Area Forecast Discussion - Southeastern
FXAK67 PAJK 011230
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
430 AM AKDT WED OCT 1 2014
.SHORT TERM...CLIPPER LOW THAT TRACKED FROM THE NORTHEAST GULF
SOUTHWARD TUESDAY THROUGH TUESDAY NIGHT HAS WEAKENED TO AN OPEN
WAVE TROUGH THAT IS MOVING OVER THE SOUTHERN PANHANDLE AND INTO
BRITISH COLUMBIA. SCATTERED TO ISOLATED SHOWERS OVER THE SOUTHERN
REGIONS WILL END EARLY THIS MORNING AND AS HIGH PRESSURE THAT IS
BUILDING OVER THE YUKON MOVES SOUTHWARD SKIES WILL BEGIN TO
CLEAR. THIS AREA OF HIGH PRESSURE WILL COVER THE PANHANDLE THROUGH
LATE TONIGHT WITH CLEAR SKIES CONTINUING. THE UPPER LEVEL TROUGH
THAT DROPPED OVER THE REGION LAST NIGHT BROUGHT IN COLD AIR MASS
THAT WILL REMAIN IN PLACE THROUGH THE NIGHT. EXPECT DAY TIME TEMPS
TO RISE INTO THE UPPER 40S TO LOW 50S BUT SOME UNCERTAINTY ON
THIS. THERE IS THE CASE THAT THE COLD AIR MASS WILL KEEP TEMPS LOW
BUT INSOLATION DUE TO THE CLEAR SKIES MAY PROVIDE MORE WARMING. NOT
AS MUCH OF AN ISSUE FOR OVERNIGHT LOWS AS THE COLD AIR MASS ALONG
WITH RADIATIONAL COOLING WILL DROP TEMPS INTO THE MID 20S TO LOW
30S FOR THE NORTHERN AREAS AND MID TO UPPER 30S FOR THE SOUTH.
PATCHY FOG HAS DEVELOPED FOR THE CENTRAL PANHANDLE AS SKIES BEGAN TO
CLEAR THIS MORNING. FOG WILL BURN OFF THIS MORNING AS TEMPERATURES
RISE. WITH THE LINGERING MOISTURE DEVELOPMENT OF BLACK ICE IS
POSSIBLE TONIGHT BUT DRYING TREND THROUGH THE DAY SHOULD LIMIT
THIS OVER THE NORTHERN AREAS.

GRADIENT BETWEEN THE HIGH CURRENTLY OVER THE YUKON AND THE EXITING
LOW PRODUCING SMALL CRAFT WINDS OVER THE NORTHERN LYNN CANAL. THE
GRADIENT WILL WEAKEN TODAY WITH DECREASING WINDS THIS AFTERNOON,
BUT THEN REFORM TONIGHT FROM THE NEXT ADVANCING SYSTEM. A
DEVELOPING LOW WILL MOVE FROM THE NORTH PACIFIC INTO THE WESTERN
AK GULF TONIGHT. WINDS OVER THE OFFSHORE WATERS WILL RISE TO GALE
FORCE FOR THE SOUTHWESTERN AREAS BY LATE TONIGHT. AS THIS LOW
ADVANCES THE PRESSURE GRADIENT BETWEEN THE CANADIAN HIGH WILL BEGIN
TO INCREASE EASTERLY OUTFLOW WINDS. MAIN IMPACT FROM THIS SYSTEM
WILL NOT BE FELT UNTIL THURSDAY. WITH THE CLEAR SKIES TONIGHT AND
LINGERING MOISTURE FROM TODAY THERE IS POSSIBILITY OF FOG
DEVELOPING OVER THE SOUTHERN AREAS BUT THINK THE INCREASING WINDS
WILL LIMIT THIS.

MODELS WERE IN GOOD CONSENSUS FOR THE SYNOPTIC PATTERN.
DIFFERENCES WILL MAINLY WITH DAY TIME TEMPS AND FOG DEVELOPMENT
LATE TONIGHT. PREFERRED A BLEND OF NAM/ECMWF WHICH WAS STILL
IN LINE WITH INHERITED FORECAST, SO FEW CHANGES WERE MADE TO THE
GRIDS. FORECAST CONFIDENCE IS ABOVE AVERAGE.
.LONG TERM...MODELS REMAIN IN GENERAL AGREEMENT FOR A GALE FORCE
LOW ENTERING SOUTH CENTRAL GULF EARLY THURSDAY MORNING WITH
INCREASING CLOUDS AND POPS OVER THE OUTER WATERS...THEN LEADING TO
A POTENTIAL HEAVY RAINFALL DURING THE AFTERNOON INTO THE EVENING
HOURS ACROSS THE SOUTHERN AND CENTRAL PANHANDLE ALONG WITH STRONG
WINDS DEVELOPING OVER THE IMMEDIATE COASTAL SECTIONS THURSDAY
AFTERNOON INTO THE EVENING HOURS. POSTED STRONG WINDS HEADLINES
FOR ZONES 23 AND 27. THE LOW WILL TRACK NORTHWARD TO THE
NORTHEASTERN GULF COAST THROUGH FRIDAY NIGHT. USED THE NAM AND
ECMWF FOR A FEW FINE TUNES OVER THE PRESSURE...WINDS...POPS AND
QPF FIELDS THROUGH SATURDAY NIGHT AS THE LOW CONTINUES TO WEAKEN
OVER THE NORTHERN GULF. HIGH PRESSURE AREA ACROSS THE NORTHWESTERN
CANADA WILL DRIFT EAST AS THE LOW TRACKS NORTHWARD ACROSS THE
GULF...THUS THE NORTHERLY PRESSURE GRADIENT ACROSS THE INNER
CHANNELS WILL DIMINISH AND THE FRONTAL BOUNDARY ASSOCIATED WITH
THE LOW WILL PRODUCE GENERAL SOUTHERLY WINDS BY FRIDAY.

MODEL SPREADS BECOME LARGER SUNDAY INTO EARLY NEXT WEEK WITH AN
UPPER LEVEL SHORTWAVE TROUGH PERSISTING ACROSS THE GULF. MERELY NO
CHANGES WERE MADE FOR THE EXTENDED FORECAST PERIODS AND ADDED DAY
8 WITH THE GFS BASED GUIDANCE. MAINTAINED GENERALLY WET WEATHER
THROUGH EARLY NEXT WEEK WITH DECREASING POPS BY THE MID WEEK.
FORECAST CONFIDENCE REMAINS ABOVE AVERAGE WITH THE FRONTAL PASSAGE
THROUGH LATE FRIDAY THEN FALLS BELOW AVERAGE THROUGH THE WEEKEND
INTO EARLY NEXT WEEK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM THURSDAY AFTERNOON THROUGH THURSDAY EVENING FOR 
     AKZ023-027.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-013. 
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041>043. 

&&

$$

PRB/AHN

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