Small Craft Advisory 465, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
535 AM AKDT THU JUL 7 2011

.ANALYSIS AND UPPER LEVELS...
AN UPPER-LOW NEAR THE SOUTHERN REACHES OF THE AK PANHANDLE CONTINUES
TO EJECT SOUTH AND AWAY FROM THE AOR. EMBEDDED SHORTWAVES STILL
ROTATE AROUND IT'S PERIPHERY...WITH CLOUDS AND SHOWERS PASSING FROM
NORTH TO SOUTH ACROSS THE COPPER RIVER BASIN. ACROSS THE REMAINDER OF
SOUTHCENTRAL...AN UPPER-RIDGE IS ESTABLISHED FROM THE SUSITNA VALLEY
DOWN THROUGH THE KENAI PENINSULA. AT THE SURFACE...A FRONT IS NEARING
THE SOUTHWESTERN GULF OF AK WITH RAIN. THE PRECIPITATION SHIELD WITH
THIS FRONT EXTENDS NORTH THROUGH BRISTOL BAY AND THE KUSKOKWIM DELTA.
THE PARENT LOW REMAINS NEARLY STATIONARY NEAR SAINT MATTHEW ISLAND.
FURTHER WEST...MORE RAIN IS SPREADING ACROSS THE WESTERN ALEUTIAN
CHAIN AHEAD OF A DEVELOPING WAVE OF LOW PRESSURE.

.MODEL DISCUSSION...
MODELS CAPTURE THE MAIN WEATHER FEATURES SATISFACTORILY AND ARE IN
MUCH BETTER AGREEMENT THAN THE PREVIOUS SEVERAL DAYS. AS SUCH
FORECAST CONFIDENCE IS HIGHER FOR THE NEXT FEW DAYS.

IN THE EAST...MODELS SHOW THE FRONT NEARING THE SW GULF WILL STALL
AND WEAKEN OVER THE SOUTHCENTRAL GULF ON FRIDAY AS A WAVE OF LOW
PRESSURE ALONG IT TRACKS SOUTH OF THE AOR. THEY ALSO AGREE ON THE
CONTINUANCE OF UPPER-LVL RIDGING BEING THE PRIMARY INFLUENCE OF
SENSIBLE WEATHER.

IN THE WEST...MODELS AGREE THAT THE SURFACE LOW NEAR SAINT MATTHEW
ISLAND WILL CONTINUE FILLING THROUGH TONIGHT. THEY ALSO SHOW THE WAVE
DEVELOPING OUT OVER THE WESTERN ALEUTIAN CHAIN QUICKLY ADVANCING EAST
WITH A CONSOLIDATED 995 MB CENTER NEAR THE PRIBILOF ISLANDS FRIDAY
MORNING...THEN TRACKING UP TO NEAR SAINT MATTHEW ISLAND ON SATURDAY
MORNING. THIS FEATURE APPEARS TO HAVE TRENDED A BIT STRONGER IN THE
SHORT TERM...SO THE SWATH OF FORECASTED GALES HAS BEEN EXTENDED A BIT
TO INCLUDE THE EASTERN ALEUTIAN CHAIN AND BERING TONIGHT.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
MARINE LAYER STRATUS HAS NOSED UP COOK INLET THIS MORNING...BUT IT'S
THIN NATURE COUPLED WITH DAYTIME HEATING SHOULD GIVE WAY TO SUNSHINE
FROM THE NORTHERN KENAI PENINSULA/ANCHORAGE BOWL UP TO THE MAT-SU
VALLEY. A FAIR AMOUNT OF SUBSIDENCE FROM THE UPPER-RIDGE SEEMED TO
RETARD THE NORMAL DIURNAL SHOWERS YESTERDAY...AND WITH NO APPRECIABLE
CHANGE EXPECTED DYNAMICALLY...BELIEVE CONDITIONS WILL REMAIN RATHER
DRY IN MOST LOCALES. SUBTLE WAVES ARE STILL ROTATING THROUGH THE
COPPER RIVER BASIN AND BRUSHING EASTERN PRINCE WILLIAM SOUND...WHERE
THE BEST CHANCES OF SHOWERS EXIST. IN ADDITION...STEADY RAIN WILL
OVERSPREAD KODIAK ISLAND AS THE FRONT NEARS...TAPERING TO SHOWERS BY
FRIDAY AS IT MOVES AWAY. ACROSS NORTHERN SECTIONS OF THE COPPER RIVER
BASIN...THERMAL TROUGH PROXIMITY AND MARGINAL INSTABILITY MAY STILL
YIELD SOME AFTERNOON/EVENING THUNDERSTORMS AS WELL...THOUGH THE
THREAT DIMINISHES BY FRIDAY WITH THE SAID TROUGH SHIFTING NORTH. HIGH
PRESSURE SUPPORTED BY THE UPPER-RIDGE EXPECTED TO PERSIST INTO THE
WEEKEND...WHICH LOOKS TO ALLOW FOR SEASONABLE TEMPERATURES AND FAIR
AMOUNTS OF SUNSHINE FOR A GOOD CHUNK OF SOUTHCENTRAL AK.

SOUTHWEST...
THE SUPPORTING SHORTWAVE ALOFT WILL ROTATE THROUGH THE SW MAINLAND
LATE TONIGHT WITH THE FRONT UNDERGOING FRONTOLYSIS AND RAIN TAPERING
TO SHOWERS. HOWEVER THE APPROACH OF THE NEXT SYSTEM ACROSS THE BERING
WILL BRING MORE STEADY RAIN TO THE KUSKOKWIM DELTA AND WESTERN
PORTIONS OF BRISTOL BAY/KUSKOKWIM VALLEY. ANOTHER ROUND OF GALE FORCE
WINDS IS ANTICIPATED FROM THE WESTERN CAPES OF BRISTOL BAY UP TO WEST
CENTRAL AK. LITTLE MOVEMENT OF THE PARENT UPPER-LOW IN THE NORTHERN
BERING SEA WILL KEEP A PERSISTENT ONSHORE FLOW WHICH WILL RESULT IN
COOL...CLOUDY AND WET CONDITIONS INTO THE WEEKEND.

BERING SEA/ALEUTIANS...
A FAST MOVING SLUG OF RAIN WILL OVERSPREAD THE ALEUTIAN CHAIN AS THE
WAVE OF LOW PRESSURE TRACKS ACROSS THE BERING THROUGH FRIDAY.
OTHERWISE TYPICAL FOG/STRATUS WILL CONTINUE ACROSS THE REGION.

.LONG TERM FORECAST...
ACROSS THE SOUTHERN MAINLAND...PERSISTENT UPPER-RIDGING LOOKS TO
CONTINUE INTO EARLY NEXT WEEK...WITH THE AXIS EVENTUALLY SHIFTING
EAST OF THE AOR AND ALLOW FOR A BIT MORE OF A MOIST FLOW TO DEVELOP.
THIS COUPLED WITH A MORE ZONAL FLOW MAY BRING A RENEWED CHANCE OF
STEADY PRECIPITATION. IN THE WEST...FORECAST CHALLENGES WILL LIE WITH
THE MOVEMENT AND POSITION OF THE RESIDUAL UPPER-LVL BERING LOW...
WHICH STILL LOOKS TO BE IN THE REGION NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...160 170 180 413 414
FIRE WEATHER...NONE

JAM JUL 11