Area Forecast Discussion
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FXAK67 PAJK 042345
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
345 PM AKDT SAT JUL 4 2015

.SHORT TERM...UPPER RIDGE WILL CONTINUE BUILDING N INTO THE ERN
GULF AND SE AK THRU TONIGHT...THEN REMAIN THERE SUN. WEAK OCCLUDED
FRONT OVER THE CENTRAL GULF WILL DISSIPATE AS IT REACHES THE NRN
GULF TONIGHT. SFC HIGH WILL REMAIN OVER THE ERN GULF AND OUTER COAST
OF SE PUBLIC...WHILE AN INVERTED TROF DEVELOPS NWWD INTO THE SRN
PANHANDLE TONIGHT AND SUN. MODELS WERE FAIRLY CLOSE ON THE MAIN
FEATURES...AND ENDED UP BLENDING THE 12Z NAM WITH PREVIOUS
FORECAST FOR THE MOST PART.

MAIN FORECAST CONCERNS WILL BE CLOUD COVER...WINDS...AND TEMPS.
CLOUDS WITH THE WEAK FRONT OVER THE CENTRAL GULF WILL DRIFT N AND
E BUT GRADUALLY THIN OUT AS THEY MOVE ONSHORE. TRICKY PART OF THE
FORECAST IS HOW MUCH OF THESE CLOUDS WILL MOVE OVER THE AREA
TONIGHT AND SUN. THINK THERE WILL BE ENOUGH HIGH AND SOME MID-
LEVEL CLOUDS OVER THE NRN 2/3RDS OF THE AREA TO WARRANT A MOSTLY
CLOUDY FORECAST SUN...WITH CLOUDS INCREASING TONIGHT.
HOWEVER...WOULD NOT BE SURPRISED IF THERE ARE ENOUGH BREAKS/THIN
SPOTS TO ALLOW SOME SUNSHINE SUN. THERE MAY BE SOME LOWER MARINE
LAYER CLOUDS THAT AFFECT THE CENTRAL AND NRN COASTAL AREA
ESPECIALLY SUN...SO THEY WILL HAVE LESS CHANCE TO SEE SUNSHINE.
THE SRN AREAS SHOULD HAVE THE LEAST AMOUNT AND THINNEST
CLOUDS...SO WILL KEEP THEM PARTLY CLOUDY TO MOSTLY CLEAR FOR
TONIGHT AND SUN.

WINDS WILL BE DIMINISHING OVER MUCH OF THE INNER CHANNEL AREA
TONIGHT MAINLY DUE TO DIURNAL EFFECTS...ALTHOUGH ICY STRAIT COULD
SEE WINDS PICK UP THIS EVENING THEN DROP OFF AGAIN OVERNIGHT. KEPT
NRN LYNN CANAL BELOW SCA EARLY THIS EVENING AS PRESSURE GRADIENT
IS A BIT WEAKER THAN EXPECTED PREVIOUSLY. LOOKS LIKE STRONGER
WINDS WILL DEVELOP SUN AS INVERTED TROF INCREASES THE PRESSURE
GRADIENT OVER THE CENTRAL AND SRN AREAS AND ADJACENT ERN GULF
COASTAL WATERS. SERN GULF COASTAL WATERS WILL LIKELY REACH
SCA LEVELS AS WELL AS NW WINDS INCREASE THERE. THERE WILL BE A
BETTER CHANCE FOR NRN LYNN CANAL TO REACH SCA SUN AFTERNOON DUE TO
MORE HEATING THAN TODAY AND SOME SUPPORT FROM W-SW MID-LEVEL FLOW.

AS FOR TEMPS...THIS FORECAST MAY BE THE TRICKIEST OF ALL AS THEY
WILL HIGHLY DEPEND ON HOW THIN THE CLOUDS WILL BE TONIGHT AND SUN.
COMBINATION OF WARMER TEMPS ALOFT AND MORE CLOUD COVER SHOULD KEEP
LOW TEMPS TONIGHT HIGHER THAN THEY WERE THIS MORNING. FOR
SUN...USING 925 MB TEMPS AS A GUIDE...MOST PLACES OVER THE INNER
CHANNELS SHOULD GET INTO THE 70S DESPITE THE CLOUDS. THE FAR SERN
AREA COULD REACH 80-85...WARMEST NEAR HYDER. THE NRN AND CENTRAL
COASTAL AREAS SHOULD ONLY REACH THE 60S DUE TO POTENTIAL FOR SOME
MARINE CLOUDS IN THE AREA. ALL IN ALL...A NICE SUMMER DAY FOR THE
AREA SUN.

.LONG TERM...UPPER RIDGE REMAINS MAIN PLAYER OVER SOUTHEAST ALASKA
THROUGH TUESDAY. AS NOTED BY THE PREVIOUS SHIFT, MODEL SOLUTIONS
CONTINUE TO DIVERGE THEREAFTER BUT THERE HAS BEEN A TREND IN THE
LATEST GUIDANCE TOWARDS A DRIER TUESDAY-WEDNESDAY PERIOD. LATER IN
THE WEEK ONSHORE FLOW DOES INCREASE BUT STILL CONSIDERABLE SPREAD
IN THE MODELS. DUE TO ALL OF THIS HAVE CONTINUED A GENERAL
FORECAST OF MOSTLY CLOUDY AND CHANCE OF RAIN FOR THE NORTHERN HALF
OF THE PANHANDLE LATER TUESDAY THROUGH FRIDAY.

MONDAY WILL BE THE WARMEST DAY OF THE NEXT 7 FOR THE PANHANDLE.
WIDESPREAD 70 DEGREE WEATHER WITH THE POTENTIAL REMAINING FOR
INLAND LOCATIONS TO REACH 80 DEGREES. 850 MB TEMPERATURES WILL
RANGE FROM +15 TO 18 CELSIUS OVER THE AREA WITH AMPLE SUNSHINE. AS
THE RIDGE SHIFTS EAST THIS WILL SLOW MID AND HIGHER LEVEL CLOUDS
TO SPILL INTO THE AREA FROM THE WEST TUESDAY AND INTO WEDNESDAY
RESULTING IN COOLER AIR ALOFT AND HIGH TEMPERATURES ON AVERAGE 5
TO 10 DEGREES LOWER THAN MONDAY. EXPECT A SLOW COOLING TREND TO
CONTINUE THROUGH THE REMAINDER OF THE WEEK. AS MENTIONED ABOVE,
RAIN CHANCES WILL INCREASE THROUGH THE WEEK BUT AM LEANING TOWARDS
A DRIER MID WEEK PERIOD. THIS IS SUPPORTED BY THE 12Z ECMWF AND
GEM MODEL RUNS AND HAS BEEN ADVERTISED BY THE GFS FOR SEVERAL
RUNS. HAVE KEPT A CHANCE OF RAIN OVER THE NORTHERN PANHANDLE FOR
TUESDAY-WEDNESDAY BUT ANY RAIN THAT DOES OCCUR IS EXPECTED TO BE
LIGHT. AFTER MID WEEK THERE ARE A LOT OF WEAK FEATURES THAT THE
MODELS ARE HAVING TROUBLE WITH WHICH IS LEADING TO A LOT OF MODEL
SPREAD. REGARDLESS, DO NOT EXPECT ANY SIGNIFICANT WEATHER SYSTEMS
TO IMPACT THE AREA THROUGH FRIDAY AND ANY RAINFALL WILL LIKELY BE
ON THE LIGHTER SIDE.

WITH NO SIGNIFICANT SYSTEMS ON THE HORIZON WINDS WILL REMAIN
MAINLY THERMALLY DRIVEN WITH AFTERNOON SEA BREEZES AND LIGHTER
WINDS AT NIGHT. THERE WILL BE A BAND OF 25 KT SMALL CRAFT WINDS IN
THE SOUTHEAST GULF MONDAY NIGHT AS THE SURFACE RIDGE AND THERMAL
TROUGH TO THE EAST RESULT IN A TIGHTENED PRESSURE GRADIENT. THESE
WINDS WILL DIMINISH ON TUESDAY AS THE RIDGE WEAKENS AND SHIFTS TO
THE EAST.

USED THE 12Z NAM THROUGH 84 HOURS THEN THE LATEST WPC GUIDANCE FOR
THE REMAINDER OF THE EXTENDED RANGE. CHANGES IN THIS FORECAST
PACKAGE WERE MINIMAL AS UNCERTAINTY IN THE DETAILS REMAINS FROM
MID WEEK ONWARD.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-041-042.

&&

$$

RWT/TPS

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU





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