Area Forecast Discussion
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FXAK67 PAJK 041338
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
538 AM AKDT TUE AUG 4 2015

.SHORT TERM...UPPER LOW WAS POSITIONED IMMEDIATELY ACROSS THE
BORDER FROM THE SERN TIP OF THE PANHANDLE EARLY THIS MORNING.
MULTIPLE VORTICITY LOBES CONTINUE TO ROTATE AROUND THE
LOW...SPREADING MID-HIGH LEVEL CLOUDS AND LIGHT ISOLATED TO
SCATTERED SHOWERS OVER THE SRN HALF OF THE PANHANDLE. THIS TREND
WILL CONTINUE DURING THE SHORT TERM PERIOD...WITH CLOUDS AND VERY
LIGHT SHOWER ACTIVITY FORECAST TO EXPAND NW TOWARD THE JUNEAU
AREA DURING THE LATE AFTERNOON THROUGH LATE NIGHT PERIOD.

MEANWHILE OVER THE NRN HALF OF THE PANHANDLE...MODEST LOW TO
MIDLEVEL OFFSHORE FLOW WILL PERSIST THROUGH THIS AFTERNOON...AND
THEN WEAKEN TONIGHT. SHORT TERM MODEL GUIDANCE SHOWS 850 MB
TEMPERATURES WARMING SEVERAL DEGREES HIGHER COMPARED TO
MON...WHICH WILL SUPPORT ANOTHER DAY OF HIGHS IN THE 70S.
HOWEVER...INCREASING HIGH LEVEL CLOUDS YIELD SOME UNCERTAINTY AS
TO EXACTLY HOW HIGH TEMPERATURES WILL BE. ATTM...EXPECT WARMEST
TEMPERATURES TO ONCE AGAIN BE INVOF HAINES /AROUND 80 F/ DUE TO
STRONGEST/MOST PERSISTENT DOWNSLOPE WINDS. MID TO UPPER 70S ARE
FORECAST ELSEWHERE FROM SKAGWAY TO JUNEAU...GUSTAVUS...AND HOONAH.

OTHERWISE...LOCALLY TIGHT PRESSURE GRADIENT OVER NRN LYNN
CANAL...AND OUTSIDE MARINE ZONES 41...42...AND 43...WILL YIELD
SMALL CRAFT WINDS DURING THE MORNING...AND THEN RELAX TO AROUND
20 KT DURING THE AFTERNOON. WINDS WILL WEAKEN FURTHER OVER THE NRN
INSIDE WATERS DURING THE EVENING BEFORE FLIPPING TO SLY
OVERNIGHT.

PRESSURE GRIDS WERE NUDGED TOWARD THE NAM AND ECMWF...THOUGH ARW
WINDS WERE LOADED AS A BASELINE FOR FURTHER LOCAL WIND EDIT. POP
AND QPF WERE UPDATED WITH A NAM/GFS/ECMWF BLEND.

.LONG TERM...A SHORT-WAVE CURRENTLY PASSING ACROSS THE RUSSIAN
ARCTIC WILL DIG EVER SOUTHWARD AS IT APPROACHES THE BROOKS RANGE
ON WEDNESDAY. THIS DIGGING WILL HELP SCOOT THE TWO RELATIVELY LAZY
UPPER LOWS AFFECTING THE PANHANDLE AND THE WESTERN GULF EASTWARD.
AS THE LOW OVER THE CENTRAL BC COAST DROPS SOUTHEAST WEDNESDAY...A
A WEAK DEFORMATION BAND MAY PROVIDE ENOUGH INSTABILITY TO SPARK A
FEW LIGHT SCATTERED TO ISOLATED SHOWERS STRETCHING NORTHWEST
PANHANDLE-WIDE ON WEDNESDAY...BUT MOST AREAS WILL STAY DRY. LOW
TO MID LEVELS WILL BACK TO ONSHORE ON WEDNESDAY. THIS WILL HELP
COOL TEMPERATURES A BIT AND WITH ADDED MOISTURE ALONG WITH THE
ADDITIONAL INSTABILITY ABOVE...AT LEAST THE NORTHERN PANHANDLE
WILL SEE CLOUDIER SKIES. COMPARED TO TEMPERATURES TUESDAY
AFTERNOON...WEDNESDAY TEMPS WILL BE AS MUCH AS 10 DEGREES COOLER
IN SOME LOCALES OVER THE NORTH WHERE DOWNSLOPE WINDS ARE SO
PREVALENT TODAY.

WEDNESDAY NIGHT WE TURN OUR ATTENTION TO THE WEST WHERE ANOTHER
MATURE UPPER LOW WILL BE DRAGGED BY THE SHORT-WAVE TO THE NORTH
ACROSS THE GULF. THE FORECAST HAS NOT CHANGED MUCH. AN ASSOCIATED
WEAK FRONT WILL BRING LIGHT RAIN TO THE COAST BY LATE WEDNESDAY
NIGHT AND TO THE REST OF THE PANHANDLE BY THURSDAY. TEMPERATURES
THURSDAY WILL BE RAIN-COOLED AND LIMITED AROUND 60 DEGREES. THE
LOW WILL MAKE VERY SLOW PROGRESS ACROSS THE GULF, AND WITH MOIST,
SOUTHERLY FLOW AHEAD OF IT...WE EXPECT RAIN CHANCES TO BE HIGH
THROUGH FRIDAY. AMOUNTS LOOK TO BE HIGHEST OVER THE CENTRAL AND
SOUTHERN PANHANDLE MAINLY THURSDAY NIGHT AND FRIDAY WHEN ONSHORE
COMPONENTS WILL BE GREATEST AND WHERE THE DEEPEST MOISTURE WILL
HAVE A DIRECT PATH.

DEPENDING ON THE TRACK OF THE LOW THERE LOOKS TO BE SOME BREAK FOR
THE PANHANDLE IN ITS LEE THIS WEEKEND...ESPECIALLY THE LATTER
PORTION BEFORE A WETTER SOUTHWEST FLOW REGIME SETS UP FOR NEXT
WEEK.

WINDS WILL GENERALLY REMAIN SOUTHERLY...EXCEPT FOR A BRIEF TIME
FRIDAY WHERE SOME WINDS SWITCH NORTHERLY AS THE LOW TRACKS TO THE
SOUTH. SOUTHERLY WINDS MAY STRENGTHEN AS THE FRONT APPROACHES THE
COAST THROUGH THE INSIDE CHANNELS WEDNESDAY THROUGH THURSDAY.
WHILE NOT RULING SMALL-CRAFT WINDS OUT OVER THE GULF...WHERE AND
WHEN THEY PICK UP IS MORE LIKELY QUESTION. GUIDANCE IS SKETCHY
AMONG SOLUTIONS. THE INSIDE FORECAST PAINTS A GENERAL PICTURE OF
THE BEHAVIOR OF FRONTAL WINDS THROUGH THE PASSAGES. CURRENTLY WE
HAVE A SMALL CRAFT FORECASTED FOR NORTHERN LYNN CANAL WEDNESDAY
AFTERNOON/EVENING. BUT CONFIDENCE PROBABLY FALLING AS MODELS SEEM
TO HAVE WEAKENED THE FRONT A BIT.

USED NAM/ECMWF FOR UPDATES WEDNESDAY/WEDNESDAY NIGHT WITH GFS AND
ECMWF THROUGH FRIDAY NIGHT. EXTENDED FORECAST UNCHANGED.
CONFIDENCE GENERALLY FAIR.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-041>043.

&&

$$

GARNER/ADKINS

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



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