Small Craft Advisory 109, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
220 PM AKST MON FEB 7 2011

.MODEL DISCUSSION...
SYNOPTIC SCALE INITIALIZATIONS ARE REASONABLE. FORECAST TRENDS ARE
GENERALLY GOOD AGREEMENT AND ARE ALSO REASONABLE.

.UPPER LEVELS...
STRONG 500 MB LOW CENTER WEAKENS AS IT MOVES TO THE CENTRAL AK PEN
TUE AFTERNOON. THIS CENTER CONTINUES TO WEAKEN AND TRAVERSES ACROSS
THE SOUTHERN MAINLAND AS AN OPEN WAVE WED. SHOULD SEE SIGNIFICANT
WARMING ACROSS THE SOUTHERN MAINLAND WITH THIS SYSTEM. 850 MB TEMPS
CONTINUE TO RISE TO AROUND 0 TO 2C OVER BRISTOL BAY TONIGHT AND 0 TO
-2C OVER THE NORTH GULF OF ALASKA TUE. TEMPS REMAIN RELATIVELY WARM
OVER SOUTHCENTRAL AND THE GULF THROUGH WED...BUT SHOULD START COOLING
AGAIN ACROSS SW AK AS COOLER AIR WRAPS IN BEHIND THE RETREATING WAVE.

THE 500 MB PATTERN REMAINS RELATIVELY PROGRESSIVE ACROSS THE MAINLAND
THROUGH THE LATTER PART OF THIS WEEK WITH SERIES OF MINOR WAVES
MOVING EAST.

.SURFACE...
WINDY...WARM...AND WET IS GENERALLY THE PATTERN EXPECTED OVER MUCH OF
THE SOUTHERN MAINLAND OVER THE NEXT 36 HRS. TEMPS SHOULD COOL OUT
WEST AND STRONG WINDS WILL DIMINISH OVER THE MAINLAND BY WED
MORNING...HOWEVER GENERALLY MILD CONDITIONS WILL CONTINUE OVER
SOUTHCENTRAL ALASKA INTO EARLY THU.

THE MAIN FEATURE OF IMPORTANCE IS A 970S MB LOW CENTER OVER THE NE
PACIFIC WHICH IS MOVING RAPIDLY NORTH. THIS CENTER IS EXPECTED TO
WEAKEN AND MAKE LANDFALL OVER THE AK PEN TUE MORNING. THE LOW WILL
CONTINUE TO WEAKEN AND MOVE ACROSS THE MAINLAND TUE. THE OCCLUDED
FRONT MOVES OVER THE AK PEN/ALEUTIANS THIS AFTERNOON AND INTO THE SW
MAINLAND AND WESTERN GULF TONIGHT. THE FRONT PROGRESSES EAST TO THE
NORTH GULF AND SOUTHCENTRAL AK TUE THEN HEADS EAST AND WEAKENS. HIGH
PRESSURE BUILDS OVER THE CENTRAL BERING SEA TUE THEN MOVES TO THE
WESTERN BERING SEA ON WED. A WEAK FRONT MOVES TO THE WESTERN
ALEUTIANS TUE EVENING THEN BECOMES DIFFUSE AS IT APPROACHES THE EAST
ALEUTIANS WED EVE.

.SOUTHCENTRAL ALASKA...
PRESSURE GRADIENTS WILL INCREASE ACROSS MUCH OF SOUTHCENTRAL
OVERNIGHT AND TUE. GALES AND STORM FORCE WINDS ARE EXPECTED IN
COASTAL MARINE AREAS AND GALES IN THE OFFSHORE MARINE AREAS OVERNIGHT
AND INTO TUE. INCREASING PRESSURE GRADIENTS WILL ALSO PRODUCE STRONG
GAP FLOWS THROUGH CHANNELED TERRAIN...ESPECIALLY IN THE
MAT-SU...ANCHORAGE BOWL...AND EASTERN KENAI PEN. WINDS ACROSS
TURNAGAIN ARM...PORTAGE...SHOULD BE FAIRLY STRONG BUT CURRENT
THINKING IS THAT IT WILL REMAIN BELOW WARNING LEVELS.  WINDS OVER
MOST AREAS WILL DIMINISH WED MORNING. PRECIPITATION ACCOMPANYING THE
FRONT WILL GENERALLY BE RAIN ALONG THE COASTAL AREAS WITH A
MIX INLAND...EXCEPT COPPER RIVER BASIN WHICH SHOULD BE GENERALLY
SNOW. THE POTENTIAL FOR ADVISORY LEVEL SNOWS OVER THE WESTERN SUSITNA
VALLEY LOOKS PROMISING FOR TUE WITH THE ONSET OF SE UPSLOPE FLOW
BEGINNING TUE MORNING. CONDITIONS BECOME MORE SHOWERY ACROSS MUCH OF
SOUTHCENTRAL WED.

.SW ALASKA...
EXPECT A BROAD AREA OF GALES FROM THE ALEUTIANS TO OVER MUCH OF
EASTERN BERING SEA OVER THE NEXT 24-36 HOURS. HIGH WIND CONDITIONS
LOOK PROMISING OVER THE NORTHERN BRISTOL BAY ZONE LATE TONIGHT INTO
TUE MORNING AS PRESSURE GRADIENTS AND LOW A LOW LEVEL JET ENHANCE GAP
FLOWS. THE HIGH WIND THREAT SHOULD END TUE AFTERNOON OVER BRISTOL
BAY. MOISTURE AHEAD OF FRONT IS ALREADY MOVING OVER THE AK PEN AND
EAST ALEUTIANS AND IS SHOWING SIGNS OF SPREADING INTO BRISTOL BAY.
MORNING SOUNDINGS SHOW FREEZING LEVELS OF AROUND 2200FT NEAR KING
SALMON AND 1600FT OVER BETHEL. THE MCGRATH SOUNDING SHOWS
SUB-FREEZING AIR BELOW 1600FT WITH ABOVE FREEZING AIR TO ABOUT
5700FT.

THINKING THE PRECIPITATION ACROSS THE AK PEN AND BRISTOL BAY WILL BE
MAINLAND RAIN...MAYBE MIXED NORTH INLAND BRISTOL BAY THROUGH TUE.
MIXED PRECIPITATION LIKELY ALSO OVER THE DELTA TUE. MAY SEE A FEW
POCKETS OF LIGHT FREEZING RAIN...MAINLY WEST OF BETHEL. WHILE THE
SOUNDING OVER THE KUSKOKWIM VALLEY SHOWS FREEZING RAIN
POTENTIAL...THE THOUGHT IS THAT DOWNSLOPE SHOULD MITIGATE
PRECIPITATION ACROSS THE VALLEY. PRECIPITATION SHOULD BECOME MORE
SHOWERY AND TREND TOWARD SNOW ON TUE NIGHT AND WED AS COLD AIR MOVES
IN FROM THE WEST.

.LONG TERM FORECAST...
ONCE FIRST STORM SYSTEM MOVES INLAND AND DISSIPATES...RESPITE WILL BE
BRIEF. AS A SECOND SYSTEM IS CLOSE ON ITS HEELS. SECOND SYSTEM WILL
FOLLOW A MORE EASTERLY TRACK...MOVING INTO THE GULF OF ALASKA INSTEAD
OF SOUTHWESTERN ALASKA. STRONG WARM ADVECTION AND GALE FORCE WINDS
ALONG AND AHEAD OF THIS SYSTEM AS WELL. ACTIVE PATTERN WILL PERSIST
INTO THE WEEKEND. UPPER LEVEL FLOW  WILL STEER NORTH PACIFIC SURFACE
LOWS INTO BOTH THE WESTERN ALEUTIANS AND DIRECTLY INTO THE GULF OF
ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH...161
MARINE...GALE WARNING...120 125 132 140 141 155 160 180 170 172
         STORM WARNING...130 138 150
         HEAVY SPRAY WARNING...185
FIRE WEATHER...NONE

RMC FEB 11