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000
FXAK67 PAJK 241300
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
500 AM AKDT FRI OCT 24 2014

.SHORT TERM...SATELLITE IMAGERY THIS MORNING SHOWING A QUASI
STATIONARY 999 MB LOW OFF THE COAST OF HAIDA GWAII WITH A WEAK
TROUGH OF LOW PRESSURE EXTENDING FROM THE LOW NORTHWESTWARD OVER THE
AK GULF. THIS LOW WILL SHIFT SLIGHTLY TO THE NORTH AND WEAKEN INTO
THE EVENING.

WEAK FRONT/BAND OF PRECIPITATION FROM THIS LOW THAT MOVED OVER THE
PANHANDLE YESTERDAY AFTERNOON AND EVENING IS CURRENTLY EXITING TO
THE NORTH. CLEAR BREAKS BEHIND THIS SYSTEM OVER THE CENTRAL
PANHANDLE RESULTED IN SOME COOLING AND FOG FORMATION. ONE QUARTER
MILE DENSE FOG DEVELOPED OVER THE JUNEAU AIRPORT AND VALLEY WITH
GUSTAVUS AND HOONAH FOG ONLY DROPPING VISIBILITY DOWN TO ONE HALF
MILE OCCASIONALLY. A SECOND FRONT / PRECIPITATION BAND IS NOW
MOVING OVER THE SOUTHERN PANHANDLE AND WILL THEN TRACK NORTHWARD
THROUGH THE DAY AND INTO THE EVENING. THERE IS THUNDER STORM
ACTIVITY OVER THE SOUTHEASTERN QUADRANT OF THE LOW WHICH SHOULD
STAY SOUTH OF OUR MARINE AREA BUT HAVE INCLUDED SLIGHT CHANGE OF
T-STORMS IN CASE SOME CELLS PUSH FURTHER NORTH. THINK THIS SECOND
BAND WILL REMAIN INTACT AS THE PREVIOUS DAYS FRONT DID, THEN DISSIPATE
AS IT PULLS TO THE WEST LATE TONIGHT. RAIN SHOWERS FROM THIS FRONT
WILL NOT PRODUCE MUCH IN THE WAY OF QPF AND MAY AT TIMES FEEL MORE
LIKE LIGHT DRIZZLE. PRECIP AND CLOUD BREAKS BEHIND THE FRONT OVER
THE SOUTHERN PANHANDLE WILL BEGIN LATE TONIGHT WITH PATCHY FOG
DEVELOPING.

WINDS OVER THE SOUTHERN COASTAL AND INSIDE WATERS WILL INCREASE TO
MIN SMALL CRAFT LEVELS AS THE SURFACE LOW MOVES NORTH. SINCE THE
LOW WILL NOT MOVE VERY FAR EXPECTING THESE AREAS OF SMALL CRAFT
WINDS TO REMAIN SOUTH OF FREDERICK SOUND. WINDS PICK UP TO 20 KTS
OVER THE CENTRAL INNER CHANNELS WITH SOME HIGHER EASTERLY GUSTS
FROM CHANNELED TERRAIN AND GAPS DUE TO THE PRESSURE GRADIENT
BETWEEN THE GULF LOW AND WESTERN CANADIAN HIGH PRESSURE. WITH
CLOUD COVER AND RAINFALL DAY TIME HIGHS ONLY EXPECTED TO REACH THE
MID 40S TO LOW 50S. WHILE CLOUD COVER WILL LAST LONGER TONIGHT
THERE IS SOME COOLER AIR ALOFT MOVING IN BEHIND THE LOW WITH
OVERNIGHT TEMPS IN THE UPPER 30S TO LOW 40S.

MODELS STILL SHOWING MORE SPREAD THAN ONE WOULD LIKE TO SEE THIS
EARLY IN THE FORECAST. 00Z ECMWF/GEM HAD GOOD INITIALIZATION WITH
SURFACE PRESSURE FIELD AND WERE USED TO REFRESH INHERITED GRIDS.
CHANGES TO PRESS AND WINDS WERE MINOR. DID LIKE THE NAM/GEM/SREF
POP FIELDS WHICH SHOWED POPS BAND SIMILAR TO THE PREVIOUS DAY SO
POPS ARE NOW BIT HIGHER THIS AFTERNOON AND TONIGHT OVER THE
CENTRAL PANHANDLE. WHILE MODEL AGREEMENT IS NOT GREAT FORECAST
CONFIDENCE IS AVERAGE SINCE EXPECTING A SIMILAR PATTERN TO
YESTERDAYS.

.LONG TERM...MODEL PERFORMANCE HAS BEEN IMPROVED FROM THE
PREVIOUS RUN AND PROVIDES BETTER PREDICTABLE SOLUTIONS THROUGH THE
WEEKEND FOR THE NEAR STATIONARY LOW WEST OF HAIDA GWAII SATURDAY
WEAKENS AND STARTS DRIFTING SOUTHWARD THROUGH SUNDAY. A BROAD WEAK
SURFACE TROUGH WILL EXTEND NORTH FROM THE WEAKENING LOW TO THE
NORTHERN GULF. AN UPPER LEVEL SHORTWAVE TROUGH OVER THE EASTERN
GULF SATURDAY MORNING WILL DRIFT EASTWARD ACROSS THE PANHANDLE TO
THE WESTERN CANADA BY SUNDAY MORNING...FOLLOWED BY A WEAK UPPER
TROUGH MOVES OVER THE PANHANDLE THROUGH MONDAY. AN AMPLIFIED UPPER
RIDGE WILL MOVE EAST ACROSS THE GULF AND THE NORTHERN PANHANDLE
THROUGH THE MID WEEK AS A CLOSED UPPER LOW DIGGING SOUTH FROM
WESTERN ALASKA INTO THE CENTRAL GULF. ANOTHER UPPER RIDGE WILL
BUILD OVER THE BERING SEA AND DRIFT EAST ACROSS THE GULF THROUGH
THE SECOND HALF OF NEXT WEEK. REFRESHED THE INHERITED FORECAST
PACKAGE WITH THE ECMWF THROUGH LATE SUNDAY EVENING THEN USED THE
WPC ENSEMBLE SOLUTIONS FOR THE REMAINING LONG TERM PERIODS.
FORECAST CONFIDENCE ABOUT AVERAGE THROUGH THE WEEKEND THEN FALLS
BELOW AVERAGE FOR THE NEXT WEEK AS MODEL SOLUTIONS DIFFER ON THE
TROPICAL STORM ANA MOVING INTO THE SOUTHERN GULF.

INCREASING OFFSHORE FLOW WILL CONTINUE TO PUSH SHOWERS
DIMINISHING ACROSS THE PANHANDLE THROUGH SUNDAY MORNING...BUT
ANOTHER WEAK UPPER TROUGH MOVING OVER THE PANHANDLE WILL BRING
CHANCE POPS BACK TO THE AREA SUNDAY AFTERNOON INTO THE EVENING
HOURS. MODELS CONTINUE DIVERTING FOR NEXT WEEK AS THEY HANDLE THE
TROPICAL STORM ANA...CURRENTLY RECURVING NORTHEASTWARD OVER
NORTHWEST OF HAWAII. THE LATEST CENTRAL PACIFIC HURRICANE CENTER
PREDICTION MAINTAINS ANA ABOUT THE SAME TROPICAL STORM STRENGTH
THROUGH SUNDAY NIGHT AS IT REACHES NEAR 47N/143W...HEADING TOWARD
HAIDA GWAII THROUGH MONDAY EVENING. THE WPC ENSEMBLE SOLUTION
KEEPS ANA JUST SOUTHWEST OF HAIDA GWAII BY EARLY TUESDAY
MORNING...KEEPING WET WEATHER ACROSS THE SOUTHERN PANHANDLE LATE
MONDAY NIGHT THROUGH WEDNESDAY. THE AMPLIFIED UPPER RIDGE MOVING
EAST ACROSS THE GULF AND THE NORTHERN PANHANDLE WILL KEEP
GENERALLY DRY WEATHER ACROSS THE NORTHERN PANHANDLE UNDER OFFSHORE
LOW TO MID LEVEL FLOW AND ALSO BRING COLD AIR ADVECTION THROUGH
THE MID WEEK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...DENSE FOG ADVISORY UNTIL 9 AM AKDT THIS MORNING FOR AKZ025.
MARINE...SMALL CRAFT ADVISORY FOR PKZ033-035-036-041.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ042.

&&

$$

PRB/AHN

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