Small Craft Advisory 537, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT WED JUL 8 2009

.ANALYSIS AND UPPER LEVELS...
A POTENT UPPER LEVEL RIDGE IS CENTERED OVER EASTERN ALASKA TODAY
RESULTING IN CLOUD FREE CONDITIONS ACROSS MUCH OF THE EAST. MEANWHILE
AN UPPER LEVEL TROUGH IS LOCATED OVER THE BERING SEA AND AN UPPER
LEVEL SHORTWAVE TROUGH IS APPROACHING THE KUSKOKWIM DELTA FROM THE
WEST. A LOW PRESSURE IS CURRENTLY OVER CENTRAL ALASKA. A SHORTWAVE
ASSOCIATED WITH THIS LOW PRESSURE IS CAUSING RAIN TO FALL IN A BAND
ACROSS THE CENTRAL KUSKOKWIM VALLEY. AT THE SURFACE A HIGH PRESSURE
IS CURRENTLY LOCATED OVER THE CENTRAL ALEUTIAN ISLANDS RESULTING IN
WIDESPREAD STRATUS CLOUDS AND FOG ACROSS THE BERING SEA.

.MODEL DISCUSSION...
MODELS ARE IN RELATIVE AGREEMENT IN THE SHORT TERM WITH THE POSITION
OF THE UPPER LEVEL TROUGH AND REBUILDING OF THE UPPER LEVEL RIDGE.
MODELS BEGIN TO DIVERGE SUNDAY WITH THE GFS FAVORING A MORE NORTHERLY
TRACK THAN THE ECMWF FOR THE APPROACHING GULF LOW. THE GFS ALSO
INDICATES A SLIGHTLY STRONGER UPPER LEVEL RIDGE.

.SHORT TERM FORECAST...
THE UPPER LEVEL RIDGE CENTERED OVER EASTERN ALASKA WILL WEAKEN
BRIEFLY TODAY AS A SHORTWAVE APPROACHES BUT WILL SLOWLY BUILD INTO
THE REGION AGAIN THURSDAY NIGHT. A SHORTWAVE ASSOCIATED WITH THE
SURFACE LOW WILL BE THE FOCUS FOR POTENTIAL CONVECTION THIS AFTERNOON
OVER THE NORTHERN SUSITNA VALLEY AND COPPER RIVER BASIN. CONVECTION
WILL BUILD AGAIN THURSDAY OVER THE SUSITNA VALLEY AND THE CHUGACH
MOUNTAINS AND ACROSS THE COPPER RIVER BASIN AS AN ASSOCIATED TROUGH
STALLS OVER THE REGION.

TEMPERATURES OVER THE ANCHORAGE BOWL AND THE KENAI PENINSULA WILL BE
LOWER TODAY AS THE WEAKENING RIDGE WILL ALLOW FOR A STRONGER SEA
BREEZE TO DEVELOP. INCREASED CLOUD COVER AND SHOWERS ASSOCIATED WITH
THE APPROACHING SHORTWAVE WILL ALSO REDUCE TEMPERATURES.

HAZE AND SMOKE HAVE WORSENED OVER ANCHORAGE AS A NEW FIRE OVER THE
KENAI PENINSULA HAS INTENSIFIED AND GENERAL SURFACE SOUTHERLY FLOW
HAS DEVELOPED. VISIBILITY RESTRICTIONS AS A RESULT OF THE NEW FIRE
WILL FLUCTUATE OVER THE NEXT SEVERAL DAYS.

.SOUTHWEST...
NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS ASSOCIATED WITH A
SHORTWAVE TROUGH WILL CONTINUE TO TREK ACROSS THE KUSKOKWIM VALLEY
AND PROGRESS EASTWARD WITH THE TROUGH. DRYING OUT SHOULD OCCUR BEHIND
THE TROUGH AS A SURFACE HIGH PRESSURE PROPAGATES EASTWARD.

.ALEUTIANS AND BERING...
THE SURFACE HIGH PRESSURE OVER THE BERING SEA WILL PROGRESS NORTHWEST
OVER THE NEXT FEW DAYS. BY FRIDAY EVENING A LOW PRESSURE AND
ASSOCIATED FRONT FROM THE WEST WILL BEGIN TO INCREASE THE CHANCE OF
PRECIPITATION OVER THE WESTERN ALEUTIAN ISLANDS.

.LONG TERM FORECAST...
AN OVERALL PATTERN SHIFT WILL BEGIN TO OCCUR EARLY NEXT WEAK AS A LOW
PRESSURE SYSTEM APPROACHES MAINLAND ALASKA FROM THE WEST. MORE
SEASONABLE TEMPERATURES AND A GREATER CHANCE OF PRECIPITATION CAN BE
EXPECTED ACROSS MOST OF ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

ELN/AB JUL 09