Area Forecast Discussion
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FXAK67 PAJK 291352 CCA
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
548 AM AKDT TUE JUL 29 2014

.SHORT TERM...BLOCKING PATTERN REMAINS IN PLACE WITH UPPER
TROUGH POSITIONED OVER THE GULF...WITH A RIDGE EXTENDING
NORTHWARD INTO THE BERING SEA AND A SECOND RIDGE LOCATED OVER
WESTERN CANADA. THE SECOND OF TWO UPPER IMPULSES ROTATING AROUND
THE LARGE SCALE TROUGH WILL MOVE OVER THE AK PANHANDLE THROUGH
THE DAY BRINGING MORE PRECIPITATION TO THE REGION. AS THE 500 MB
VORT MAX TRACKS NORTHWARD WITH MID LEVEL FLOW SHIFTING FROM THE
SOUTHEAST TO SOUTHWEST PRECIPITATION WILL BEGIN TO DIMINISH THIS
EVENING AND OVERNIGHT. STEADIER STRATIFORM RAINFALL SWITCHES TO
MORE CONVECTIVE SHOWER ACTIVITY AS COLD AIR FROM THE SOUTH MOVES
IN ALOFT. PRECIPITABLE WATER VALUES FOR THE DAY STILL AROUND
1 INCH WITH MODERATE RAIN FALL POSSIBLE AT TIMES. SURFACE LOW
OVER HAIDA GWAII CAN BE SEEN ON IR SATELLITE IMAGERY THIS MORNING
MOVING NORTHWARD. THIS LOW WILL WEAKEN THROUGH THE DAY WHILE A
LARGER SURFACE LOW OVER THE EASTERN AK GULF RETROGRADES WESTWARDS
AS A RIDGE OF HIGH PRESSURE BUILDS OVER THE PANHANDLE. WINDS FOR
THE SOUTHERN PANHANDLE WILL DECREASE THROUGH THE MORNING AS THE
SOUTHERLY PUSH FROM THE SURFACE LOW MOVES NORTHWARD. THE CENTRAL
AND NORTHERN REGION WINDS WILL SHIFT TO THE SOUTH THROUGH THE
MORNING WITH INCREASING WINDS SPEEDS AS THE PRESSURE GRADIENT
FROM THE BUILDING HIGH STRENGTHENS. FOR NOW NOT EXPECTING ANY
SMALL CRAFT WINDS TO DEVELOP BUT WILL SEE SUSTAINED WINDS IN THE
15 TO 20 KT RANGE. HOWEVER NORTHERN LYNN CANAL IS CLOSEST TO
HAVING SMALL CRAFT POTENTIAL THIS AFTERNOON AND EVENING. DAYTIME
HIGHS REMAINING IN THE UPPER 50S TO LOW 60S DUE TO PRECIP AND
CLOUD COVER. AS PRECIPITATION DIMINISHES OVERNIGHT TEMPERATURES
SHOULD BE A FEW DEGREES COOLER THAN PREVIOUS NIGHTS, THUS THE
DEVELOPMENT OF FOG LATE TONIGHT.

BIT MORE MODEL SPREAD FOR SURFACE DETAILS DUE TO THE WEAKENING
FEATURES, BUT STILL GOOD CONSENSUS FOR SYNOPTIC PATTERN. KEPT WITH
A BLEND OF 00Z ECMWF/GEM WHICH RESULTED IN ONLY MINOR CHANGES TO
WIND SPEEDS. OTHER FIELDS SEEM TO STILL BE ON TRACK SO LITTLE
CHANGES WERE MADE. FORECAST CONFIDENCE IS AVERAGE.

.LONG TERM...PATTERN CHANGE IN STORE FOR THE EXTENDED FORECAST. THE
LOW IN THE GULF THAT HAS BEEN AFFECTING OUR WEATHER FOR THE LAST
WEEK WILL RETROGRADE SW INTO THE NORTH PACIFIC THROUGH THE SECOND
HALF OF THE WEEK. THIS WILL ALLOW THE NUMEROUS SHOWERS ON WEDNESDAY
TO BECOME MORE SCATTERED AND TAPER OFF FROM SOUTH TO NORTH THROUGH
WEDNESDAY NIGHT. ON THURS WEAK HIGH PRESSURE WILL SETTLE OVER THE
NORTHERN GULF COAST/NORTHERN PANHANDLE AS A THERMAL INVERTED TROUGH
PUSHES INTO THE SOUTHERN PANHANDLE. THIS WILL CAUSE A WEAK NORTHERLY
FLOW THROUGH THE INSIDE WATERS AND FAIR WEATHER INTO SATURDAY.
MODELS HAVE COME INTO BETTER AGREEMENT ON THESE COUPLE DAYS OF DRY
WEATHER AND THE NORTHERLY FLOW SHOULD EVEN ALLOW FOR MORE SUNSHINE.
HAVE WARMED HIGH TEMPERATURES SLIGHTLY BUT MAY NEED TO BE WARMED
EVEN MORE IF IT IS SUNNY...THE SOUTHERN PANHANDLE LOOKS TO BE THE
MOST LIKELY TO SEE HIGHS IN THE LOWER 70S. WEAK NORTHERLY FLOW WILL
CAUSE SEA BREEZES TO DEVELOP IN THE AFTERNOONS WHICH WOULD DAMPER
THOSE HIGHS SLIGHTLY. STRONGEST SEA BREEZES WOULD BE IN PLACES THAT
ALREADY HAVE A NWLY SEA BREEZE LIKE KETCHIKAN, WRANGELL AND SITKA.

SATURDAY NIGHT INTO SUNDAY MODELS START TO HAVE MORE SPREAD. THE
ECMWF BRINGS RAIN BACK TO THE REGION OVER THE WEEKEND WHILE THE
GFS KEEPS US DRY UNTIL THE START OF NEXT WEEK. BLENDING THESE TWO
SOLUTIONS RESULTED IN A CHANCE OF RAIN OVER THE SECOND HALF OF THE
WEEKEND AND LESS CONFIDENCE IN THAT PART OF THE FORECAST.
OTHERWISE MODELS WERE IN GOOD AGREEMENT AND FORECAST CONFIDENCE IS
AVERAGE.

&&

.AVIATION...VARIABLE CEILINGS AND VISIBILITIES THIS MORNING FROM
THE SHORTWAVES MOVING OVER THE REGION WILL EVENTUALLY BECOME MORE
STABLE WITH IMPROVING CONDITIONS THROUGH THE DAY AND OVERNIGHT.
FOG DEVELOPMENT LATE TONIGHT COULD BE SIGNIFICANT IF CLOUD COVER
DISSIPATES MORE RAPIDLY RESULTING IN INCREASED RADIATIONAL
COOLING AND MORE FOG DEVELOPING.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.


$$

PRB/FERRIN









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