITH AN UPPER LOW FORMING TO THE EAST OVER SOUTHCENTRAL. THIS WILL
TRANSPORT ARCTIC AIR SOUTHWARD ACROSS THE EASTERN BERING AND ALASKA
PENINSULA. A POSITIVELY TILTED TROUGH WILL ALLOW A LOW EMBEDDED IN
THE PACIFIC FLOW TO TRACK TOWARD SOUTHEAST ALASKA SUNDAY...WHICH
WILL ONCE AGAIN TIGHTEN UP THE GRADIENT AND STRENGTHEN THE WINDS
ACROSS SOUTHCENTRAL. THE VERY COLD AIR MASS WILL REMAIN IN PLACE
OVER MAINLAND ALASKA THROUGH NEXT WEEK.

BERING SEA/ALEUTIANS...THE COMPLEX UPPER LOW WILL REMAIN NEARLY
STATIONARY SOUTHWEST OF THE ALEUTIANS WHILE SHORT-WAVES EMBEDDED
WITHIN THE CYCLONIC CIRCULATION ALONG WITH THEIR SURFACE REFLECTIONS
WILL ROTATE ACROSS THE ALEUTIANS. THE DETAILS OF THESE FEATURES
WILL BE HARD TO NAIL DOWN VERY FAR OUT IN TIME. BOTTOM LINE THOUGH
IS STRONG FLOW WILL PERSIST BETWEEN THE LOW TO THE SOUTH AND RIDGE
TO THE NORTH AND EAST AND THE BULK OF THE PRECIPITATION WILL REMAIN
ALONG THE ALEUTIANS. THIS PATTERN WILL PERSIST INTO AT LEAST EARLY
NEXT WEEK.

.LONG TERM FORECAST...AS SHORT-WAVES CONTINUE TO DROP DOWN THE
EASTERN SIDE OF THE UPPER RIDGE NEXT WEEK IT WILL CONTINUE TO
RETROGRADE WESTWARD ACROSS RUSSIA. BY MID WEEK EXPECT A LONG-WAVE
TROUGH TO BE IN PLACE ACROSS THE ALASKA/BERING SEA REGION. THIS
MAY LEAD TO A MUCH MORE SIGNIFICANT CHANGE IN PATTERN BY THE END
OF NEXT WEEK AS THE TROUGH AMPLIFIES AND A RIDGE BEGINS TO BUILD
OVER THE EAST PACIFIC/WESTERN NORTH AMERICA. THIS WOULD ALLOW THE
STORM TRACK TO SHIFT BACK TOWARD MAINLAND ALASKA AND BRING A RETURN
TO MORE SEASONABLE TEMPERATURES.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...130 172 175 176 179 185.
         HEAVY FREEZING SPRAY WARNING...121 129 130 138 140 150 160
                                        179 185.
FIRE WEATHER...NONE.

SEB JAN 09