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FXAK67 PAJK 271410
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
610 AM AKDT THU AUG 27 2015

.SHORT TERM...A WEAK SHORT-WAVE PASSING ACROSS THE PANHANDLE
BROUGHT LIGHT TO MODERATE RAIN BANDS INTO THE NORTHERN PANHANDLE
OVERNIGHT. A SHARPER WAVE DIPS SOUTHEAST ACROSS SOUTHWEST
ALASKA...CROSSING THE ALASKA RANGE IN THE PROCESS...INTO THE GULF
THIS MORNING. WHILE THE INITIAL WAVE SPAWNED SURFACE LOW PRESSURE
OVER THE GULF. THE SECOND WAVE SERVES TO INTENSIFY IT AND ALSO
TAP SOME EXTRA-TROPICAL MOISTURE THAT HAS TRAVERSED EASTWARD FROM
THE SOUTHERN BERING SEA INTO THE SW GULF. BECAUSE OF THIS...WE
EXPECT RAIN TO INTENSIFY THROUGH THE DAY ACROSS THE NORTHERN
PANHANDLE. AN ASSOCIATED FRONT WILL BEGIN MOVING ONSHORE INTO THE
NORTHERN PANHANDLE THIS AFTERNOON AND STALL THIS EVENING BEFORE
WEAKENING TONIGHT. THEREFORE THE HEAVIER RAIN BANDS SPREAD INTO
THE CENTRAL AND SOUTHERN PANHANDLE TONIGHT. WE EXPECT 24 HOUR RAIN
AMOUNTS TO TOTAL AROUND 1 INCH FOR MOST OF THE PANHANDLE WITH
NOTABLE EXCEPTIONS OF NEAR JUNEAU OF BETWEEN 1 AND 2 INCHES OF
RAIN...AS WELL AS CONCERNING TOTALS OF 1 TO 1.5 INCHES IN THE
CHILKAT AND TAIYA RIVER BASINS. SEE HYDROLOGY.

AS THE LOW INTENSIFIES AND THE FRONT NEARS SHORE...A LOW LEVEL JET
DEVELOPS ACROSS THE NORTHERN AND CENTRAL PANHANDLE AROUND MIDDAY
AND WILL SLOWLY MIGRATE SOUTH AND EAST THROUGH TONIGHT. GRADIENTS
MAXIMIZE AROUND JUNEAU LATE THIS AFTERNOON INTO THE
EVENING...WHICH WILL SUPPORT STRONG WINDS FOR JUNEAU TO GUSTS TO
40 MPH. MEANWHILE...FORECAST REMAINS UNCHANGED FOR SKAGWAY FOR
STRONG WINDS TODAY...EVEN AS CONFIDENCE WEAKENING. WITH A LITTLE
MORE EASTERLY GRADIENT, WE ADDED SOME HIGHER GUSTS TO HAINES FOR
THE AFTERNOON. IN THIS TYPE OF SITUATION...SKAGWAY MAY BE BREEZY
BUT GUSTS TO 40 MPH MAY BE MORE DOUBTFUL BUT HAINES RECEIVES A BIT
MORE WIND. HOWEVER, THE NAM STILL SUGGESTING SKAGWAY COULD
HAPPEN...THUS WE HAVE NOT REMOVED THE THREAT. WE ALSO EXPECT GUSTS
TO 35 MPH OVER PRINCE OF WALES ISLAND LATE TONIGHT AND LIKELY
HIGHER GUSTS FOR KETCHIKAN AND ANNETTE ISLAND LATE AS WELL. THE
HAZARD MAP FEATURES A PLETHORA OF SMALL CRAFT ADVISORIES
INCREASING THROUGH THE AFTERNOON AND SLOWLY DISAPPEARING ACROSS
THE NORTH TONIGHT...WHILE INCREASING OVER THE SOUTH THROUGH
TONIGHT AS THE FRONT SLIDES EASTWARD. FINALLY...HIGH RES MODELS
GOING HARD FOR OUTFLOW WINDS OVER THE NORTHEAST GULF ON THE NORTH
SIDE OF THE LOW TONIGHT...SO MUCH SO THAT WE ADDED A SMALL CRAFT
TONIGHT FOR ZONE 51 OFFSHORE OF YAKUTAT FOR 30 KT. WE EXPECT GUSTS
TO 40 KT OUT OF DISENCHANTMENT BAY LATE TONIGHT AS WELL.

ACROSS THE NORTHERN PANHANDLE HIGH TEMPERATURES WILL EITHER CHANGE
LITTLE OR PERHAPS FALL THROUGH THE DAY AS RAIN RATES INCREASE.
TEMPERATURES WILL BE ANYWHERE FROM 50 TO 55 DEGREES OVER THE
NORTH...WHILE THE SOUTH WILL APPROACH 60.

USED ECWMF/NAM/NMM FOR UPDATES. RFC GRIDS WERE COMBINED WITH HIGH
RES NMM FOR QPF UPDATES. CONFIDENCE GENERALLY GOOD.

.LONG TERM...THE LOW DISCUSSED ABOVE WILL SHIFT SOUTHWARD THROUGH
THE EASTERN GULF ON FRIDAY. EXPECT THE HEAVIEST RAIN TO FALL OVER
THE SOUTHERN ZONES AND THE COASTAL MOUNTAINS. AS THE LOW
PROGRESSES SOUTH...THE FAR NORTHERN AREAS INCLUDING YAKUATAT WILL
SEE NELY OUTFLOW WINDS CAUSING THE RAIN TO DIMINISH OR END ALL
TOGETHER THROUGH THE DAY. ELSEWHERE THE RAIN WILL HAVE
TRANSITIONED TO SHOWERS DUE TO COLD AIR ALOFT WRAPPING AROUND THE
MAIN LOW. HAVE LEFT MENTION OF A SLIGHT CHANCE OF THUNDER IN THE
FORECAST FOR FRIDAY OVER THE OUTSIDE WATERS DUE TO THE DIFFERENCE
BETWEEN 850MB TEMPS AND WARM SST.

NORTH WINDS THROUGH THE INSIDE WATERS WILL INCREASE TO SMALL CRAFT
LEVEL IN LYNN CANAL FRIDAY MORNING AS THE LOW MOVES SOUTH OF
SITKA AND HIGH PRESSURE BUILDS TO THE NORTH. THE LOW LOOKS TO
WEAKEN ON SATURDAY BUT SHOWERS REMAIN IN THE AREA...THEN ANOTHER
LOW FORMS OVER THE NE GULF SATURDAY NIGHT REINTENSIFYING THE
RAINFALL AND MAY BECOME HEAVY AT TIMES AGAIN THROUGH SUNDAY. ON
MONDAY THE NEW LOW STARTS TO SHIFT SOUTH AGAIN AND ALLOWS RAIN TO
EASE OVER YAKUTAT AND THE NORTHERN PANHANDLE DUE TO OFFSHORE FLOW
AND WINDS AGAIN SHIFTED OUT OF THE NORTH. BY TUESDAY AFTERNOON
THE LOW WILL BE SOUTH OF THE AREA AND RAIN WILL BE ENDING IN
KETCHIKAN WITH WEDNESDAY LOOKING DRY AREAWIDE.

MODELS WERE IN GENERAL AGREEMENT WITH THE WET PATTERN THE NEXT
SEVERAL DAYS THEN THE DRYING TREND FOR THE MIDDLE OF NEXT WEEK
ALLOWING FOR GOOD FORECAST CONFIDENCE THERE. HOWEVER THERE WERE
FAIRLY LARGE DIFFERENCES ON LOW PLACEMENT AND
PROGRESSION/DEVELOPMENT OF THE SECOND LOW. THESE DIFFERENCES HAVE
THE BIGGEST IMPACT ON WINDS OVER THE OUTSIDE WATERS AND TIMING OF
WIND SHIFTS THROUGH THE INNER CHANNELS. FORECAST CONFIDENCE IN
THAT RESPECT IS LOWER.

&&

.HYDROLOGY...BOTH HIGH RES AND NAM UNCHARACTERISTICALLY ALLOWING
UP TO 1 TO 1.5 INCHES OF RAINFALL INTO THE TAIYA AND CHILKAT RIVER
BASINS THIS AFTERNOON. MODELS HAVE BEEN INSISTENT ABOUT IT MOST OF
THE WEEK. CONFIDENCE POOR IN GENERAL BECAUSE THIS IS NOT OUR
TRADITIONAL SETUP FOR HEAVY RAIN AS THE TROPICAL CONNECTION CAN
BEST BE DESCRIBED AS INDIRECT. NAM DOES INDICATE 700 MB FLOW
BACKING TO THE SOUTH THIS EVENING...BUT THAT DOES NOT EXPLAIN THE
HIGH RATES REPRESENTED FOR THIS AFTERNOON. BUT GIVEN THESE
EXPECTED AMOUNTS...WE DO EXPECT THE TAIYA NEAR SKAGWAY TO REACH
BANKFULL AND POSSIBLY REACH MINOR FLOOD STAGE TONIGHT. RAIN RATES
WILL BE MONITORED FOR POSSIBLE FLOOD WATCH ISSUANCE LATER THIS
MORNING OR A FLOOD ADVISORY THIS AFTERNOON FOR TONIGHT AFTER
COORDINATION WITH RFC. WITH HEAVY OROGRAPHIC ENHANCEMENT IN THE
MONTANA CREEK BASIN...WE ALSO EXPECT BANKFULL TO BE REACHED
TONIGHT...AGAIN WITH THE POSSIBILITY OF MINOR FLOOD STAGE. THE SPS
CONTINUES FOR NOW.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 4 PM AKDT THIS AFTERNOON THROUGH THIS EVENING
     FOR AKZ025.
         STRONG WIND FROM 10 AM THIS MORNING TO 4 PM AKDT THIS AFTERNOON
     FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012.
         SMALL CRAFT ADVISORY FOR PKZ011-013-022-031>036-041>043-051-052.

&&

$$

JWA/FERRIN

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