Small Craft Advisory 484, NWS Anchorage, AK

AREA FORECAST DISCUSSION...CORRECTION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT MON JUN 15 2009

.ANALYSIS...
WEAK HIGH PRESSURE IS IN PLACE ACROSS MOST OF SOUTHCENTRAL AND
SOUTHWEST ALASKA THIS MORNING. A WEAKENING 1011 MB LOW IS DRIFTING
SOUTHEAST TOWARD THE PANHANDLE WHILE A DEVELOPING SYSTEM SOUTH OF THE
ALEUTIANS IS THE MAIN FOCUS OF OUR ATTENTION. CURRENTLY...A 984 MB
STACKED LOW LOCATED AROUND 180W WHILE A TRIPLE POINT LOW RAPIDLY
DEEPENS SEVERAL HUNDRED MILES SOUTH OF THE ALASKA PENINSULA. THIS LOW
HAS BEEN THE CENTER OF THE DISCUSSION FOR MANY DAYS NOW...AS MODELS
HAVE HANDLED THIS DEVELOPING CENTER VERY POORLY.

UPPER AIR...
A DIRTY UPPER LEVEL HIGH CENTERED OVER THE UPPER KUSKOKWIM VALLEY
CONTINUES TO WEAKEN AS IT DRIFTS NORTHEAST TOWARD THE UPPER YUKON
VALLEY. A STRONG VORT MAX MOVING NORTH ON THE WESTERN PERIPHERY OF
THE HIGH ACROSS THE DELTA IS BRINGING RAIN TO A LARGE AREA OF THE
SOUTHWEST COAST...MUCH MORE THAN WAS ANTICIPATED. THERE IS THE
CONCENTRIC UPPER LOW SOUTH OF THE CENTRAL ALEUTIANS AND ANOTHER
STRONG WAVE THAT IS ASSOCIATED WITH THE DEVELOPING TRIPLE POINT LOW
SOUTH OF THE AKPEN. WORTH MENTIONING IS A SHARP TROF OVER EASTERN
SIBERIA. THIS TROF WILL PLAY A SIGNIFICANT ROLE LATER THIS WEEK AS IT
DIGS SOUTH OVER THE CENTRAL AND WESTERN BERING SEA.

.MODEL DISCUSSION...
MODELS ARE IN GREAT AGREEMENT BUT VARY DRASTICALLY FROM WHAT WE WERE
LOOKING AT THIS TIME YESTERDAY. FOUR RUNS IN A ROW NOW HAVE TRENDED
THE DEVELOPING TRIPLE POINT LOW BACK TO THE NORTHWEST INSTEAD OF
TAKING IT ACROSS THE SOUTHERN GULF. LAST NIGHTS SHIFT DID NOT FEEL
CONFIDENT ENOUGH TO CHANGE THE FORECAST BUT NOW ALL MODELS HAVE
ZEROED IN ON THIS SOLUTION INCLUDING NOGAPS AND THE CANADIAN. EVEN
THE MEMBERS OF THE GFS ENSEMBLE ARE AGREEING ON THIS LATEST TRACK.
GIVEN THE OVERWHELMING EVIDENCE...WE ARE BITING OFF ON THE NORTHWARD
TRACK WHICH WILL INCREASE THE WINDS SOUTH OF THE AKPEN TO GALES
TONIGHT.

STILL QUITE A BIT OF UNCERTAINTY BEYOND 60 HOURS. THE GFS AND EC ARE
IN RELATIVE AGREEMENT THAT THE AFOREMENTIONED COLD CORE LOW OVER
EASTERN SIBERIA WILL DROP SOUTHWARD MIDWEEK INTO THE CENTRAL BERING
SEA. THERE IS HOWEVER VERY LITTLE AGREEMENT IN THE HANDLING OF THE
SURFACE REFLECTION OF THIS LOW AND ITS NUMEROUS ASSOCIATED SHORT
WAVES. FOR A SMOOTHER TRANSITION INTO THE LONG RANGE FORECAST...WE
WILL BE USING THE 0Z ECMWF WHICH IS IN LINE WITH HPCS GUIDANCE FOR
THIS TIME FRAME.

.SHORT TERM FORECAST...
SOUTHCENTRAL...BESIDES MODEL DISCREPANCIES OVER THE GULF...THE MAIN
FOCUS OF THIS FORECAST PACKAGE WILL BE THE POTENTIAL CONVECTIVE
ACTIVITY THE NEXT COUPLE OF DAYS. THE 12Z SOUNDING IN ANCHORAGE STILL
DEPICTING ABUNDANT MOISTURE THROUGHOUT THE COLUMN. TEMPERATURES
BETWEEN 1000 MB AND 700 MB ARE 2 TO 4 DEGREES C WARMER THAN 24 HOURS
AGO WHILE TEMPERATURES ABOVE 700 MB REMAIN THE SAME. IF THE NAM
VERIFIES...850 TEMP WILL CONTINUE TO RISE ANOTHER 2 DEGREE C BY 06Z
THIS EVENING. THERE IS ALREADY VERY LITTLE CIN TO OVERCOME AND THE
THERMAL ADVECTION WILL HELP DESTABILIZE THE AIRMASS FURTHER THIS
AFTERNOON. IN ADDITION...SKIES ARE CLEARING NICELY SO WE ARE STILL
ANTICIPATING SHOWERS TO DEVELOP OVER THE MOUNTAINS THIS AFTERNOON AND
DRIFT WEST TO SOUTHWEST OVER THE VALLEYS. CAN ALREADY SEE CBS
DEVELOPING OVER THE COPPER RIVER BASIN SO A GOOD SIGN THAT THE MODELS
ARE ACCURATELY PREDICTING THE WIDESPREAD INSTABILITY THIS AFTERNOON.

TOMORROWS ACTIVITY WILL DEPEND LARGELY ON HOW MUCH DEBRIS CLOUDS
REMAIN AFTER TONIGHTS SHOWERS. AT THIS TIME...BELIEVE MOST OF
SOUTHCENTRAL WILL START OUT RATHER CLOUDY WITH BREAKS IN THE CLOUDS
SHOWING UP LATE MORNING TO EARLY AFTERNOON. IT APPEARS THAT
CONVECTION MAY BE LIMITED TO THE TALKEETNAS AND ALASKA RANGE TOMORROW
AS THE AXIS OF WARMEST AIR SHIFTS NORTHWARD OVERNIGHT. WILL WATCH
THIS CLOSELY BUT AT THIS TIME WILL KEEP THUNDERSTORMS OUT OF THE
ANCHORAGE AND KENAI PENINSULA FORECAST AFTER TONIGHT.

OUTSIDE OF THE CONVECTIVE THREAT THE NEXT COUPLE OF DAYS...SKIES WILL
BE PARTLY TO MOSTLY CLOUDY. LATER IN THE WEEK...A RIDGE DEVELOPS
ALONG THE GULF COAST WHICH COULD BRING BACK SOME BREEZY AFTERNOONS
AND EVENINGS TO THE AREA. SHOWERS WILL REMAIN ISOLATED TO SCATTERED
THROUGH THE REMAINDER OF THE WEEK.

SOUTHWEST INTERIOR...
AN UPPER LEVEL SHORT WAVE IS RESPONSIBLE FOR NUMEROUS RAIN SHOWERS
OVER THE KILBUCK AND AHKLUN MOUNTAINS THIS MORNING. THIS WILL DRIFT
NORTH AND WEAKEN THIS AFTERNOON AND OFFSHORE FLOW SHOULD
RESUME...DRYING AND WARMING THE SOUTHWEST INTERIOR. THE THERMAL
TROUGH AXIS DISCUSSED AT LENGTH IN THE SOUTHCENTRAL FORECAST EXTENDS
WEST OVER THE LOWER KUSKOKWIM VALLEY. SHOWERS AND THUNDERSTORMS ARE
POSSIBLE OVER MUCH OF THE INTERIOR THIS AFTERNOON AND TUESDAY. ON
WEDNESDAY...A SHORT WAVE ASSOCIATED WITH THE AKPEN LOW MOVES ACROSS
THE ALEUTIAN RANGE SPREADING STRONG SOUTHEASTERLY FLOW ACROSS THE
REGION. GAP WINDS WILL INCREASE WHILE CLOUD COVER REMAINS PRETTY
VARIABLE.

BERING SEA/ALEUTIANS...
THE MOST SIGNIFICANT CHANGES TO THE FORECAST WILL BE SEEN ALONG THE
ALASKA PENINSULA IN THE FIRST 36 HOURS AS WE TREND TOWARD THE NEW
SOLUTION. WINDS SOUTH OF THE AKPEN WILL INCREASE TO GALES THIS
EVENING. OTHERWISE RAIN...FOG...AND STRATUS WILL DOMINATE THE BERING
SEA AS IS TYPICAL FOR THE SEASON.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 155.
FIRE WEATHER...NONE.

AB JUN 09