Area Forecast Discussion
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000
FXAK67 PAJK 120005
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
405 PM AKDT FRI JUL 11 2014

.SHORT TERM...AN OCCLUDED FRONT WILL REMAIN OVER THE ERN GULF
THRU SAT BUT WEAKEN SLOWLY. A LOW PRESSURE WAVE WILL MOVE N ALONG
THE FRONT INTO THE ERN GULF SAT. USED BLEND OF THE 12Z GFS/EC/GEM
THRU SAT AS THEY HAD GOOD AGREEMENT WITH THE MAIN FEATURES.

MAIN FORECAST CONCERNS WILL BE ONGOING FLOODING IN THE MENDENHALL
LAKE AND RIVER SYSTEM...PRECIP POTENTIAL/AMOUNTS...AND WINDS. WILL
DISCUSS THE FLOODING IN THE HYDROLOGY SECTION. AS FOR THE
PRECIP...MODELS HAVE DRIFTED SLIGHTLY TO THE E WITH THE ERN EDGE
OF THE PRECIP. LOOKS LIKE IT WILL REMAIN MOSTLY NW OF FREDERICK
SOUND...ALTHOUGH THE FAR WRN END OF FREDERICK SOUND OVER TO SRN
BARANOF ISLAND WILL BE IN ON THE ERN EDGE OF THE PRECIP. HEAVIEST
PRECIP SHOULD BE AROUND THE PAEL AREA WHERE STRONGEST LOW LEVEL
JET WILL REMAIN...BUT THIS JET WILL BE WEAKENING TONIGHT...SO
EXPECT PRECIP RATES TO DECREASE OVERNIGHT. THE LOW PRESSURE WAVE
WILL STRENGTHEN THE JET AGAIN SAT...SO PRECIP RATES SHOULD PICK UP
IN THE PAEL/PAGS AREAS. THE SERN EDGE OF THE PRECIP WILL LIKELY
SHIFT NW SOME AS WAVE MOVES N...SO AREAS AROUND PAGN WILL SEE
PRECIP DIMINISHING IN THE AFTERNOON.

WIND WISE...STILL HAVE SCA LEVEL E-SE WINDS AHEAD OF THE FRONT
OVER THE NRN/ERN GULF. THESE WINDS WILL SLOWLY DIMINISH BELOW SCA
LEVELS TONIGHT. HOWEVER...THE LOW PRESSURE WAVE WILL INDUCE A
SMALL AREA OF MIN SCA LEVEL S-SE WINDS AS IT MOVES NWD INTO THE
ERN GULF SAT. INNER CHANNEL WINDS ARE EXPECTED TO REMAIN BELOW SCA
LEVELS THRU SAT. MAY SEE 15-20 KT OVER NRN LYNN CANAL...CROSS
SOUND...AND AROUND CAPE DECISION THIS EVENING. NRN LYNN CANAL
WINDS SHOULD DROP TO AROUND 10 KT BY LATE TONIGHT...BUT PICK UP
AGAIN TO 15-20 KT SAT AFTERNOON.

OTHERWISE...THE FAR SERN AREA WILL ONLY SEE HIGH CLOUDS OVER THEM
ALTHOUGH SOME LOW STRATUS COULD AFFECT THE SRN OUTER COAST AND MAY
JUST GET INTO THE FAR SRN INNER CHANNELS TONIGHT. THINK ANY OF THE
LOW CLOUDS OVER THE S SHOULD DISSIPATE BY SAT AFTERNOON. LOOKS
LIKE A WARM DAY OVER THE SERN THIRD OF THE AREA...WITH TEMPS
GETTING INTO THE 70S THERE...WITH HYDER LIKELY REACHING THE LOWER
TO MID 80S. TEMPS OVER THE NRN AREAS WILL NOT DROP MUCH TONIGHT
ESPECIALLY WHERE IT HAS BEEN RAINING ALL AFTERNOON. ON SAT...NRN
AREA TEMPS WILL LIKELY ONLY RISE A FEW DEGREES.

&&

.HYDROLOGY...FLOODING HAS EXCEEDED THE 2011 GLACIAL DAM RELEASE
LEVELS AS OF 1 PM ON MENDENHALL LAKE AND RIVER. BOTH ARE STILL
FORECAST TO REACH RECORD HIGHS LATE THIS AFTERNOON...EXCEEDING AN
EVENT FROM SEPTEMBER 1995. THE PEAK OF THE EVENT IS EXPECTED
BETWEEN 4 PM AND 10 PM TONIGHT. THE RAIN FALLING IN THE AREA MAY
SLOW THE RATE OF FALL SOME LATER TONIGHT AND SAT...BUT A SHARP
DROP IS STILL EXPECTED. WILL MAINTAIN THE FLOOD WARNING FOR THE
MENDENHALL RIVER AND LAKE THRU 10 PM SAT. ONE OTHER AREA OF
CONCERN IS OVER THE FAR N. THE CHILKAT RIVER IS CURRENTLY
FORECAST TO GET TO MINOR FLOOD LEVELS SOMETIME SAT AFTERNOON OR
NIGHT...WHILE THE TAIYA RIVER IS FORECAST TO GET TO BANKFULL
LEVELS. CONFIDENCE IN THIS IS NOT VERY HIGH THOUGH...SO FOR THE
TIME BEING WILL NOT ISSUE ANY STATEMENTS FOR THE CHILKAT AND
TAIYA RIVERS.

&&

.LONG TERM...AN UPPER LEVEL LOW WILL REMAIN OVER THE ALASKA
PENINSULA SATURDAY NIGHT CAUSING S-SWLY ONSHORE FLOW OVER THE
PANHANDLE. RAIN DISCUSSED IN THE SHORT TERM SECTION WILL CONTINUE
FROM FREDERICK SOUND NW THROUGH SUNDAY. THE UPPER LEVEL LOW THEN TRACKS
SW DOWN TOWARD THE ALEUTIANS THROUGH SUNDAY WITH DECREASING
EFFECTS ON SE WEATHER AND DIMINISHING RAINFALL THROUGH SUNDAY NIGHT.

SURFACE HIGH PRESSURE BUILDS OVER THE GULF ON SUNDAY THEN REMAINS
IN PLACE THROUGH THE WEEK. THIS WILL AID IN THE DIMINISHING PRECIP
AND WILL CAUSE A NWLY FLOW OVER THE PANHANDLE IN THE LOWER LEVELS.
UPPER LEVEL ONSHORE FLOW BECOMES WEAKER THROUGH MID WEEK AND MORE
ZONAL. THEN THE SECOND HALF OF THE OF THE WEEK AN UPPER LEVEL
RIDGE OF HIGH PRESSURE STARTS TO BUILD IN THE GULF WHICH WOULD
AID IN THE DRYING EFFECT AS WELL.

MODELS DIVERGE MORE TOWARD NEXT FRIDAY AND INTO THE WEEKEND. THE
ECMWF BRINGS A NEW SYSTEM IN TO THE AREA EARLY FRIDAY WHILE THE
GFS HOLDS IT OFF UNTIL SATURDAY. USED A BLEND OF MODELS IN THE
SHORTER TERM WITH AN EMPHASIS ON THE GFS THEN TRANSITIONED TO MORE
NATIONAL WPC GUIDANCE FOR LATER PERIODS. FORECAST CONFIDENCE IS AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...AREAL FLOOD WARNING UNTIL 10 PM AKDT SATURDAY FOR AKZ025.
MARINE...GALE WARNING FOR PKZ051-052.
         SMALL CRAFT ADVISORY FOR PKZ041>043.

&&

$$

RWT/FERRIN





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