Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
000
FXAK67 PAJK 032346
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
346 PM AKDT FRI JUL 3 2015

.SHORT TERM...UPPER RIDGE WILL BUILD N OVER THE ERN GULF AND SE AK
THRU SAT. WEAK OCCLUDED FRONT WILL MOVE N INTO THE CENTRAL GULF SAT.
SFC HIGH PRESSURE RIDGE WILL REMAIN OVER THE FAR ERN GULF AND SE
AK THRU SAT. MODELS WERE GENERALLY CLOSE ON THE MAIN FEATURES THAT
WILL AFFECT THE AREA...AND ENDED UP DOING A BLEND OF THE 12Z NAM
WITH PREVIOUS GRIDS FOR TONIGHT AND SAT.

MAIN FORECAST ISSUES WILL BE CLOUD COVER...WINDS...AND TEMPS.
WITH RIDGE ALOFT BUILDING INTO THE AREA...LOW LEVEL INVERSION WILL
GRADUALLY LOWER TONIGHT. BIG QUESTION IS WHETHER THIS WILL TRAP
SOME LOW CLOUDS UNDER IT OR IF SOME DRIER AIR WILL MINIMIZE THIS.
THINK THAT THE BEST CHANCE FOR LOWER CLOUDS TO REMAIN OR DEVELOP
TONIGHT IS ALONG THE CENTRAL AND NRN COAST INTO THE CENTRAL INNER
CHANNELS. THINK SOME OF THIS WILL BE FOG AS WELL...SO INCLUDED
PATCHY FOG FOR MAINLY THE N-CENTRAL INNER CHANNELS FOR LATE
TONIGHT. MAY SEE A THIN BAND OF LOWER CLOUDS DEVELOP ALONG THE
S-CENTRAL COAST MTNS LATE TONIGHT THAT AFFECTS PAPG AND POSSIBLY
PAWG. AM EXPECTING THE LOWER CLOUDS TO THIN OUT AND GENERALLY
DISSIPATE DURING SAT AS ENOUGH LOW LEVEL DRYING OCCURS. HIGHER
CLOUDS WILL MOVE IN MAINLY TO THE OUTER COAST SAT AHEAD OF WEAK
OCCLUDED FRONT. THINK ANY PRECIP WITH THIS FRONT WILL STAY OVER
THE CENTRAL GULF THRU SAT.

WINDS SHOULD GRADUALLY DIE DOWN TONIGHT ON THE INNER CHANNELS UNDER
THE SFC RIDGE. STILL...20-25 KT WINDS ARE EXPECTED EARLY TONIGHT
OVER LYNN CANAL AND UP TO 20 KT FOR THE FAR SRN INNER CHANNELS. ON
SAT...WINDS WILL PICK UP AS DIURNAL PROCESSES BEGIN TO DOMINATE
WITH MANY AREAS HAVING LATE MORNING AND AFTERNOON SEA BREEZES. NRN
LYNN CANAL LOOKS LIKE IT WILL PICK UP TO 20-25 KT IN THE AFTERNOON
SAT AS WELL. OVER THE CENTRAL GULF...WINDS AHEAD OF THE WEAK FRONT
WILL GENERALLY BE AROUND 20 KT...WITH A SLOW DIMINISHING TREND
BEHIND THE FRONT.

TEMPS LOOK TO REBOUND QUITE A BIT SAT WITH MORE SUNSHINE EXPECTED
FOR MOST OF THE AREA. 925 MB TEMPS WARM TO AROUND 13-16C FOR MOST
INNER CHANNEL AREAS...WITH 18-20C FOR THE HYDER AREA. THIS WOULD
ALLOW TEMPS TO REACH THE UPPER 60S TO LOWER 70S OVER THE N AND
CENTRAL AREAS...AND THE MID 70S TO LOWER 80S OVER THE S...WITH
HYDER THE MOST LIKELY SPOT TO REACH THE LOWER 80S. THE OUTER COAST
WILL ALSO BE WARMER SAT BUT ENOUGH ONSHORE FLOW IN LOWER LEVELS
WILL GENERALLY KEEP TEMPS IN THE UPPER 50S TO MID 60S.

.LONG TERM...BUILDING RIDGE OF HIGH PRESSURE MENTIONED ABOVE WILL
BE THE DOMINANT SYNOPTIC WEATHER FEATURE FOR SOUTHEAST ALASKA
THROUGH EARLY TUESDAY. THE RIDGE WILL THEN FLATTEN AND SHIFT TO
THE SOUTHEAST RESULTING IN AN INCREASE IN CLOUDS AND RAIN CHANCES
OVER THE AREA. THE MAIN CHANGE TO THIS FORECAST PACKAGE WAS TO
SPEED UP RAIN CHANCES AND INCREASE CLOUD COVER TO THE SECOND HALF
OF TUESDAY. THIS IS A BIT OF A CHANGE FROM THE PREVIOUS FEW DAYS
WHEN IT WAS THOUGHT THE PATTERN CHANGE WOULD OCCUR MORE TOWARDS
THE LATE WEDNESDAY AND EARLY THURSDAY TIME FRAME.

CLOUDS WILL BE ON THE DECREASE SUNDAY WITH THE WARMEST DAY
OCCURRING ON MONDAY AS MUCH OF THE AREA WILL SEE PARTLY CLOUDY
SKIES. THIS COMBINED WITH 850 MB TEMPERATURES IN THE 15 TO 18C
RANGE WILL RESULT IN WIDESPREAD 70S ACROSS THE AREA. SOME OF THE
INLAND LOCATIONS THAT DO NOT RECEIVE SEA BREEZES WILL LIKELY REACH
THE 80 DEGREE MARK. THE PATTERN BEGINS TO CHANGE ON TUESDAY AS THE
RIDGE FLATTENS AND IS PUSHED TO THE SOUTHEAST. THIS WILL RESULT IN
INCREASED CLOUD COVER AND CHANCE POPS FOR MUCH OF THE REMAINDER OF
THE WEEK. HOWEVER...AT THIS TIME IT DOES NOT APPEAR THERE WILL BE
ANY SIGNIFICANT SYSTEM THAT WILL RESULT IN WIDESPREAD OR HEAVY
RAINFALL THROUGH NEXT THURSDAY. WINDS WILL MAINLY BE DIURNALLY
DRIVEN THROUGH TUESDAY WITH THE NORMAL AFTERNOON SEA BREEZES AND
LIGHTER WINDS AT NIGHT.

CONTINUED WITH A BLEND OF THE NAM/ECMWF FOR UPDATES TO THE
EXTENDED RANGE. FOR DAYS 5 THROUGH 8 UTILIZED THE LATEST WPC
GUIDANCE. FORECASTER CONFIDENCE IS ABOVE AVERAGE IN A GENERAL
TRANSITION TO MORE CLOUDS AND CHANCES OF RAIN BY MID WEEK BUT
DETAILS STILL NEED TO BE FINE TUNED OVER THE COMING DAYS.

&&

.HYDROLOGY...WATCHING MENDENHALL LAKE YET AGAIN AS IT HAS BEEN
RISING STEADILY FOR THE PAST 24 HRS OR SO. COORDINATED WITH RFC
ABOUT THIS...AND THEY SUSPECT IT IS ANOTHER GLACIAL DAMMED LAKE
RELEASE AS THE PRECIP AMOUNTS ACROSS THE AREA WOULD NOT HAVE
JUSTIFIED THE AMOUNT OF RISE THAT HAS OCCURRED. THE LAKE LEVEL WAS
AT 7.4 FEET AS OF 2215Z...AND IS FORECAST TO PEAK NEAR 8 FEET
THIS EVENING THEN DROP RAPIDLY OVERNIGHT TONIGHT AND SAT. THIS IS
SLIGHTLY HIGHER THAN THE RELEASE LAST WEEKEND...BUT STILL BELOW
FLOOD LEVELS BY AROUND 1 FOOT. IT WILL NEED TO BE MONITORED
CLOSELY BY LATER SHIFTS FOR POSSIBLE HYDRO STATEMENT OR SPS
ISSUANCE.

&&

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

&&

$$

RWT/TPS

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.