Small Craft Advisory 565, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT MON JUL 20 2009

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL PATTERN CONTINUES TO TRANSITION...WITH THE UPPER LEVEL
RIDGE THAT WAS OVER THE INTERIOR SLIPPING EASTWARD INTO CANADA. A
LARGE UPPER LEVEL TROUGH IS LOCATED IN THE EASTERN BERING AND
CONTINUES TO MOVE TOWARDS MAINLAND ALASKA.

AT THE SURFACE...A NEARLY VERTICALLY STACKED LOW IS LOCATED IN THE
CENTRAL BERING AND IS MOVING EAST TOWARDS THE MAINLAND. GUSTY WINDS
AND RAIN ARE BEING REPORTED WITH THIS SYSTEM. A SURFACE FRONT IS
ACCOMPANYING THE EASTERN PERIPHERY OF THIS SYSTEM AND WILL CONTINUE
TO MOVE TOWARDS SOUTHWESTERN ALASKA.

.MODEL DISCUSSION...
IN THE SHORT TERM MODELS ARE IN GOOD AGREEMENT WITH THE STRENGTH AND
POSITION OF THE BERING LOW. BY THEN END OF THIS WORK WEEK SOME
SIGNIFICANT DIFFERENCES ARISE WITH THE POSITION OF THE LOW...WITH
BOTH THE EMCWF AND THE GFS HAVING DIFFICULTY RESOLVING THE LARGE
UPPER LEVEL TROUGH AND SHOWING DIFFERENT PLACEMENT OF THE SURFACE
LOW...BUT BOTH SEEM TO AGREE A LARGE AND SLIGHTLY WEAKER LOW WILL BE
LOCATED IN THE EASTERN BERING BY THE MIDDLE AND END OF THIS WEEK.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
RAIN WILL BE PREDOMINANT THIS WEEK AS THE BERING LOW CONTINUES TO
MOVE INTO SOUTHWESTERN ALASKA. WHILE RAIN SHOWERS WILL BE THE MAJOR
IMPACT THE FIRST PART OF THE WORK WEEK...A VERY IMPRESSIVE PRESSURE
GRADIENT SETS AS THIS LOW MOVES ONSHORE PRODUCING WIDESPREAD GUSTY
WINDS...ESPECIALLY ACROSS TURNAGAIN ARM. WINDS SHOULD BE BELOW HIGH
WIND WATCH/WARNING CRITERIA...BUT SHOULD BE GUSTING TO NEAR 55MPH.
WILL POST A WIND HEADLINE IN THE ZFP TO ADVERTISE THIS...AS WINDS OF
THIS MAGNITUDE IN JULY ARE UNCOMMON AND WILL HAVE AN ADVERSE IMPACT
ON THOSE WITH OUTDOOR ACTIVITIES.

IN ADDITION TO THE WIND THREAT ON LAND...GALE FORCE WINDS ARE LIKELY
ACROSS COASTAL WATERS OF SOUTHCENTRAL ALASKA...INCLUDING PRINCE
WILLIAM SOUND AND NORTHERN GULF OF ALASKA. GALE WARNINGS HAVE BEEN
ISSUED FOR THESE AREAS AND ROUGH SEAS WILL CONTINUE TO BE
HAZARDOUS...ESPECIALLY TO SMALL CRAFT.

.SOUTHWEST...
WHILE THE WIND THREAT WILL COME LATER IN THE WEEK FOR SOUTHCENTRAL
ALASKA...SOUTH CENTRAL ALASKA WILL EXPERIENCE THESE CONDITIONS
STARTING THIS AFTERNOON. AS THE SURFACE LOW APPROACHES THE MAINLAND
SOME POSSIBLE HEAVY RAIN WILL ACCOMPANY THIS SYSTEM...ALONG WITH GALE
FORCE WINDS. WINDS WILL INCREASE TODAY AS THE PRESSURE GRADIENT
TIGHTENS AND MAY EVEN GUST TO STORM FORCE. HAVE POSTED A GALE WARNING
TODAY FOR THE BRISTOL BAY AREA TO ACCOUNT FOR THIS THREAT. WHILE
WINDS WILL NOT BE AS STRONG LATER IN THE WORK WEEK...IT APPEARS THAT
GUSTY WINDS AND RAIN WILL REMAIN OVER SOUTHWESTERN ALASKA THROUGH AT
LEAST THE MIDDLE OF THE WEEK.

.BERING AND ALEUTIANS...
A CURRENT 995 MB LOW NEAR THE CENTRAL ALEUTIANS WILL CONTINUE TO MOVE
EAST AND DEEPEN. BY 00Z WEDNESDAY IT APPEARS THIS LOW WILL BE AROUND
975MB AT THE SURFACE AND BRING WITH IT SOME VERY GUSTY WINDS AND RAIN
TO THE ENTIRE BERING. BY TUESDAY GALE FORCE WINDS WILL BE PREDOMINANT
ACROSS MOST OF THE BERING AND ALEUTIAN ARC WITH GUSTS APPROACHING
STORM FORCE. NUMEROUS GALE WARNINGS REMAIN IN EFFECT FOR THE BERING
AND ALEUTIANS. WINDS SHOULD GRADUALLY DECREASE AS THE LOW WEAKENS BY
THE END OF THE WORK WEEK...BUT RAIN WILL REMAIN LIKELY AS SURFACE LOW
STALLS NEAR BRISTOL BAY.

.LONG TERM FORECAST...
BY THE END OF THE WORK WEEK THE BERING LOW IS EXPECTED TO WEAKEN THEN
RETROGRADE OUT INTO THE BERING. THERE ARE SOME DIFFERENCES BETWEEN
MODELS ON HOW STRONG THIS RETROGRADING LOW WILL BE AND HOW QUICKLY IT
WILL MOVE...BUT IT APPEARS THAT MOST OF SOUTHERN ALASKA WILL
EXPERIENCE RAIN AS THIS LOW MOVES OFFSHORE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 120 125 130 132 138 140 150 155 160 170 171 180 351 352

FIRE WEATHER...NONE

TARALDSEN JUL 09