Area Forecast Discussion
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000
FXAK67 PAJK 111256
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
456 AM AKDT FRI JUL 11 2014

.SHORT TERM...A FRONT OVER THE EASTERN GULF WILL REMAIN NEARLY
STATIONARY DUE TO A RIDGE OF HIGH PRESSURE LOCATED OVER THE
PANHANDLE AND BLOCKING ANY SIGNIFICANT EASTWARD PROGRESS. NET
EFFECT OF THIS WILL BE A STEADY STREAM OF PRECIPITATION TRAINING
FROM SOUTH TO NORTH OVER THE COURSE OF THE SHORT TERM FORECAST
PERIOD. 24 HOUR PRECIPITATION FORECAST RANGING FROM ZERO FOR
LOCATIONS SOUTH AND EAST OF KUIU ISLAND TO 1.5 INCHES OR MORE IN
AND AROUND YAKUTAT. THESE NUMBERS ARE PREDICATED ON A GRADUAL
SHIFT TO THE EAST BY THE FRONT. IF THE RIDGE PREVENTS ANY
SIGNIFICANT MOVEMENT TO THE EAST, TOTAL RAINFALL WILL BE CONFINED
TO AREAS FURTHER WEST AND BE MORE THAN CURRENTLY FORECAST.

 WINDS ASSOCIATED WITH THE FRONT WILL BE LIMITED TO THE GULF FOR
THE MOST PART. HAVE EASTERLY 40 KT GALES IN THE FORECAST FOR
COASTAL MARINE ZONE 52 WITH LOWER VALUES TO THE SOUTH AND EAST.
MAX CONDITIONS EXPECTED TO OCCUR THIS MORNING AND GRADUALLY
DIMINISH THROUGH THE AFTERNOON AND OVERNIGHT. POSSIBILITY OF SOME
GUSTY CONDITIONS IN YAKUTAT, AND HAVE INCLUDED UP TO 19 KTS IN
THE TAF. ELSEWHERE, EASTERLY 20 KT WINDS OVER WESTERN ICY STRAIT
AND CROSS SOUND AND 15 KTS OR LESS FOR THE REMAINDER OF THE INNER
CHANNELS.

 FAIRLY SHARP FRONTAL BOUNDARY WILL LIKELY RESULT IN PARTLY
CLOUDY SKIES FOR SOUTHERN LOCATIONS WITH DAYTIME HIGHS RANGING
FROM THE UPPER 60S ALONG THE OUTER COAST TO THE MID 80S NEAR
HYDER. OVERCAST SKIES FARTHER NORTH WILL YIELD HIGHS IN THE UPPER
50S TO LOW 60S.

&&

.HYDROLOGY...MENDENHALL LAKE AND RIVER CONTINUE TO RISE AS A
RESULT OF SUICIDE BASIN DRAINING. AS OF 4 AM, THE STAGE OF
MENDENHALL RIVER WAS 10.8 FEET. FLOOD STAGE IS 11.5 FEET. AT THE
SAME TIME, MENDENHALL LAKE WAS AT 9.1 FEET, WHICH IS JUST ABOVE A
FLOOD STAGE OF 9.0 FEET. THE RISE IN MENDENHALL LAKE HAS BEEN VERY
RAPID AND STEADY OVERNIGHT, MATCHING THE RIVER FORECAST CENTER`S
MOST RECENT PROJECTIONS VERY CLOSELY. MAX FORECAST STAGE FOR THE
LAKE IS 11.99 FEET WHICH EXCEEDS THE PREVIOUS RECORD OF 11.2 FEET.
LIKEWISE, THE RIVER IS CURRENTLY FORECAST TO REACH 14.95 FEET,
WHICH IS MORE THAN A FOOT HIGHER THAN THE PREVIOUS RECORD. MANUAL
OBSERVATIONS OF THE RIVER OVERNIGHT ARE LAGGING BEHIND THE MOST
RECENT FORECAST. UNCLEAR AT THIS TIME WHETHER THIS SIGNALS A LOWER
MAXIMUM FLOOD OR A LATER TIME OF MAXIMUM FLOOD, OR BOTH. A DELAY
OF MAXIMUM FLOOD WOULD BE BENEFICIAL, AS IT WOULD OCCUR AFTER THE
AFTERNOON HIGH TIDE AND WOULD MITIGATE THE BACKWATER EFFECT ON THE
LOWER MENDENHALL RIVER. REGARDLESS, THIS WILL BE A HIGH IMPACT
EVENT WITH SOME LOCATIONS IN THE MENDENHALL VALLEY FLOODING FOR
THE FIRST TIME. LOCATIONS ALONG THE SWIFTLY FLOWING WATER OF THE
MENDENHALL RIVER WILL BE PARTICULARLY VULNERABLE TO EROSION.

&&

.LONG TERM...MODELS ARE IN GENERAL AGREEMENT THROUGH TUESDAY WITH
AN UPPER LEVEL LOW OVER THE WESTERN GULF SLOWLY DRIFTS
SOUTHWESTWARD WHILE AN UPPER HIGH ACROSS THE WESTERN CANADA MOVES
A LITTLE TO THE EAST. THE ASSOCIATED SURFACE LOW OVER BRISTOL BAY
ON SATURDAY MOVES SOUTHWARD ACROSS THE ALASKA PENINSULA OVER THE
WEEKEND AND FARTHUR SOUTH PASS 50N THROUGH TUESDAY...WHILE SURFACE
HIGH PRESSURE CONTINUES TO BUILD ACROSS THE ALASKA GULF. REFRESHED
THE INHERITED FORECAST PACKAGE WITH THE ECMWF AND GEM GLOBAL FOR
THEIR GOOD CONSENSUS IN SYNOPTIC SCALE THROUGH TUESDAY.

 AS THE LOW DRIFTS SOUTH...THE ASSOCIATED FRONTAL PASSAGE OVER
THE EASTERN GULF WILL WEAKEN THROUGH THE WEEKND. AS SUCH...LIKELY
TO CATEGORICAL POPS ACROSS THE NORTHERN HALF OF THE PANHANDLE WILL
GRADUALLY DIMINISH BY SUNDAY EVENING...YIELDING TO CHANCE POPS
OVERNIGHT SUNDAY NIGHT INTO MONDAY MORNING FOLLOWED BY GENERALLY
DRY WEATHER THROUGH TUESDAY. AS HIGH PRESSURE BUILDS ACROSS THE
GULF...THE GENERAL SOUTHERLY LOW LEVEL WINDS WILL BECOME NORTHERLY
ON SUNDAY AND SLIGHTLY INCREASE TO 15 TO 20 KNOTS THROUGH TUESDAY.

 MODEL SPREADS BECOMES LARGER BY MID WEEK WITH AN UPPER LEVEL
SHORTWAVE TROUGH DIGGING DOWN ACROSS THE WESTERN
ALASKA...SUBPRESSING THE RIDGE OVER THE GULF AND THE PANHANDLE
TOWARDS THE NEXT WEEKEND. THE ECMWF SHOWS A MORE PROGRESSIVE
PATTERN AND BRINGS THE UPPER LOW OVER THE NORTHERN GULF...WHILE
THE GFS KEEPS THE UPPER LOW FARTHUR NORTH OVER THE WESTERN ALASKA
INTERIOR. USED THE WPC ENSEMBLE SOLUTIONS INTO THE INHERITED
FORECAST PACKAGE FROM LATE TUESDAY THROUGH THE END OF THE LONG
TERM PERIOD. EXPECT GENERALLY DRY WEATHER CONTINUES WITH NO
SIGNIFICANT WINDS/SEAS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...AREAL FLOOD WARNING UNTIL 10 PM AKDT SATURDAY FOR AKZ025.
MARINE...GALE WARNING FOR PKZ043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ041-042.

&&

$$

FRITSCH/AHN






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