Brisk Wind Advisory 36, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1120 AM AKDT WED MAR 13 2013

.ANALYSIS AND UPPER LEVELS...THE BLOCKING RIDGE WHICH HAS BEEN OVER
THE BERING SEA THE PAST FEW DAYS IS LIFTING NORTHWARD INTO THE
ARCTIC. MEANWHILE A SHORT-WAVE OVER THE ARCTIC IS DROPPING DOWN THE
EAST SIDE OF THE RIDGE THIS MORNING ACROSS THE YUKON AND NORTHEAST
ALASKA. THIS IS BRINGING A REINFORCING SHOT OF ARCTIC AIR TO INTERIOR
ALASKA. THE SURFACE HIGH HAS ALSO BEEN RETREATING NORTHWARD ALLOWING
PRESSURE GRADIENTS ACROSS SOUTHCENTRAL TO SLACKEN AND WIND TO
DIMINISH. WITH COLDER AIR IN PLACE OVER INTERIOR SOUTHCENTRAL THERE
ARE STILL SOME LOCALLY STRONG GAP WINDS IN THE MAT VALLEY AND VALDEZ
AREAS.

.MODEL DISCUSSION...MODELS ARE GENERALLY IN GOOD AGREEMENT WITH
THE SYNOPTIC SCALE EVOLUTION OVER THE NEXT FEW DAYS. THERE ARE SOME
MINOR DIFFERENCES WITH LOW MOVING OUT OF THE NORTHEAST PACIFIC INTO
THE EASTERN GULF THURSDAY NIGHT. 12Z ECMWF AND GFS HAVE BOTH TRENDED
WESTWARD AND ARE IN GOOD AGREEMENT...SO WILL TREND FORECAST TOWARD
THIS SOLUTION.

.SHORT TERM FORECAST...THE SHORT-WAVE DROPPING INTO NORTHEAST ALASKA
THIS MORNING WILL TAKE A SOUTHWEST TRACK UNDERNEATH THE RETREATING
RIDGE THIS AFTERNOON THROUGH TONIGHT. BY THURSDAY MORNING THE RIDGE
WILL BE CENTERED OVER THE BEAUFORT SEA WITH A NEWLY FORMED UPPER LOW
SITTING UNDERNEATH IT OVER MAINLAND ALASKA. THIS WILL KEEP THE
STRONGEST COLD AIR ADVECTION OVER INTERIOR ALASKA. THE WEAKER COLD
AIR ADVECTION OVER SOUTHCENTRAL AND SOUTHWEST ALASKA WILL STILL BE
ENOUGH TO BRIEFLY KICK UP WINDS...PARTICULARLY THROUGH MOUNTAIN GAPS.
AS THE SHORT-WAVE REACHES SOUTHWEST ALASKA SOUTHERLY FLOW ALOFT WILL
ADVECT MOISTURE FROM THE GULF NORTHWARD OVER SOUTHCENTRAL. OFFSHORE
LOW LEVEL FLOW WILL MAINTAIN DRY LOW LEVELS SO ANY SNOW THAT DOES
FALL WILL BE VERY LIGHT. BLOWING SNOW WILL REDUCE VISIBILITIES
THROUGH PORTAGE VALLEY AND TURNAGAIN ARM...BUT DON'T EXPECT ENOUGH
WIND TO JUSTIFY AN ADVISORY. MEANWHILE...THE VALDEZ TO THOMPSON PASS
AREA WILL HAVE MORE WIND BUT EXPECT ONLY FLURRIES OR VERY LIGHT
SNOW...NOT ENOUGH TO CAUSE SIGNIFICANT VISIBILITY REDUCTIONS. AS THE
UPPER LEVEL LOW CONTINUES WESTWARD THURSDAY LIGHT SNOW WILL ALSO MOVE
INTO PORTIONS OF SOUTHWEST ALASKA. THIS LOW WILL WEAKEN AND EXIT TO
THE NORTHWEST ON FRIDAY AS THE PATTERN CONTINUES TO SHIFT.

MEANWHILE A STORM SYSTEM WILL TRACK OUT OF THE NORTHEAST PACIFIC
AND ACROSS THE EASTERN GULF THURSDAY NIGHT AND FRIDAY. RIDGING OUT
AHEAD OF IT WILL KEEP IT FROM TRACKING INLAND SO IT LOOKS LIKE IT
WILL STALL SOMEWHERE OVER THE NORTHERN GULF. THERE IS QUITE A BIT
OF UNCERTAINTY IN THE EXACT TRACK...BUT WITH CONTINUED OFFSHORE
FLOW OVER SOUTHCENTRAL AND PRECIP THAT DOES FALL WILL LIKELY BE
LIGHT AND FOCUSED NEAR THE LOW CENTER (PRINCE WILLIAM AREA).

TAKING A LOOK OUT WEST...AN ANCHOR LOW WILL REMAIN IN PLACE OVER
EASTERN RUSSIA WHICH MEANS STORMS WILL CONTINUE TO TRACK NORTHWARD
OVER THE FAR WESTERN BERING SEA. HOWEVER...AS THE RIDGE RETREATS
FROM THE BERING SEA FRONTAL SYSTEMS WILL NOW BE ABLE TO PROGRESS
EASTWARD. EXPECT ONE SUCH FRONT TO CROSS THE BERING THURSDAY AND
FRIDAY AND BRING SOME SNOW AND WIND TO THE SOUTHWEST COAST BY
FRIDAY NIGHT. MODELS ALL INDICATE MULTIPLE LOWS FORMING ALONG
THE FRONT AND HELPING TO TEAR THE FRONT APART BEFORE IT REACHES
SOUTHCENTRAL ALASKA.

.LONG TERM FORECAST...AS WE HEAD INTO EARLY NEXT WEEK MEDIUM RANGE
MODELS SUPPORT A RETURN TO A BLOCKING HIGH REDEVELOPING FROM THE
EASTERN BERING SEA ACROSS MAINLAND ALASKA TO THE ARCTIC. THIS WILL
CONFINE ACTIVE WEATHER TO THE WESTERN AND CENTRAL BERING AND
ALEUTIANS. MAINLAND ALASKA WILL STAY ON THE COLD AND DRY SIDE.
THERE IS POTENTIAL FOR ANOTHER WIND EVENT OVER SOUTHCENTRAL AND
THE GULF OF ALASKA DEPENDING ON PLACEMENT OF RIDGE AND ASSOCIATED
COLD ADVECTION DOWN THE EAST SIDE OF IT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...127 176.
         HEAVY FREEZING SPRAY WARNING...121 126 127 128 130 140 141
                                        160 165 179.
FIRE WEATHER...NONE.

SEB MAR 13