Area Forecast Discussion
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FXAK67 PAJK 280019
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
319 PM AKST FRI FEB 27 2015

.SHORT TERM...A STRONG SURFACE HIGH OVER SOUTHWEST YUKON HAS A
RIDGE EXTENDING TO THE SOUTHEAST ACROSS NORTHERN BRITISH COLUMBIA.
AN INVERTED TROUGH EXTENDS NORTHWEST FROM VANCOUVER ISLAND AND
ALONG THE OUTER COAST OF SOUTHEAST ALASKA. A STRONG SURFACE HIGH
REMAINS LOCATED OVER THE CENTRAL GULF.

AN OFFSHORE FLOW REGIME EXISTS, BUT SURFACE WINDS HAVE NOT BEEN
MUCH TO SPEAK OF TODAY. STRONGEST OUTFLOW WINDS APPEAR TO BE
LOCATED NEAR THE COAST MOUNTAINS OF THE CENTRAL PANHANDLE. WINDS
AT FIVE FINGER LIGHT AT THE SOUTHERN END OF STEPHENS PASSAGE
THREATENED SMALL CRAFT EARLIER TODAY, BUT ARE DOWN TO 18 KTS AS OF
EARLY THIS AFTERNOON. EVEN SKAGWAY IS ONLY REPORTING A NORTHEAST
10 KT WIND. ACROSS THE CANAL, WINDS IN HAINES HAVE BEEN A BIT
STRONGER AT 16 KTS WITH GUSTS TO 26 KTS. ELSEWHERE, NO SIGNIFICANT
WINDS.

POP REMAINS WELL TO THE WEST WITH THE GULF HIGH SHUNTING
CLOUDINESS AND PRECIPITATION TO THE NORTH INTO THE COOK INLET AND
PRINCE WILLIAM SOUND AREA. VERY LITTLE EASTWARD PROGRESS BY THE
CLOUD SHIELD IS BEING OBSERVED IN SATELLITE IMAGERY. FARTHER
NORTH, SOME MID TO HIGH LEVEL CLOUDINESS IS MAKING IT OVER THE TOP
OF THE GULF HIGH, BUT MOST OF IT IS DISSIPATING AS IT DESCENDS
SOUTHEAST INTO THE YUKON AND BRITISH COLUMBIA. VISIBLE SATELLITE
IMAGERY IS NOT INDICATING ANY SIGNIFICANT CLOUDINESS OVER ANY
PORTION OF THE PANHANDLE. NOT A LOT OF CHANGE IS EXPECTED TONIGHT,
BUT THERE WILL BE AN INCREASE IN CLOUDS ALONG THE OUTER COAST
FROM YAKUTAT DOWN TO CAPE DECISION BY TOMORROW AFTERNOON AS A LOW
TO THE WEST RIDES UP AND OVER THE TOP OF THE GULF HIGH. PRECIP IS
EXPECTED TO REMAIN ENTIRELY WEST OF THE FORECAST AREA THROUGH THE
DAY, HOWEVER.

WITH NO CHANGE TO THE AIR MASS OVER SOUTHEAST ALASKA TONIGHT,
OVERNIGHT LOW ARE EXPECTED TO BE SIMILAR TO LAST NIGHT UNDER
MOSTLY CLEAR SKIES. DAYTIME HIGHS TOMORROW ALSO EXPECTED TO
SIMILAR TO TODAY, BUT THERE IS SOME UNCERTAINTY. A LOW LEVEL
TROUGH OF COLDER AIR IS BEING DEPICTED BY ALL MODELS AS RIDING UP
AND OVER THE HIGH IN THE GULF BY TOMORROW AFTERNOON. IF THIS
COLDER AIR REACHES DOWN TO THE SURFACE, FORECAST HIGHS FOR THE
NORTHERN HALF OF THE PANHANDLE MAY BE A BIT TOO WARM. EVEN SO,
SATURDAY LOOKS LIKE IT WILL BE A FINE DAY FOR OUTDOOR ACTIVITIES
ON LAND OR WATER, OR IN THE AIR.

USED A BLEND OF GEM AND ECMWF FOR UPDATES TO PRESSURE WITH NO
SIGNIFICANT CHANGES TO WINDS. POP AND QPF STILL NO FACTOR.
OVERNIGHT LOWS AND DAYTIME HIGH FROM PERSISTENCE. OVERALL FORECAST
CONFIDENCE IS ABOVE AVERAGE, BUT ONLY AVERAGE FOR TOMORROW`S HIGH
TEMPS.

.LONG TERM...A COUPLE OF FAIRLY WEAK SYSTEMS WILL MOVE THRU THE
RIDGE TOP SAT NIGHT AND SUN. LEAD SYSTEM WILL MAINLY HAVE JUST
SOME HIGH CLOUDS AND BE OUT OF THE AREA EARLY SAT EVENING. SECOND
SYSTEM WILL BE STRONG ENOUGH TO SUPPORT A WEAK SFC LOW THAT WILL
MOVE SE THRU THE ERN GULF SAT NIGHT AND SUN. MODELS SHIFTED THE
TRACK OF THIS LOW A BIT TO THE S ON LATEST RUNS. THIS LOW SHOULD
BE SE OF THE AREA BY LATE SUN AFTERNOON. UPPER RIDGE WILL REBUILD
OVER THE AREA SUN AFTERNOON INTO MON. FOR TUE INTO LATE
WEEK...MODELS DIFFER ON HOW MUCH ENERGY WILL GET THRU THE RIDGE
INTO THE AREA. ENDED UP USING A BLEND OF THE 12Z ECMWF AND GEM FOR
SAT NIGHT-MON...THEN WENT WITH MAINLY WPC FOR MON NIGHT ONWARD.

FOR SAT NIGHT AND SUN...LIGHT PRECIP WILL SPREAD ONSHORE MAINLY
OVER THE SRN 2/3RDS OF THE AREA SAT NIGHT. HAVE LOWERED POPS SOME
OVER THE FAR N TO CHANCE LEVELS OR LESS DUE TO THE SWD SHIFT IN
LOW TRACK. THIS SYSTEM WILL BE A FAST MOVER...AND PRECIP WILL
RAPIDLY COME TO AN END FROM N TO S SUN. THERE COULD BE A LITTLE
SNOW MIXED IN OVER THE NRN END OF THE PRECIP AREA BUT LITTLE
SNOW ACCUMULATION IS EXPECTED. WILL SEE CLOUDS DECREASE FROM THE N
SUN MORNING OVER THE NRN THIRD...THEN DURING SUN AFTERNOON OVER
THE CENTRAL THIRD OF THE AREA. THIS CLEARING TREND SHOULD REACH
THE SRN THIRD AROUND EARLY SUN EVENING. WINDS WILL INCREASE FROM
THE N SUN AS THE NLY PRESSURE GRADIENT BUILDS OVER THE AREA. WILL
LIKELY SEE SCA LEVEL N WINDS OVER THE FAR N BY SUN AFTERNOON.

FOR SUN NIGHT-MON NIGHT...WITH OFFSHORE FLOW AND A FAIRLY SHARP
RIDGE ALOFT TO THE W...LOOKS MAINLY CLEAR SKIES FOR THE AREA.
STRENGTHENING NLY PRESSURE GRADIENTS WILL INCREASE WINDS SUN NIGHT
INTO MON WITH SCA LEVEL NLY WINDS LIKELY OVER THE NRN INNER
CHANNELS. SOME COOLER AIR WILL MOVE INTO THE AREA AS WELL...WITH
DAYTIME TEMPS CLOSER TO NORMAL. NIGHTTIME TEMPS WILL BE FAIRLY
CHILLY IN WIND SHELTERED AREAS THOUGH UNDER THE MAINLY CLEAR SKIES.

FOR TUE ONWARD...INCREASING THREAT FOR PRECIP WILL DEVELOP DURING
MIDWEEK AS SHORTWAVES TRY TO BREAK THRU THE RIDGE ALOFT. MODEL
DIFFERENCES ON TIMING AND TRACK OF SYSTEMS CAUSED ME TO LIMIT
POPS TO LIKELY ON THE HIGH END THOUGH. LOOKS TO BE FAIRLY MILD
STILL DURING THE MID TO LATE WEEK TIME FRAME AS WARMER AIR MOVES
IN FROM THE SW...SO MUCH OF THE PRECIP SHOULD BE RAIN. MAY SEE
SOME SNOW OVER THE FAR NRN AREA HOWEVER.

&&

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

&&

$$

FRITSCH/RWT

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