Area Forecast Discussion
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FXAK67 PAJK 161404
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
604 AM AKDT TUE SEP 16 2014

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE PANHANDLE
UNDER CLOUDY SKIES WITH A WEAK WEATHER FRONT OVER THE NORTHERN
HALF OF THE AREA. THERE ARE SOME STRONGER SHOWERS NEAR CAPE
SUCKLING THAT ARE PRODUCING SOME ISOLATED THUNDERSTORMS THIS
MORNING. THESE THUNDERSTORMS WILL NOT LAST LONG AS THE UPPER LEVEL
ENERGY WILL BE DRIFT NORTH AND INTO THE EASTERN INTERIOR OF THE
STATE. WINDS ACROSS THE FORECAST AREA THIS MORNING ARE ON THE
LIGHT SIDE AND WITH THAT ALONG WITH THE RAIN AND MOIST CONDITIONS
THERE ARE AREAS OF FOG OVER THE INNER CHANNELS.

THERE IS SOME JET DYNAMICS THAT IS HELPING TO PRODUCE CATEGORICAL
RAIN OVER THE NORTHERN HALF THIS MORNING BUT THE FRONT WILL
CONTINUE TO WEAKEN THROUGH TODAY AS IT SLIDES SE. SO WITH THAT
SAID THE RAIN WILL SLOWLY DIMINISH BY THE AFTERNOON BUT THE
CENTRAL AND SOUTHERN AREAS WILL SEE A CHANCE OF RAIN IN THE LATE
AFTERNOON INTO TONIGHT AS THE FRONT SLIDES SE.

WINDS WILL REMAIN ON THE LIGHT SIDE WITH NOT MUCH OF A PRESSURE
GRADIENT OVER THE FORECAST AREA WITH THE BROAD AREA HIGH PRESSURE.
THIS HIGH PRESSURE WILL DRIFT TO THE EAST AND OVER THE SE AK
TONIGHT AS A WEATHER FRONT CURRENTLY SOUTH OF THE CHAIN DRIFTS
INTO THE WEST CENTRAL GULF BY TONIGHT. THIS FRONT WILL INCREASE
THE WINDS OVER THE CENTRAL GULF TO 15 KT.

FOG WILL RETURN ACROSS THE AREA AGAIN TONIGHT WITH STABLE
CONDITIONS...LIGHT WINDS AND MOIST BOUNDARY LAYER.

OVERALL THERE IS ABOUT AVERAGE FORECAST CONFIDENCE AND USED A
BLEND OF THE GFS/NAM/EC FOR THE FIRST 24HRS MAINLY FOR THE POP
FIELD. BESIDES THAT THERE WAS NOT MANY CHANGES DONE TO THE SHORT
TERM FORECAST.

.LONG TERM...FORECAST PERIOD WILL LIKELY START WITH SOME MORNING FOG WED IN SOME
OF THE INNER CHANNELS...MAINLY SOUTH SIDE. AT THE SAME TIME STRONG
FRONT AND CYCLONE WILL BE ENTERING THE WESTERN GULF AIDED BY
STRENGTHENING JET ON THE SOUTH SIDE. GENERALLY MODELS ARE A BIT
FASTER AND STRONGER WITH THE WINDS AND RAIN IMPACTING THE PANHANDLE
WITH THE SYSTEM WITH SMALL CRAFT ADVISORIES STARTING FROM THE WEST
SIDE ON WED AFTERNOON. GALE WINDS EXPECTED BY THURSDAY MORNING ON
THE OUTER WATERS WITH SIMILAR TIMING OF STARTUP OF SMALL CRAFT
ADVISORIES IN SOME OF THE INNER MARINE ZONES. MODELS ARE SHOWING
ESE FLOW AT 850 MB UP TO 50-60 KNOTS WITH 45-50 KNOTS OVER
PORTIONS OF THE PANHANDLE THURSDAY NIGHT. THUS WE MAY HAVE BEEN
TOO CONSERVATIVE WITH WINDS IN PORTIONS OF THE INNER CHANNELS AND
THIS SHOULD BE MONITORED. THIS WILL CLEARLY BE A MAJOR HAZARD FOR
THE MARINE AREAS AND THE DETAILS WILL EVOLVE WITH TIME. WE SPED UP
THE RAIN ONSET IN THE GULF A BIT PER NAM AND ECWMF FORECASTS ON
THURSDAY AND BUMPED UP THE WINDS IN A FEW LOCATIONS...OTHERWISE NO
SIGNIFICANT CHANGES AS MODELS GENERALLY APPEAR TO HAVE A GOOD
HANDLE ON THINGS THROUGH LATE FRI AND SAT. OVERALL THE EFS AND EC
SHOWED A MORE CONSOLIDATED GULF UPPER LOW FOR THURS-FRI WITH THE
EC WINNING OUT. HOWEVER THE EC SURFACE PRESSURE FIELDS WERE THE
OUTLIER. MAJOR MARINE SWELL EXPECTED BY THURSDAY EVENING EXPANDING
TO ALL OFFSHORE ZONES BY 15Z FRI.

AFTER FRIDAY....DETAILS ON THE MODELS BEGIN TO DIVERGE ON THE
VARIOUS WAVES AND FRONTS WITHIN THE SHARP UPPER TROUGH OVER THE
GULF. BY NEXT MONDAY SIGNIFICANT DIFFERENCES ARE EVIDENT ON THE
LONG RANGE MODELS TO THE POINT THAT PREDICTING SURFACE FEATURES
BECOMES FUTILE...WE LEANED HEAVILY ON WPC AND ENSEMBLE GUIDANCE
FOR THIS PORTION OF THE FORECAST. POSITION OF THE MAJOR LONGWAVE
TROUGH BEGINS TO SHOW MODEL DISCREPANCY BY THIS TIME WITH TIMING OF THE
TROUGH IMPACTS VARIES WIDELY BY MODEL. FORECAST CONFIDENCE OVERALL
IS ABOVE AVERAGE THROUGH ABOUT FRIDAY EVENING THEN DROPS OFF TO
AVERAGE OR BELOW BY NEXT WEEK.


&&

.AVIATION...IFR CONDITIONS WILL CONTINUE TO AFFECT AREA AIRPORTS
THROUGH THE MORNING HOURS. LIFR CONDITIONS WILL BE MAINLY OVER THE
SOUTHERN HALF OF THE AREA. THE FOG AND LOW CLOUDS WILL SLOWLY LIFT
THROUGH THE MORNING HOURS BUT THEY WILL RETURN ACROSS THE INNER
CHANNELS TUESDAY NIGHT TO IMPACT AVIATION TRAVEL WEDNESDAY MORNING.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...DENSE FOG ADVISORY UNTIL 10 AM AKDT THIS MORNING FOR AKZ022-023-
     026-028.
MARINE...SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042.

&&

$$

ABJ/WESLEY

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