Flood in Alaska, August 12 to 13, 2014

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
223 PM AKDT MON AUG 11 2014

.SHORT TERM...A STATIONARY FRONT REMAINS OVER THE EASTERN GULF
WITH THE FRONTAL BOUNDARY EXTENDING WELL TO THE SOUTH AND A
SUBTROPICAL MOISTURE CONNECTION REMAINS WELL DEFINED IN AMSU DATA.
ANOTHER WAVE RIDING NORTH ALONG THE FRONTAL BOUNDARY WILL BRING
HEAVY RAIN TO PORTIONS OF THE PANHANDLE ONCE AGAIN TONIGHT.
HEAVIEST RAIN IS EXPECTED GENERALLY TO THE WEST OF CHATHAM STRAIT
AND EAST OF CAPE FAIRWEATHER, BUT WILL ALSO INCLUDE THE SKAGWAY
ZONE. THE TAIYA RIVER REMAINS NEAR BANKFULL AND THIS ADDITIONAL
RAINFALL MAY RESULT IN FLOODING. A FLOOD WATCH HAS BEEN INCLUDED
IN THE AFTERNOON FORECAST ISSUANCE.

THE STATIONARY FRONTAL BOUNDARY WILL FINALLY BEGIN TO WEAKEN BY
TOMORROW AFTERNOON. DRYING OUT AND PARTIAL CLEARING HAS ALREADY
BEGUN IN THE FAR SOUTHERN AND SOUTHEASTERN ZONES. VISIBLE
SATELLITE IMAGERY AND WEB CAMS ARE SHOWING THAT AREAS NEAR
KETCHIKAN AND MISTY FJORDS ENJOYED A FAIRLY NICE DAY TODAY. RAIN
ENDED EARLIER TODAY EAST OF CHATHAM STRAIT AND SOUTH OF FREDERICK
SOUND, BUT SKIES REMAIN MOSTLY CLOUDY TO OVERCAST. WITH PARTIAL
CLEARING LIKELY OVERNIGHT, PATCHY FOG IS EXPECTED TO FORM OVER
PORTIONS OF THE SOUTHERN PANHANDLE TONIGHT. FARTHER NORTH, IT
LOOKS LIKE THE JUNEAU AREA WILL BE LAST TO SEE THE RAIN
END...PROBABLY NOT UNTIL TUESDAY NIGHT.

WINDS REMAINED STEADY OUT OF THE SSE AT OR NEAR SMALL CRAFT LEVELS
FOR MOST OF THE DAY OVER CLARENCE STRAIT. EASTERLY WINDS 15 TO 20
KTS OVER CROSS SOUND. ALSO AM SEEING A NORTHERLY WIND OF 20 KTS
NEAR ROCKY ISLAND THIS AFTERNOON AND WAS OBSERVING AN EASTERLY
WIND OF 20 KTS ON THE THE SOUTH SIDE OF DOUGLAS ISLAND. THESE
WINDY SPOTS ARE EXPECTED TO RELAX THIS EVENING. ELSEWHERE, NO
SIGNIFICANT WINDS OVER THE INNER CHANNELS IN THIS SHORT TERM
FORECAST PERIOD. ON THE OUTSIDE, MAIN ISSUE IS RESIDUAL SEAS AT OR
ABOVE 8 FT FOR MUCH OF THE OUTER COAST THROUGH MUCH OF TOMORROW.
GULF WINDS 20 KTS OR LESS EXCEPT FOR 25 KT SOUTHEASTERLIES OVER
OFFSHORE ZONE 310.

USED NAM FOR UPDATES TO PRESSURE AND WIND. POP FROM A BLEND OF
GFS, GEM, AND ECMWF. QPF PER RFC AND ECMWF. FORECAST CONFIDENCE IS
AVERAGE.

.LONG TERM...MODELS REMAIN IN GENERAL AGREEMENT THROUGH THURSDAY
WITH AN UPPER LOW ACROSS ALASKA PENINSULA TUESDAY NIGHT SLOWLY
MOVES INTO THE WESTERN GULF WHILE AN UPPER HIGH PERSISTS OVER THE
WESTERN CANADA. A SURFACE RIDGE OF HIGH PRESSURE WILL CONTINUE TO
BUILD ACROSS THE EASTERN GULF AND PANHANDLE WITH CONTINUED DEEP
ONSHORE LOW TO MID LEVEL FLOW OVER THE AREA. REFRESHED THE
INHERITED FORECAST PACKAGE WITH THE NAM THROUGH THURSDAY FOR ITS
GOOD INITIALIZATION AND CONSISTENCY.

AS THE LOW IN THE WESTERN GULF DRIFTS NORTH...A FRONTAL PASSAGE
WILL AFFECT THE NORTHERN GULF. EXPECT CONTINUED WET PATTERN FOR
THE NORTHEASTERN GULF COAST WITH CATEGORICAL POPS THROUGH
THURSDAY. THE FRONT WILL ALSO PRODUCE SMALL CRAFT TO GALE FORCE
WINDS FOR THE OFFSHORE AND OUTSIDE WATERS THROUGH LATE THURSDAY.
THE RIDGE OF HIGH PRESSURE WILL MAINTAIN THE SOUTHERN PANHANDLE
GENERALLY DRY WITH SLIGHT CHANCE POPS. IN BETWEEN...NORTHERN AND
CENTRAL PANHANDLE WILL REMAIN WITH CHANCE POPS. CONTINUED ONSHORE
LOW TO MID LEVEL FLOW WILL KEEP SOUTHEAST ALASKA UNDER GLOOMY
SKIES.

FROM THURSDAY NIGHT ONWARD...MODEL DIFFERENCES BECOME LARGER BUT
GENERAL SYNOPTIC CONCEPT REMAINS THE SAME FROM THE PAST SEVERAL
DAYS. WITH THE UPPER LOW IN THE WESTERN GULF SLOWLY FILLS AND
DRIFTS NORTH TO THE WESTERN ALASKA. ANOTHER UPPER LOW OVER
KAMCHATKA WEDNESDAY MORNING WILL MOVE TO THE WESTERN TIP OF ALASKA
PENINSULA AND DEEPEN THROUGH THURSDAY NIGHT...THEN GRADUALLY MOVE
INTO THE WESTERN GULF BY SATURDAY NIGHT. THIS UPPER LOW WILL TRACK
NORTHEAST TO NEAR PRINCE WILLIAM SOUND THROUGH EARLY NEXT WEEK
WHILE SLOWLY FILLS. USED THE WPC ENSEMBLE SOLUTION FROM FRIDAY
THROUGH EARLY NEXT WEEK.

&&

.AVIATION...CONTINUED LOW VMC OR IMC CONDITIONS OVER THE NORTHERN
PANHANDLE THROUGH THE SHORT TERM WITH MOSTLY CLEAR SKIES AND LIGHT
WINDS OVER SOUTHEASTERN PORTIONS. PATCHY FOG OVER THE SOUTHERN
HALF AND ALONG THE OUTER COAST LATE TONIGHT INTO TOMORROW MORNING
WILL LIKELY BE A FACTOR TO EARLY MORNING AVIATION ACTIVITIES.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FLOOD WATCH THROUGH TUESDAY AFTERNOON FOR AKZ018.
MARINE...SMALL CRAFT ADVISORY FOR PKZ036-041.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ042-043-051-052.

&&

FRITSCH/AHN

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