Small Craft Advisory 606, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
705 AM AKDT MON AUG 12 2013

.ANALYSIS AND UPPER LEVELS...
THE LONGWAVE TROUGH WHICH HAD BEEN CENTERED OVER THE EASTERN BERING
SEA FOR THE PAST FEW DAYS HAS SHIFTED ITS POSITION WESTWARD THIS
MORNING AS THE ORIGINAL PARENT LOW MOVES NORTHWARD INTO THE CHUKCHI
SEA. TWO OTHER DISTINCT LOW CENTERS ARE PRESENT ACROSS THE BERING ON
SATELLITE IMAGERY...WITH ONE NEAR THE KAMCHATKA PENINSULA AND THE
OTHER CURRENTLY ENTERING THE SOUTHERN BERING TO THE WEST OF ADAK. AN
ASSOCIATED LARGE SUB 990 MB SURFACE LOW AND ACCOMPANYING GALE FORCE
FRONT ARE ALSO BEGINNING TO ENCROACH UPON THE SOUTHERN BERING AND
WILL SPREAD RAIN AND STRONG WINDS FROM THE CENTRAL AND EASTERN
ALEUTIANS TO THE PRIBILOF ISLANDS TODAY AS THEY MOVE SLOWLY NORTH AND
EASTWARD. MEANWHILE...SOUTHERLY FLOW CONTINUES TO SUPPORT WIDESPREAD
RAIN FROM THE KENAI PENINSULA INTO THE ANCHORAGE BOWL AND MAT-SU
VALLEY AS A SURFACE FRONT WEAKENS OVER THE NORTHWESTERN GULF.

.MODEL DISCUSSION...
MODELS HAVE GENERALLY COME INTO BETTER AGREEMENT REGARDING THE
OVERALL SYNOPTIC PATTERN THROUGH THE MIDDLE PART OF THIS
WEEK...ALTHOUGH THE NAM REMAINS SOMEWHAT OF AN OUTLIER IN TRYING TO
BRING THE SHORTWAVE MOVING THROUGH THE SOUTHWEST MAINLAND ON TUESDAY
TOO FAR TO THE EAST. THE GENERAL CONSENSUS IS FOR THE LOW CURRENTLY
AFFECTING THE ALEUTIANS TO MOVE INTO THE CENTRAL BERING BY TUESDAY
MORNING AND INTENSIFY WHILE REMAINING NEARLY STATIONARY THROUGH
WEDNESDAY AFTERNOON. THE VERTICALLY STACKED LOW WILL THEN BEGIN TO
MOVE EASTWARD TOWARDS THE NORTHERN PACIFIC LATER IN THE
WEEK...POTENTIALLY BRINGING INCREASED CLOUD COVER TO SOUTHCENTRAL AK.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
RAIN WILL BEGIN TO TAPER OFF ACROSS WESTERN PORTIONS OF SOUTHCENTRAL
AK BY THIS AFTERNOON AS WEAK RIDGING BUILDS IN FROM THE EAST AND THE
FRONT OVER THE NORTHERN GULF CONTINUES TO WEAKEN AND DISSIPATE. THE
DRYING AND WARMING TREND WILL CONTINUE INTO THE MIDDLE OF THE WEEK AS
RIDGING REMAINS IN PLACE. THIS WILL ALLOW DIURNAL CONVECTION AND WEAK
SEA BREEZES TO BECOME REESTABLISHED DURING THE MIDDLE TO LATER PART
OF WEEK.

SOUTHWEST ALASKA...
SHOWER ACTIVITY TODAY WILL BE LIMITED TO LOCATIONS NEAR THE ALASKA
RANGE AS WEAK TRANSITORY UPPER LEVEL RIDGING NOSES INTO THE SOUTHWEST
MAINLAND AHEAD OF THE AFOREMENTIONED BERING SEA LOW. ANOTHER ROUND OF
SCATTERED SHOWERS WILL BE POSSIBLE ON TUESDAY AS A WEAK SHORTWAVE
MOVES THROUGH FROM THE SOUTH...AND THEN AGAIN ON WEDNESDAY AS THE
BERING FRONT APPROACHES THE SOUTHWEST COAST.

ALEUTIANS/BERING SEA...
RAIN AND STRONG WINDS WILL BE ON THE INCREASE THIS MORNING FROM THE
CENTRAL AND EASTERN ALEUTIANS TO THE PRIBILOFS AS THE PREVIOUSLY
DISCUSSED SURFACE LOW AND ASSOCIATED FRONT TRACK NORTH AND EASTWARD
INTO THE BERING. WINDS WILL BEGIN TO SUBSIDE OVER THE EASTERN BERING
BY TUESDAY MORNING AS THE FRONT CONTINUES EASTWARD TOWARDS THE AKPEN.
HOWEVER...STRONG WINDS WILL PERSIST INTO TUESDAY NIGHT OVER THE
CENTRAL ALEUTIANS IN CLOSER PROXIMITY TO THE LOW AS IT MOVES INTO THE
CENTRAL BERING.

.LONG TERM FORECAST...
BY THE MIDDLE OF THE WEEK A LARGE VERTICALLY STACKED LOW WILL BE
ESTABLISHED OVER THE CENTRAL BERING...WITH WEAK HIGH PRESSURE
BUILDING IN EAST OF THE ALASKA RANGE. THE LOW WILL THEN DRIFT
SOUTHEASTWARD INTO THE NORTHEAST PACIFIC BY NEXT WEEKEND...BRINGING
SOME CLOUDS TO MUCH OF THE SOUTHERN MAINLAND BUT ALLOWING HIGH
PRESSURE TO BUILD INTO THE INTERIOR. OVERALL THIS WILL ALLOW THE
MAINLAND TO GET BACK INTO SOME DRIER WEATHER WITH A RETURN OF DIURNAL
CONVECTION AT INLAND LOCATIONS AND TEMPERATURES NEAR NORMAL. A RETURN
TO CALMER WEATHER BY THE END OF THE WEEK WILL LIKELY ALSO MEAN FOG
AND LOW CLOUDS BEGIN TO DEVELOP ONCE AGAIN IN THE BERING SEA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE WARNING 155 165 170 172 175 176 179 185
FIRE WEATHER...NONE

CB AUG 13

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1132 AM AKDT MON AUG 12 2013

AKZ181-130110-

...MINOR ASH FALL POSSIBLE NEAR PORT MOLLER AND NELSON LAGOON AND
BEAR RIVER...

WEB CAMERAS AND ALASKA VOLCANIC OBSERVATORY INDICATE THAT VENIAMINOF
VOLCANO HAS ERUPTED. WINDS WILL TRANSPORT THE ASH WEST TO NORTHWEST
WHICH COULD BRING SOME VERY LIGHT ASHFALL TO PORT MOLLER AND NELSON
LAGOON AND BEAR RIVER THROUGH THE LATE AFTERNOOON HOURS.