FXAK67 PAJK 050010
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
310 PM AKST SAT FEB 4 2012

.SHORT TERM...LOW PRESSURE IN THE NORTH PACIFIC HAS ALLOWED FOR
A SLIGHT OFFSHORE FLOW OVER THE REGION TODAY...LEADING TO MOSTLY
CLEAR SKIES AND DRYING CONDITIONS. AS THE LOW PROGRESSES NORTH
AND HIGH PRESSURE SETTLES OVER THE YUKON AND BC...EXPECT LIGHT
WINDS TO SHIFT TO THE NORTH THROUGH THE INSIDE WATERS...BECOMING
STRONG FOR HAINES AND SKAGWAY LATE TONIGHT WITH MAX GALES IN
NORTHERN LYNN CANAL. OTHER AREAS WILL SEE THE STRONGEST WINDS
THROUGH INSIDE PASSES WITH LIGHTER WINDS IN BETWEEN.

INTERESTING TEMPERATURE SET UP FOR TONIGHT AND TOMORROW. THE LOW
MOVING UP FROM THE SOUTH IS ADVECTING IN WARMER AIR IN THE LOWER
TO MID LEVELS...AROUND 800 TO 3000FT. AT THE SAME TIME CLEAR
SKIES TONIGHT WILL ALLOW FOR GOOD RADIATIONAL COOLING AT THE
SURFACE ALONG WITH SLIGHT COLD AIR ADVECTION WITH THE NORTHERLY
FLOW. WHAT MAKES THIS COMPLICATED IS AREAS WITH GUSTY WINDS WILL
ALLOW FOR THE WARMER AIR TO MIX DOWN...HOWEVER THE CAA MAY
COUNTER THAT. THEREFORE EXPECT COLDEST TEMPERATURES TONIGHT TO BE
IN WIND SHELTERED VALLEY LOCATIONS.

THE MOIST GROUND AND CAPPING TEMPERATURE INVERSION WILL CAUSE
AREAS OF FOG TO DEVELOP LATE TONIGHT AND EARLY SUNDAY. AREAS WITH
A BIT MORE WIND WILL SEE LESS FOG POTENTIAL.

AS THE LOW MOVES INTO THE SE GULF IT WILL WEAKEN TO AN OPEN
TROUGH ALONG THE ASSOC WARM FRONT. EXPECT SELY WINDS TO INCREASE
ALONG THE SOUTHERN COAST WITH THIS FRONT BY SUNDAY AFTERNOON AND
HAVE INCLUDED A STRONG WIND HEADLINE FOR THE HYDABURG AREA.
KETCHIKAN MAY SEE SOME GUSTY WINDS WITH THIS FRONT AS WELL...BUT
BELOW HEADLINE CRITERIA. RAIN WILL REACH THE PANHANDLE LATE
SUNDAY MORNING AND SPREAD NORTH THROUGH THE AFTERNOON. MOST
PRECIP WILL FALL AS RAIN...BUT A FEW AREAS TO THE NORTH THAT STAY
BELOW FREEZING WITH NORTHERLY CAA WITH SEE SOME SNOW FLAKES
MIXING IN.

MODELS DIFFERED ON HOW THE LOW PROGRESSES NORTH. THE NAM12 AND
GFS INITIALIZED WELL AND HAD THE BEST RUN TO RUN CONSISTENCY SO
USED THAT FOR MOST UPDATES. FORECASTER CONFIDENCE IS AVERAGE.

&&

.LONG TERM...AT MID LEVELS A BLOCKING RIDGE OVER THE WESTERN US
AND CANADA REMAINS IN PLACE FOR THE WEEK. 500 MB LOWS OVER HUDSON
BAY AND KAMCHATKA PENINSULA ALSO REMAIN QUASI STATIONARY. A
SERIES OF MID LEVEL TROUGHS WILL ROTATE AROUND THE STATIONARY
KAMCHATKA LOW THROUGH THE WEEK. WEAKENING FRONT WILL MOVE OVER
THE NORTHERN PANHANDLE SUNDAY EVENING AS ASSOCIATED LOW PRESSURE
SYSTEM IN THE AK GULF WEAKENS TO AN OPEN WAVE TROUGH. PRECIP OVER
THE PANHANDLE WILL DIMINISH FROM SOUTH TO NORTH IN THE EVENING.
PRECIP WILL START AS ALL RAIN AND IF THE FRONT REMAINS INTACT
LONG ENOUGH WILL SEE RAIN MIX WITH SNOW AS TEMPERATURES DROP
OVERNIGHT. HOWEVER SINCE THE FRONT IS FAIRLY WEAK NOT EXPECTING
MUCH SNOW ACCUMULATION WITH AMOUNTS LESS THAN 1 INCH. HIGH
PRESSURE OVER NORTHERN BRITISH COLUMBIA WILL REMAIN IN PLACE BUT
AS PRESSURE GRADIENT WEAKENS AS AK GULF DISSIPATES WILL SEE WINDS
BEGIN TO DROP SLIGHTLY OVER THE PANHANDLE. GRADIENT WILL INCREASE
MONDAY AS NEXT LOW PRESSURE SYSTEM MOVES UP FORM THE NORTH
PACIFIC INTO THE SOUTHWESTERN GULF. THE TRACK OF THESE NEXT LOWS
MONDAY INTO TUESDAY REMAIN FAR ENOUGH TO THE WEST LIMITING ANY
PRECIP MOVING OVER OUR AREA. BY WEDNESDAY AN OCCLUDED FRONT
ASSOCIATED WITH A LOW NEAR KODIAK WILL MOVE OVER THE PANHANDLE
ENDING THE BRIEF DRY PERIOD. FAIR AMOUNT OF UNCERTAINTY BY THE
END OF THE WEEK BUT THE NEXT SYSTEM MOVING INTO THE SOUTHEAST
GULF THURSDAY EVENING INTO FRIDAY MAY BE FAIRLY STRONG AND WILL
NEED TO BE MONITORED FOR WIND AND HEAVY PRECIP.

WHILE MODELS WERE IN PRETTY GOOD AGREEMENT WITH THE MID LEVEL
SYNOPTIC SCALE PATTERN MODELS BEGIN TO DIVERGE SIGNIFICANTLY BY
DAY 2 WITH RESPECT TO SURFACE DETAILS. RUN TO RUN CONSISTENCY FOR
THE GFS WAS A BIT BETTER THAN THE ECMWF BUT BOTH ARE SHOWING
LARGE DIFFERENCES BETWEEN OPERATIONAL AND ENSEMBLES FORECASTS.
THE 12Z NAM AND 12Z GFS WERE IN GOOD AGREEMENT FOR THE START OF
THE LONG TERM WITH THE 00Z AND 12Z ECMWF QUICKLY BECOMING AN
OUTLIER. THE 12Z UKMET SEEMED MORE OF A MIDDLE GROUND FOR SUNDAY
EVENING BUT ALSO BECAME AN OUTLIER WHILE THE GFS AND NAM REMAINED
IN LINE. EVEN THOUGH THEY WERE CONSISTENT DIFFERENCE BETWEEN THE
GFS AND NAM EXIST OVER THE NORTHERN PANHANDLE YUKON BORDER.
DECIDED TO BLEND IN SOME 12Z NAM BUT OVER ALL KEPT PRESSURE AND
WINDS GRIDS THE SAME. WIND DIRECTION OVER THE CENTRAL INNER
CHANNELS FOR THE START OF THE WEEK A BIT COMPLICATED. GEOSTROPHIC
FLOW KEEPS THE WINDS SOUTHERLY BUT PRESSURE GRADIENT KEEPS THEM
NORTHERLY. DECIDED TO LEAN MORE TOWARDS THE PRESSURE GRADIENT
SOLUTION. THE NEW HPC GRIDS WERE CHECKED BUT DECIDED TO HOLD OFF
USING IT FOR UPDATES AS IT WAS USING MORE OF THE ECMWF. FORECAST
CONFIDENCE IS LOW DUE TO SUCH LARGE MODEL DIFFERENCES BUT AT
LEAST FOR THE START OF THE LONG TERM THOSE DIFFERENCES ARE MAINLY
WITH SYSTEMS JUST TO THE WEST OF OUR REGION.


.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING FOR
AKZ027.
STRONG WIND FROM 3 AM AKST SUNDAY THROUGH SUNDAY MORNING FOR
AKZ025.
STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH SUNDAY MORNING
FOR AKZ019.
STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH SUNDAY EVENING
FOR AKZ018.
MARINE...GALE WARNING FOR PKZ011>013-022-031-036-041-042.
SMALL CRAFT ADVISORY FOR PKZ021-032>035-043-051-052.

&&

$$

HANNON/PRB




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