Area Forecast Discussion
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FXAK67 PAJK 231345
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
545 AM AKDT SAT MAY 23 2015

.SHORT TERM...CURRENTLY A BIT OF CONVECTIVE ACTIVITY OVER THE FAR
SOUTHWEST PORTION OF THE SOUTHERN PANHANDLE...KLAWOCK
VICINITY...HAS SURVIVED THE NIGHT BUT APPEARS TO BE DISSIPATING.
MEANWHILE THE YAKUTAT AREA HAS LOW VIS IN FOG AND STRATUS WHILE
THE ANNETTE, KLAWOCK, SITKA AND KETCHIKAN AREAS HAVE SEEN A MARINE
PUSH WITH LOW CIGS. THIS WILL LAST FOR PROBABLY ANOTHER 6 HRS AT
YAKUTAT AND A FEW HOURS AT THE OTHER LOCATIONS. MADE FEW CHANGES
TO INHERITED FORECAST...DID UPDATE GULF WINDS TONIGHT AS NEW OFFSHORE
LOW CIRCULATION ON THE WEST BORDER IS A BIT MORE CLEARLY DEFINED
IN THE NEW MODEL RUNS. USED A NAM/EC COMBO ON THIS UPDATE AS WELL
AS FOR THERMODYNAMIC FIELD UPDATES. TODAY`S ROUND OF AFTERNOON AND
EVENING ISOLATED CONVECTION WITH ANOTHER LOW-RH DAY OVER ALL BUT
COASTAL AREAS OF PANHANDLE WILL AGAIN BE FOCUSED OVER THE EASTERN
PORTION OF THE SOUTHERN PANHANDLE INITIALLY. TEMPS WILL NOT BE AS
WARM AS YESTERDAY IN GENERAL THOUGH WITH INCREASED UPPER CLOUD
COVER ASSOCIATED WITH THE WEAK UPPER LEVEL CLOSED LOW OVER THE
SOUTHERN PANHANDLE. CONDITIONS DO NOT APPEAR FAVORABLE FOR STORM
MOVEMENT AS FAR WESTWARD TONIGHT WITH A SLIGHTLY MORE STABLE LAPSE
RATE IN THE MID-LEVELS. MODIFIED THE INHERITED THUNDERSTORM
COVERAGE TO EXPAND A BIT MORE WESTWARD IN THE SOUTH FOR TONIGHT
BUT NOT INTO ZONE 27...ONLY 26, 29 AND PORTIONS OF 28. LATEST
MODELS ALSO HIGHLIGHT AREAS EAST OF THE NORTHERN PANHANDLE AS MORE
ACTIVE TONIGHT. OFFSHORE LOW- LEVEL RIDGING WILL WEAKEN TONIGHT AS
A WEAK FRONT AND A BIT OF LIFT ALOFT BEGIN TO BRUSH THE WESTERN
PORTION OF OUR OFFSHORE AREA...WITH PRECIPITATION APPROACHING
YAKUTAT BY SUNDAY MORNING. TEMPERATURES WILL LIKELY COOL A FEW
DEGREES TODAY WITH HIGHS MOSTLY IN THE 60S AND A BIT MORE MID/UPPER
CLOUD COVER...UTILIZED MOS TO BUMP AREAS UP A COUPLE DEGREES ON
THE NORTH SIDE.

MARINE PUSH HAS THE POTENTIAL FOR MAKING IT FURTHER INLAND OVER
THE NORTHERN PANHANDLE TONIGHT AS THE RIDGE AXIS MOVES SLOWLY
EASTWARD...HOWEVER THE GRADIENT AND WIND SPEEDS WEAKEN AS THIS
HAPPENS. BEST GUESSES AT THIS POINT...YAKUTAT, GUSTAVUS, SITKA,
KETCHIKAN, ELFIN COVE AND KLAWOCK AREAS WILL SEE MARINE STRATUS.
WINDS IN THE CROSS SOUND AREA WILL LIKELY PICK UP AGAIN DUE TO SEA
BREEZES LATE THIS AFTERNOON BUT APPEAR LIKELY TO BE JUST BELOW
SCA- LEVEL. ALSO NORTHERN LYNN CANAL WILL LIKELY REACH 25 KTS OUT
OF THE SOUTH LATER TODAY AS THE GRADIENT TIGHTENS A BIT AND THIS
SHOULD LAST INTO TONIGHT. OFFSHORE...25KT WESTERLIES/NWLY`S ARE
LIKELY FOR ZONE 42 TODAY BUT SHOULD BE 20KTS GENERALLY IN 41, 43
AND 52.

TAIYA RIVER IN THE SKAGWAY AREA SHOULD BE MONITORED TODAY AS IT IS
CURRENTLY JUST BELOW ACTION STAGE DUE TO SNOW MELT. IT APPEARS TO
HAVE PASSED ITS DIURNAL MAX TODAY AND NO SIGNIFICANT PRECIP IS
EXPECTED INTO SUNDAY FOR THE DRAINAGE.

.LONG TERM...AN UPPER LOW CURRENTLY OVER WESTERN BRITISH COLUMBIA
WILL HAVE MOVED OFF TO THE SOUTHEAST BY THE START OF THE
EXTENDED RANGE FORECAST PERIOD AS AN UPPER LEVEL RIDGE SHIFTS TO
THE EAST. SITUATION AT THE SURFACE IS SIMILAR, WITH AN INVERTED
TROUGH OVER WESTERN CANADA MOVING SOUTHEAST AS A STRONG SURFACE
HIGH AND ASSOCIATED RIDGE SHIFTS EAST. PRIME MOVER FOR THESE
CHANGES IS A FRONT CURRENTLY ENTERING THE GULF FROM THE WEST. THE
ASSOCIATED LOW IS WELL TO THE WEST AND FORECAST TO REMAIN OVER THE
BERING SEA, SO THE FRONT ITSELF IS NOT EXPECTED TO VERY VERY
STRONG IN TERMS OF WIND OR PRECIPITATION AND A SIGNIFICANT PORTION
OF ITS AVAILABLE ENERGY WILL BE EXPENDED DISPLACING THE SURFACE
HIGH TO THE EAST. THAT SAID, RAIN IS FORECAST TO ARRIVE OVER THE
WESTERN PORTION OF ZONE 17 ON SUNDAY WITH LITTLE ADDITIONAL
PROGRESS TO THE EAST. HAVE CHANCE POPS REACHING AS FAR EAST AS
CAPE FAIRWEATHER BY MONDAY MORNING. APART FROM POSSIBLE RAIN IN
YAKUTAT, THE BIGGEST IMPACT OF THIS FRONT WILL BE AN INCREASE IN
CLOUD COVER SUNDAY NIGHT AND MONDAY OVER THE REMAINDER OF THE
PANHANDLE. BY TUESDAY, ANOTHER SURFACE HIGH IS FORECAST TO BUILD
IN OVER THE GULF FROM THE SOUTHWEST AND REMAIN IN PLACE FOR THE
REMAINDER OF THE WEEK. MODELS DIVERGE AT THAT POINT WITH ECMWF
BEING THE FAVORED SOLUTION. A WEAK UPPER LOW ASSOCIATED WITH THE
APPROACHING FRONT WILL TRACK TO THE EAST ALONG THE YUKON/BRITISH
COLUMBIA BORDER ON WEDNESDAY, BUT THE SURFACE HIGH OVER THE GULF
IS EXPECTED TO REMAIN STRONG AND IN PLACE AND THERMALLY INDUCED
LOW PRESSURE WILL PERSIST OVER BRITISH COLUMBIA. THUS, APART FROM
THE FRONT ON SUNDAY/MONDAY THE MAJORITY OF THE EXTENDED RANGE
FORECAST WILL BE A CONTINUATION OF WHAT WE HAVE BEEN SEEING
RECENTLY - A THREAT OF SHOWERS AND THUNDERSTORMS APPROACHING FROM
THE EAST IN THE AFTERNOONS, AND A DIURNAL MIGRATION OF THE MARINE
LAYER INTO THE INNER CHANNELS OVERNIGHT WITH VARYING DEGREES OF
CLEARING IN THE AFTERNOONS.

AN ENSEMBLE APPROACH WAS USED FOR PRESSURE AND WIND DIRECTIONS
THROUGH SUNDAY NIGHT, TRANSITIONING TO A BLEND OF ECMWF AND GFS
THROUGH WEDNESDAY NIGHT. WPC THEREAFTER. POP AND QPF FOR THE FRONT
ARE FROM SREF AND GFS. OVERNIGHT LOWS ADJUSTED PER BIAS CORRECTED
MOS WITH DAYTIME HIGHS DRAWING ON BOTH BIAS CORRECTED NAM AND BIA
CORRECTED GFS40. OVERALL FORECAST CONFIDENCE IS AVERAGE.

&&

.FIRE WEATHER...RELATIVE HUMIDITIES FORECAST TO REACH THEIR
MINIMUM VALUES TODAY WITH LOWEST VALUES OVER THE EASTER PORTIONS
OF THE PANHANDLE. MINIMUM VALUES DOWN TO THE LOW 20S EXPECTED
OVER THE FAR NORTHERN INNER CHANNELS, BUT WINDS NOT FORECAST TO BE
VERY STRONG, SO NO RED FLAG WARNING HAS BEEN ISSUED WITH THE
MORNING FORECAST. GREATEST THREAT OF FIRE THIS WEEKEND WILL COME
FROM HOLIDAY WEEKEND CAMPFIRES AND BON FIRES THAT ARE NOT WELL
TENDED TO AND SCATTERED TO ISOLATED AFTERNOON/EVENING THUNDERSTORM
ACTIVITY. FIRE DANGER SITUATION IMPROVES BEGINNING SUNDAY WITH MINIMUM
RH VALUES IN THE MID TO UPPER 40S. STILL NO SIGNIFICANT PRECIPITATION
EXPECTED ACROSS THE MAJORITY OF SOUTHEAST ALASKA, SO FUELS ON THE
FOREST FLOOR REMAIN DRY AND PRIMED TO BURN.

&&

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

&&

$$

WESLEY/FRITSCH

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