Area Forecast Discussion
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FXAK67 PAJK 041402
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
602 AM AKDT MON MAY 4 2015

.SHORT TERM...HIGH PRESSURE AT THE SURFACE EXTENDS FROM SOUTH
CENTRAL AK EASTWARD ACROSS THE YUKON AND NW TERRITORIES. SURFACE
LOW PRESSURE IS CENTERED 300 MI SW OF KETCHIKAN OFF THE BC COAST.
MID AND HIGH LEVEL CLOUDS CIRCULATING COUNTER CLOCKWISE AROUND
THE LOW CENTER ARE VISIBLE ON SATELLITE IMAGERY AS FAR N AS
PETERSBURG AND SITKA. N EDGE OF CLOUD SHIELD VERY THIN SINCE
METARS ARE REPORTING CLR SKIES. KEPT CHANCE POPS ACROSS THE FAR
SOUTHERN PANHANDLE TODAY BUT LOWERED RAIN AMOUNT IN GRIDS. THIS
LOW CENTER AND ASSOCIATED WEATHER WILL CONTINUE TO MOVE SLOWLY SE
AWAY FROM PANHANDLE LATE TONIGHT AND TUE.

THE HIGH PRESSURE TO THE NORTH IS CAUSING DRY NE TO SW WIND FLOW
AT LOW AND MID LEVELS. WEAK MOUNTAIN WAVE WIND EVENT APPEARS TO BE
OCCURRING OVER NORTHERN INNER CHANNELS. DOWNSLOPING WIND
PERIODICALLY PEAKING 30 TO 35 KT IN JUNEAU AND DOUGLAS WHERE
TEMPS REMAINED NEAR 50 OVERNIGHT. MEANWHILE IN WIND SHELTERED
AREAS TEMPS HAVE FALLEN TO FREEZING OR BELOW. HENCE THE UNUSUAL
COMBINATION OF HEADLINES FOR BOTH STRONG WIND AND FROST
ADVISORIES. WE DID REDUCE THE AREAL EXTENT OF FROST ADVISORY BY
CANCELING IT IN ZONES 26 AND 22. WE ALSO REMOVED
MENTION OF FOG THIS MORNING SINCE AIR MASS HAS DRIED CONSIDERABLY
SINCE SUNDAY.

TEMPS WILL WARM QUICKLY THIS MORNING WITH ABUNDANT SUNSHINE AGAIN
TODAY. STRONGEST WINDS SHOULD BE THIS MORNING IN INNER CHANNELS
BASED ON FORECAST PRESSURE GRADIENTS INCLUDING SCA FOR N LYNN
CANAL. OUTFLOW WINDS ALONG THE OUTER COAST MAY FLIRT WITH SCA
SPEEDS. USED PERSISTENCE IN INHERITED FORECAST EXCEPT FOR DRYING
FORECAST SLIGHTLY AS MENTIONED ABOVE GIVEN MODEL CONSISTENCY.
CONFIDENCE IN SHORT RANGE FORECAST THROUGH TUE REMAINS HIGH.

.LONG TERM...MODELS REMAIN IN FAIR AGREEMENT THROUGH THE MID WEEK
FOR A WEAK UPPER LOW OVER VANCOUVER ISLAND AND ITS ASSOCIATED
SURFACE LOW MOVE SOUTHEASTWARD TO THE PACIFIC NORTHWEST AS AN
UPPER RIDGE CONTINUES TO BUILD ACROSS THE CENTRAL AND EASTERN GULF
AND EXPANDS NORTHEASTWARD OVER THE PANHANDLE. REFRESHED THE
INHERITED FORECAST WITH THE ECMWF AND GEM GLOBAL FOR THEIR GOOD
CONSENSUS. DRY WEATHER WILL CONTINUE OVER SOUTHEAST ALASKA WITH A
PLENTY OF SUNSHINE AND LARGE DIURNAL TEMPERATURE FLUCTUATIONS.
DAYTIME HIGHS WILL BE MOSTLY IN THE MID TO UPPER 50S OVER THE
NORTHERN AND CENTRAL PANHANDLE TO AROUND 60 ACROSS THE SOUTHERN
AREAS. MOSTLY CLOUD FREE SKIES WITH RADIATIONAL COOLING AT NIGHT
WILL BRING OVERNIGHT TEMPERATURES TO THE MID 30S OVER THE NORTHERN
AREAS TO THE UPPER 30S TO THE LOWER 40S ACROSS THE SOUTHERN
PANHANDLE. RELAXED PRESSURE GRADIENT WILL RESULT NO SIGNIFICANT
WINDS.

MODEL DIFFERENCES BECOME LARGER ON HANDLING A DEVELOPING LOW FAR
SOUTH OF THE ALEUTIANS OVER THE SECOND HALF OF THE WEEK. USED THE
WPC GUIDANCE OF GEM BASED APPROACH FROM THURSDAY ONWARD. A
DEVELOPING UPPER LOW FAR SOUTH OF ALASKA PENINSULA WEDNESDAY NIGHT
WILL MOVE INTO THE WESTERN GULF BY LATE THURSDAY NIGHT...PUSHING
THE UPPER RIDGE EASTWARD OVER CANADA. THE ASSOCIATED SURFACE LOW
IN THE WESTERN GULF WILL MOVE NORTH NEAR KODIAK ISLAND THROUGH
LATE FRIDAY NIGHT...THEN WEAKEN ON SATURDAY AND DISSIPATE ON
SUNDAY. AS THE LOW APPROACHES KODIAK...A FRONTAL PASSAGE
ASSOCIATED WITH THE LOW WILL MOVE OVER THE OFFSHORE WATERS WITH
SMALL CRAFT LEVEL WINDS AND SEAS WEDNESDAY NIGHT INTO THURSDAY.
CLOUDS BEGIN INCREASING OVER THE EASTERN GULF AND THE PANHANDLE ON
THURSDAY...LEADING TO LIKELY POPS ACROSS THE NORTHEASTERN GULF
COAST...EXTENDING OVER GLACIER BAY TO NORTHERN BARANOF ISLAND
THROUGH FRIDAY. AS THE LOW WEAKENS AND DISSIPATES...SOUTHEAST
ALASKA WILL LIKELY TO RETURN ANOTHER PERIOD OF DRY WEATHER OVER
THE WEEKEND INTO EARLY NEXT WEEK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FROST ADVISORY UNTIL 8 AM AKDT THIS MORNING FOR AKZ017-019>021-
     025.
         STRONG WIND UNTIL 10 AM AKDT THIS MORNING FOR AKZ025.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-042.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041.

&&

$$

TA/AHN

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