Area Forecast Discussion - Southeastern


FXAK67 PAJK 222332
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
400 PM AKDT MON SEP 22 2014 
.SHORT TERM...TRANSITION TO A QUIETER WEATHER PATTERN ACROSS
SOUTHEAST ALASKA OVER THE NEXT 24 HOURS. UPPER LEVEL LOW OVER THE
YUKON WILL CONTINUE TO DRIFT NORTHEAST WITH RIDGE OF HIGH PRESSURE
CURRENTLY OVER THE PANHANDLE GETTING PUSHED TO THE NORTH AND EAST
ON TUESDAY. THIS IS IN RESPONSE TO A STRENGTHENING LOW PRESSURE
SYSTEM MOVING INTO THE NORTHEAST PACIFIC AND BECOMING NEARLY
STATIONARY FOR THE NEXT FEW DAYS RESULTING IN A MUCH LESS ACTIVE
WEATHER PATTERN FOR THE PANHANDLE.

THUNDERSTORM THREAT MAINLY OVER THE GULF AND FAR OUTER COAST WILL
DIMINISH EARLY THIS EVENING AS FORCING WEAKENS AND WEAK WARM AIR
ADVECTION FROM THE SOUTH BEGINS TO STABILIZE THE ATMOSPHERE A BIT.
THIS WILL ALSO BE THE CASE WITH SHOWER ACTIVITY OVER THE REMAINDER
OF THE PANHANDLE WITH SHOWERS BECOMING SCATTERED TO ISOLATED BY
LATE TONIGHT. DRIER AIR ALOFT WILL FILTER INTO THE AREA WITH
BREAKS IN THE CLOUD COVER INCREASING OVERNIGHT. WITH SOME BREAKS
IN THE CLOUD COVER, RESIDUAL LOW LEVEL MOISTURE AND LIGHTNING
WINDS HAVE INCLUDED PATCHY FOG ACROSS MUCH OF THE AREA TONIGHT AND
TUESDAY MORNING. SHOWERS WILL HAVE ENDED BY TUESDAY MORNING WITH
DRY CONDITIONS AND DECREASING CLOUDS ACROSS THE NORTHERN
PANHANDLE. EXPECT TO HAVE BANDS OF CLOUDS MOVING BACK INTO THE
SOUTHERN PANHANDLE IN RESPONSE TO THE LOW MOVING INTO THE
NORTHEAST PACIFIC. TEMPERATURES WILL RANGE FROM THE LOW TO UPPER
40S TONIGHT WITH UPPER 50S TO MID 60S TUESDAY AFTERNOON.

20-25 KT OF SOUTHERLY WIND IN NORTHERN LYNN CANAL AND SKAGWAY WILL
WEAKEN EARLY THIS EVENING. OTHERWISE, WINDS WILL BE ON THE LIGHT
SIDE FOR THE SHORT TERM OVER THE AREA. AS THE LOW PRESSURE SYSTEM
MOVES INTO THE NORTHEAST PACIFIC TUESDAY EXPECT WINDS TO SHIFT TO
THE NORTH AND INCREASE TO 10 TO 15 KT IN THE INNER CHANNELS BY THE
AFTERNOON. 

USED THE 12Z NAM FOR UPDATES TO THE FORECAST OVER THE NEXT 24
HOURS. THIS RESULTED IN MINOR CHANGES AND MAINLY LOCAL AREA EDITS.
FORECASTER CONFIDENCE IS ABOVE AVERAGE IN DECREASING SHOWERS AND
CLOUDS THROUGH TUESDAY AFTERNOON.
.LONG TERM...SHOULD HAVE FINALLY TRANSITIONED TO A TEMPORARILY
QUIETER PATTERN AS OF TOMORROW PM. AT THIS TIME REGION BEGINS TO
SEE CLOUD COVER INCREASE OUT AHEAD OF A STACKED LOW PRESSURE SYSTEM
MOVING SLOWLY NORTHWARD FROM WELL SOUTH OF THE PANHANDLE. THIS WILL
AFFECT MAINLY THE SOUTHERN HALF THROUGH ABOUT FRI WHEN IT RAPIDLY
WEAKENS.
DEPENDING ON THE MODEL THE PRECIPITATION REACHES A BIT INTO THE
NORTHERN HALF WITH THE GFS HAVING PRECIP THERE BUT THE OTHER MODELS
CONFINE LIGHT AMOUNTS AT AND SOUTH OF THE HALFWAY POINT. GEMS SEEMS
TO BE OVERDONE ON LOW-LEVEL SPINUP WITH THIS SYSTEM. WE CHOSE A
COMPROMISE WITH INCREASED WINDS MOSTLY OVER THE SOUTH AND A CHANCE
OVER PORTIONS OF THE NORTHERN HALF WITH LIKELY POPS OVER THE FAR
SOUTH. AT THE SAME TIME THE NORTHERN QUARTER GETS BRUSHED BY A
SHORTWAVE IN NW FLOW ALOFT WHICH WILL LIKELY PROVIDE A DEEP DRY
LAYER AND WHERE IT REMAINS CLEAR MINIMUM TEMPS WILL BE MINIMIZED
WED AND THU PM. GFS SHOWS THE RIDGE SHARPER ALSO WIND INCREASES
WILL LIKELY BE FELT OVER NORTHERN LYNN AND YAKUTAT FROM WED MORNING
THROUGH PROBABLY THURSDAY...AND THIS MAY INHIBIT NIGHTLY COOLING
OVER EXPOSE AREAS. 

THEN A NEW UPPER LOW DIGGING SOUTHEAST PAST THE ALEUTIANS IS THE
WEATHERMAKER FROM ABOUT FRIDAY AM ONWARDS. THIS LARGE LOW APPEARS
SIGNIFICANT AT THIS POINT ON MODEL ENSEMBLES AND IS CENTERED OVER
THE CENTRAL GULF BY SAT. SOUTHERLY/SELY WINDS AND RAIN WILL LIKELY
BE AREA-WIDE FOR THE WEEKEND. THE GFS TAKES A DOUBLE-BARRELLED,
STRONGER APPROACH WHILE ECMWF IS A BIT WEAKER ALOFT AND THE GEM
STRONGER. GEM SOLUTION IS FURTHER SOUTH BUT MORE CONSOLIDATED BY
SUNDAY. GFS HAS A VERY STRONG FRONT
OVER THE EASTERN GULF ON SAT WITH SOME SIMILARITIES TO LAST
WEEKENDS SYSTEM. TOO EARLY TO DILENEATE DETAILS...ALTHOUGH MODEL
SPREAD IS NOT THAT LARGE FOR STRENGTH AND THE CONSENSUS IS FOR A
STORMY WEEKEND. WE TOOK THE WPC APPROACH AFTER ABOUT FRIDAY FOR
NOW. FORECAST CONFIDENCE IS ABOUT AVERAGE FOR THIS PERIOD. 

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041>043-051-052. 

&&

$$

TPS/DAW