Area Forecast Discussion
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FXAK67 PAJK 302155
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
155 PM AKDT THU JUL 30 2015

.SHORT TERM...AFTERNOON WATER VAPOR SATELLITE IMAGE SHOWS A BROAD
UPPER LEVEL SHORTWAVE TROUGH ACROSS THE GULF WITH A JET STREAM
HEADING TOWARD THE SOUTHERN PANHANDLE. THE ASSOCIATED SURFACE LOW
IN THE SOUTH CENTRAL GULF SLOWLY DRIFTS NORTHEASTWARD WITH A WARM
FRONT STRETCHES NORTHEAST FROM THE LOW CENTER TO THE SOUTHERN
PANHANDLE. UNDER DEEP SOUTHERLY ONSHORE FLOW...SHOWERS CONTINUE
ACROSS THE SOUTHERN HALF OF THE PANHANDLE WITH OCCASIONAL MODERATE
TO HEAVY RAINFALL RATE. NO SIGNIFICANT WINDS ARE OBSERVED...BUT UP
TO 20 KNOTS WINDS PREVAIL OVER THE SOUTHERN INNER CHANNELS.
AFTERNOON TEMPERATURES MOSTLY IN THE UPPER 50S TO THE LOWER 60S.
THE BROAD UPPER LEVEL SHORTWAVE TROUGH WILL BECOME NARROWER BY
FRIDAY MORNING AND SHIFT A LITTLE TO THE SOUTHEAST AS AN UPPER
RIDGE BUILDS OVER THE BERING SEA. NUMEROUS SHOWERS WILL CONTINUA
OVER THE SOUTHERN TWO THIRD OF THE PANHANDLE FRIDAY MORNING...THEN
DIMINISH BY THE LATE MORNING INTO THE EARLY AFTERNOON HOURS AS A
SURFACE HIGH PRESSURE BUILDS OVER THE SOUTHERN GULF THROUGH LATE
FRIDAY. DUE TO GLOOMY SKIES AND SHOWERS...DIURNAL TEMPERATURE
FLUCTUATION WILL BE SMALL. OVERNIGHT TEMPERATURES WILL BE
GENERALLY IN THE LOWER 50S AND FRIDAY HIGHS ONCE AGAIN IN THE
UPPER 50S TO THE LOWER 60S.

.LONG TERM...EXTENDED RANGE FORECAST PERIOD BEGINS WITH A VERY
LARGE UPPER TROUGH EXTENDING FROM THE NORTHWEST TERRITORIES WEST-
SOUTHWEST ACROSS THE GULF OF ALASKA AND THEN SOUTH OF THE
ALEUTIANS. SIGNIFICANT VORTICITY STREAMS ALONG THE SOUTHERN
PERIPHERY OF THE TROUGH AND SPINS UP TWO SEPARATE UPPER LOWS BY
SUNDAY AFTERNOON - ONE SOUTH OF THE ALEUTIANS AND THE SECOND WEST
OF THE DIXON ENTRANCE. THIS SECOND UPPER LOW REMAINS OVER THE
DIXON ENTRANCE THROUGH MID MORNING WEDNESDAY, THEN BEGINS TO TRACK
SOUTHEAST. DURING THIS SAME TIME FRAME, AN UPPER RIDGE BUILDS
UPSTREAM OVER THE WESTERN GULF AND BEGINS TO SHIFT TO THE EAST.
THE RIDGE SHOVES THE SECOND UPPER LOW OUT OF THE PICTURE BY
THURSDAY AFTERNOON, AND THEN MOVES OVER SOUTHEAST ALASKA BY THE
START OF THE WEEKEND AS THE FIRST UPPER LOW TAKES UP A POSITION IN
THE CENTRAL GULF.

AT THE SURFACE, BROAD HIGH PRESSURE DOMINATES MOST OF THE GULF,
THE SOUTHERN BERING SEA AND THE NORTHERN PACIFIC OCEAN. A WEAK
WARM FRONT ORIENTED EAST-WEST BISECTS THE LARGE SURFACE HIGH NEAR
48N. THIS FRONT CONTINUES TO MOVE EAST BEFORE GETTING CUT OFF FROM
THE PARENT LOW SUNDAY AFTERNOON BY SURFACE HIGH PRESSURE BUILDING
SOUTH FROM THE GULF. PRECIP FROM THIS FRONT BECOMES AUGMENTED BY
LARGE SCALE LIFT ASSOCIATED WITH THE SECOND UPPER LOW AS IT
APPROACHES THE OUTER COAST SUNDAY NIGHT AND WIDESPREAD SHOWERS
REMAIN OVER SOUTHEAST ALASKA SOUTH OF CAPE FAIRWEATHER THROUGH
NEXT THURSDAY NIGHT. LOOKS LIKE THERE WILL BE A BREAK IN THE
PRECIPITATION AFTER THAT ON FRIDAY, BUT IT WILL BE SHORT LIVED. A
FRONT AND SURFACE LOW ASSOCIATED WITH THE FIRST UPPER FEATURE WILL
THEN BE RIDING UP THE WEST SIDE OF THE SURFACE RIDGE AND SHOULD
ARRIVE ALONG THE OUTER COAST EARLY IN THE NEXT WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.

&&

$$

AHN/FRITSCH

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