High Wind in Alaska, September 24, 2013

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT MON SEP 23 2013

.ANALYSIS AND UPPER LEVELS...
AN ACTIVE WEATHER PATTERN CONTINUES ACROSS THE FORECAST AREA TODAY.
THE MULTI-DAY STORM IN THE GULF IS WEAKENING FROM THE TOP-DOWN...WITH
THE UPPER LEVELS NOW JUST AN OPEN WAVE AND THE SURFACE LOW FILLING
RAPIDLY. DEEP MOISTURE CONTINUES TO SPREAD BACK ALL THE WAY TO UPPER
COOK INLET...AND LIFT ASSOCIATED WITH AN EASTERLY SHORTWAVE HAS
BROUGHT THE FIRST ACCUMULATING SNOW OF THE SEASON TO PARTS OF THE
ANCHORAGE AND MAT-SU AREAS. A TRANSIENT RIDGE OF HIGH PRESSURE OVER
THE EASTERN BERING AND SOUTHWEST MAINLAND IS ALLOWING FOR SUNNY SKIES
AND SEASONABLY COOL TEMPERATURES. FURTHER WEST...A SUBSTANTIAL UPPER
TROUGH IS DIGGING ACROSS THE NORTHWEST PACIFIC WITH SATELLITE IMAGERY
BEGINNING TO SHOW A SURFACE LOW DEVELOPING IN THE VICINITY OF THE
LEFT-EXIT REGION OF A 145 KT JET STREAK CURRENTLY MOVING TOWARD THE
WESTERN ALEUTIANS.

.MODEL DISCUSSION...
WITH THE GULF LOW FINALLY WEAKENING ALL EYES TURN TO THE NEXT MAJOR
STORM CURRENTLY FORMING NEAR THE WESTERN ALEUTIANS. MODEL TRENDS IN
THE LAST 24 HOURS HAVE ALL BEEN TO SLOW DOWN THE SPEED OF THIS LOW.
WHEN COMPARED TO WATER VAPOR IMAGERY...THE DEEP MOISTURE BOUNDARY
ASSOCIATED WITH THE JET STREAM IS STILL FURTHER WEST THAN ALL OF THE
MODELS...MEANING THAT PERHAPS THE FORECAST WILL NEED TO BE SLOWED
DOWN EVEN FURTHER IN SUBSEQUENT FORECAST UPDATES. AS THIS LOW HEADS
EASTWARD...THE NAM BECOMES AN OUTLIER IN BRINGING THE UPPER LEVEL
LOW/WAVE INTO INTERIOR ALASKA AS OPPOSED TO MOVING INTO THE GULF.
THUS ON BOTH FORECAST DOMAINS THE GFS WAS THE PREFERRED MODEL...BOTH
SLOWING DOWN THE PROGRESS OF THE LOW AND INCREASING WIND SPEEDS
SLIGHTLY. THE NEXT STORM THAT FORMS ON THURSDAY OVER THE NORTHERN
BERING CONTINUES TO HAVE MORE SIGNIFICANT MODEL DISAGREEMENT. ALL
THAT CAN BE CONFIDENTLY SAID AT THIS POINT IS THAT A VERY STRONG 200
KT JET STREAM WILL BE FUELING THE DEVELOPMENT OF A STRONG LOW THAT
WILL DROP TOWARD THE BRISTOL BAY AREA SOMETIME THURSDAY NIGHT OR
FRIDAY MORNING.

.SHORT TERM FORECAST...
SOUTHCENTRAL...SKIES WILL CLEAR FROM WEST TO EAST THIS EVENING AS AN
UPPER TROUGH FINALLY PUSHES DEEP MOISTURE OUT OF THE AREA. THIS WILL
ALLOW THE BOTTOM TO FALL OUT FOR OVERNIGHT LOWS TONIGHT...ESPECIALLY
IN AREAS WITH SNOWFALL FROM TODAY...ALLOWING THE AREA TO EXPERIENCE A
HARD FREEZE AGAIN TONIGHT. THIS ALSO INCREASES THE LIKELIHOOD OF SOME
PATCHY FOG DEVELOPING LATE TONIGHT...MAINLY AROUND UPPER COOK INLET
WHERE PRECIPITATION HAS BEEN THE HEAVIEST. MOSTLY CLEAR SKIES SHOULD
CONTINUE ON TUESDAY AS HIGH PRESSURE AT ALL LEVELS MOVES THROUGH THE
AREA AHEAD OF THE RAPIDLY INTENSIFYING BERING SEA LOW. THE WEATHER
FRONT ASSOCIATED WITH THIS LOW WILL ENTER THE GULF BY WEDNESDAY
MORNING...ONCE AGAIN TIGHTENING PRESSURE GRADIENTS ACROSS THE
AREA...ESPECIALLY THROUGH THE FAVORED TERRAIN GAPS. CURRENTLY...IT
LOOKS LIKE WINDS THROUGH TURNAGAIN ARM WILL TOP OUT SHY OF WARNING
LEVELS...BUT IF MODELS TREND TOWARD THE 12Z NAM SOLUTION AND CARRY
MORE OF THE STORMS ENERGY INTO THE INTERIOR THESE SPEEDS WILL NEED TO
BE REVISED UPWARD.

SOUTHWEST MAINLAND...WINDS WILL START TO INCREASE ALONG THE COAST BY
TUESDAY MORNING AS THE BERING LOW GAINS STRENGTH. STRONG WINDS WILL
NOT MAKE MUCH PROGRESS INLAND AS THE FRONT STALLS ALONG THE
COAST...BUT A PERIOD OF RAIN WILL STILL LIKELY SPREAD INLAND ACROSS
MOST AREAS ON TUESDAY NIGHT. THE LOW CENTER ITSELF WILL FOLLOW A
TRACK ACROSS BRISTOL BAY AND INTO THE GULF...SIMILAR TO THE LAST
STORM...WHICH WILL KEEP MOST OF SOUTHWEST AWAY FROM THE STRONGEST
PORTIONS OF THE STORM WITH SHOWERS AND CLOUDINESS THE BIGGEST IMPACT.

BERING SEA AND ALEUTIANS...THE REGION WILL CONTINUE TO BE A SOURCE
REGION FOR STRONG LOW DEVELOPMENT THROUGH THE END OF THE WEEK. AS
MENTIONED ABOVE...THE FIRST LOW WILL BEGIN TO RAPIDLY INTENSIFY THIS
EVENING AND FOLLOW A SIMILAR TRACK TO THE PREVIOUS STORM. AS
SUCH...EXPECTING THE EASTERN ALEUTIANS TO AGAIN BEAR THE BRUNT OF
THIS STORM. SOME KEY DIFFERENCES...THOUGH...ARE THAT THE FORWARD
SPEED OF THE STORM ITSELF WILL BE SIGNIFICANTLY SLOWER WHICH WILL
MAKE IT HARD FOR WINDS TO BECOME TOO EXTREME. ADDITIONALLY...THE
STORM WILL HAVE PEAKED IN INTENSITY PRIOR TO REACHING THE DUTCH
HARBOR AREA. BOTTOM LINE: EXPECT WINDS TO INCREASE ONCE AGAIN BUT
LIKELY PEAK RIGHT AROUND HURRICANE FORCE (75 MPH)...THUS WILL BE
UPGRADING THE WATCH TO A WARNING FOR THE EASTERN ALEUTIANS. AS
MENTIONED...THE STORM WILL BE WEAKENING AS IT HEADS EASTWARD FROM THE
DUTCH HARBOR AREA...BUT MAY HOLD STRENGTH LONG ENOUGH TO ALSO BRING
HIGH WINDS TO THE ALASKA PENINSULA AREA...THUS WILL BE ISSUING A HIGH
WIND WATCH FOR THIS AREA.

.LONG TERM FORECAST...
THE LONGWAVE TROUGH LOOKS AS IF IT WILL STAY IN PLACE ACROSS MAINLAND
ALASKA THROUGH AT LEAST NEXT WEEKEND. THIS MEANS A CONTINUATION OF
THE ACTIVE STORM TRACK ACROSS THE BERING SEA THAT FEATURES STRONG
LOWS MOVING EASTWARD AND DROPPING INTO THE GULF OF ALASKA.
TEMPERATURES ACROSS THE MAINLAND WILL REBOUND TO NEAR-NORMAL ON
TUESDAY AS SOUTHERLY FLOW BEGINS TO BRING IN SOME WARMER AIR ALOFT.
HOWEVER...THIS WILL ALSO BRING IN CHANCES FOR RAIN STARTING MIDWEEK
AND CONTINUING THROUGH THE END OF THE WEEK...ESPECIALLY ALONG COASTAL
AREAS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 185
         HIGH WIND WATCH 181
MARINE...STORM 170 172
         GALE 120 130 132 150 155 160 165 171 175 176 179 180 185
FIRE WEATHER...NONE

AMD SEP 13