721
FXAK67 PAJK 170026
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
326 PM AKST MON DEC 16 2024
SHORT TERM.../MONDAY NIGHT THROUGH WEDNESDAY/
AN UPPER LEVEL
HIGH/RIDGE LIES OVER THE GULF OF ALASKA WITH WEAK JET MAXES TO
SOUTH OF THE ALEUTIANS AND ANOTHER OVER THE YUKON AND NORTHERN
B.C. THE RIDGE IS ALLOWING IN CLOUDS FROM THE WEST ACROSS THE
NORTHERN 2/3 OF THE PANHANDLE AND EXPECT THAT TO CONTINUE TONIGHT
AS THE RIDGE IS PUSHED NE ACROSS THE REGION BY AN INCOMING TROUGH.
AT THE SURFACE, HIGH PRESSURE LIES IN THE NORTHWEST TERRITORIES
WHILE LOW PRESSURE IS SOUTH OF THE ALEUTIANS. THIS IS CAUSING
GENERAL NORTHERLY FLOW THROUGH THE NORTHERN INNER CHANNELS, BUT
NOT AS STRONG AS WE TYPICALLY SEE WHEN THE HIGH IS IN THE YUKON
AND THE LOW IS IN THE CENTRAL/EASTERN GULF. THIS WILL CHANGE ON
TUESDAY AS A LOW CENTER DEVELOPS UNDER THE UPPER LEVEL TROUGH AND
TRACKS NORTHWARD TO THE SOUTHERN SE GULF. THIS LOW TRACK IS A BIG
CHANGE TO THE FORECAST AS MODELS HAVE BEEN STRUGGLING WITH WHERE
TO TAKE IT, BUT ARE STARTING TO CONVERGE ON THE IDEA OF THE LOW
TURNING ENE THROUGH DIXON ENTRANCE WEDNESDAY MORNING WHILE
STARTING TO DISSIPATE.
CHANGES TO THE FORECAST BASED ON THIS NEW LOW PRESSURE TRACK
INCLUDE:
*REMOVING CHANCE OF PRECIPITATION ACROSS THE NORTHERN
HALF OF THE REGION AND INCREASING IT FOR THE SOUTHERN HALF.
*CONTINUING SNOW ACROSS THE SOUTH FOR WEDNESDAY, LEADING TO A
WINTER WEATHER ADVISORY.
*LOWERING SKY COVER AHEAD OF THE LOW PRESSURE SYSTEM DUE TO
OFFSHORE FLOW.
*LOWERING TEMPERATURES AND SNOW LEVELS, INCLUDING A WARMING TREND
ACROSS THE SOUTH FOR WEDNESDAY NIGHT, USING THE GFS.
FOR THE SOUTHERN PANHANDLE WINTER WEATHER ADVISORY, EXPECT
GREATEST SNOWFALL TO OCCUR ON THE EASTERN SLOPES OF PRINCE OF
WALES ISLAND, ACROSS KETCHIKAN, AND UPPER ELEVATION AREAS ON
ANNETTE ISLAND WITH A RANGE OF 3-7 INCHES EXPECTED OVER A 24 HOUR
PERIOD. WESTERN POW SHOULD SEE A CHANGE TO RAIN FIRST AND THEREFORE
HAVE LESS THAN 2 INCHES OF SNOWFALL FORECASTED. THERE IS POTENTIAL
FOR PERIODS OF FREEZING RAIN BEFORE TEMPERATURES WARM UP...IF THAT
OCCURS THEN STORM TOTAL SNOW WILL BE LOWER BUT IMPACTS MAY BE
GREATER.
THE UPPER LEVEL PATTERN QUICKLY PUSHES OUT THE TROUGH AND SURFACE LOW
PRESSURE BY A BUILDING RIDGE OVER THE EASTERN GULF WEDNESDAY
AFTERNOON. THIS WILL CAUSE WINDS TO TREND DOWN AND PRECIP RATES TO
DROP OFF ACROSS THE SOUTH.
LONG TERM.../THURSDAY THROUGH SATURDAY NIGHT/
MAIN STORY FOR THE
MID AND LONG RANGE FORECAST PERIOD REMAINS AN ACTIVE PATTERN DRIVEN
BY A LARGE SCALE LOW ENTRENCHED OVER THE NORTH PACIFIC, BERING SEA,
AND WESTERN GULF OF ALASKA BY MIDWEEK. MULTIPLE SMALLER CIRCULATIONS
WILL BE SPINNING ABOUT THIS LARGE SCALE FEATURE THROUGHOUT THE
WEEK. AFTER THE FIRST FIRST SYSTEM IMPACTS THE PANHANDLE IN THE
SHORT RANGE, ANOTHER FRONTAL BAND FEATURING GALE FORCE WINDS WILL
PUSH NORTHWARD AND APPROACH THE PANHANDLE LATE WEDNESDAY INTO
THURSDAY. THE SOUTHERN PANHANDLE WILL HAVE LIKELY CHANGED TO ALL
RAIN BY THE TIME OF THIS FRONTAL BAND BRINGING A FRESH INFLUX OF
MOISTURE, THOUGH SOME MIXED PRECIPITATION ISN'T OUT OF THE
QUESTION RIGHT AT ONSET OR DURING ANY HEAVIER SHOWERS. WITH COLDER
AIR STILL IN PLACE OVER THE CENTRAL AND NORTHERN PANHANDLE, AND
PERSISTENT NORTHERLY OUTFLOW, SOME ACCUMULATING SNOW IS EXPECTED
FROM WRANGELL NORTHWARD, WITH 24 HR TOTALS RANGING FROM 1 - 3
INCHES. AS OF THIS FORECAST ISSUANCE, THE CENTRAL PANHANDLE UP TO
FREDERICK SOUND IS EXPECTED TO SEE A TRANSITION TO PRIMARILY RAIN
BY LATE THURSDAY NIGHT, WITH ANY PRECIPITATION REACHING FURTHER
NORTH STILL FALLING AS EITHER A SNOW/RAIN MIX OR ALL SNOW.
DEPENDING ON THE INNER CHANNEL WINDS AND MOMENTUM OF THIS FRONTAL
FEATURE, OVERRUNNING COULD OCCUR WHICH MAY LEAD TO HIGHER SNOW
TOTALS AND A SLOWER TRANSITION TO MIX OR RAIN SNOW FOR THE CENTRAL
PANHANDLE.
WITH HIGHER PRESSURE OVER THE INTERIOR AND A MERRY GO ROUND OF
SYSTEMS MAKING THEIR WAY THROUGH THE GULF, INNER CHANNEL WINDS
WILL REMAIN RATHER STOUT THROUGH THE MID RANGE PERIOD. THE GULF
WILL ALSO BE TURBULENT WITH SEAS OF 20+ FT DUE TO AN ONGOING SSE
SWELL AND THE WINDS ASSOCIATED WITH EACH SYSTEM ROTATING THROUGH.
THIS ACTIVE WEATHER WILL CONTINUE THROUGH THE WEEKEND AND INTO
NEXT WEEK, SO NO REST FOR THE WEARY.
AVIATION
INITIALLY, WE ARE NOTING STRONGER WINDS GOING FOR
SKAGWAY STILL, AND GIVEN POSITION OF THE RIDGE OVER THE YUKON WE
EXPECT THE MODERATE OUTFLOW TO CONTINUE THERE INTO TOMORROW.
OTHERWISE, VFR EXPECTED FOR THE NEXT 24 HOURS ACROSS MOST OF SEAK
AS WEAK RIDGING ACROSS THE REGION IS KEEPING MOST OF ANYTHING
EXCEPT A MID/HIGH DECK STREAMING OVER IN THE NWLY FLOW ALOFT OVER
THE TOP OF THE RIDGE. THE EXCEPTION HERE IS THAT WE STILL HAVE
SOME RESIDUAL MOISTURE AROUND PAJN AND THERE WE EXPECT SOME IFR
CIGS DURING THE EARLY MORNING, BUT IT SHOULD ERODE BY 19Z. WE DO
INCREASE WINDS IN THE SOUTHERN AREAS A BIT AS WELL STARTING
TOMORROW AS THE LOW OVER THE EASTERN GULFAK STARTS IT TREK EWD
PASSING THROUGH DIXON ENTRANCE LATE TUESDAY INTO WEDNESDAY.
MARINE
MODELS FELL MORE IN LINE OVER THE SHORT RANGE RESULTING IN
A FORECAST SHIFT FOR THE FIRST ADVANCING LOW. THIS GALE FORCE SYSTEM
FOR TUESDAY NOW TRACKS FURTHER TO THE EAST CENTERING OVER THE SE AK
GULF THEN MOVING OVER THE DIXON ENTRANCE REGION WEDNESDAY. GALES
OVER THE COASTAL WATERS WINDS WILL NOW BE SITUATED MORE LOCALLY
AROUND THE LOW. HIGHER SEAS FROM SW SWELL AROUND THE LOW ALSO KEEP
MORE TO THE SOUTHERN HALF OF THE AREA. OUTFLOW WINDS WILL LAST INTO
WEDNESDAY BUT WITH THE CANADIAN HIGH LOCATED MORE TO THE NE GRADIENT
WILL SUPPORT GALES FOR THE NORTHERN INNER CHANNELS BUT UNLIKELY
HIGHER. FULLY DEVELOPED SEAS FORM THE LONG WITH FETCH LYNN CANAL
SOUTHWARD KEPT FOR THIS TIME FRAME. AFTER A BRIEF LULL NEXT MAX GALE
FORCE FRONT CROSSES INTO THE EASTERN GULF WEDNESDAY NIGHT INTO
THURSDAY. WILL SEE A SHIFT FROM NORTHERLY FLOW TO SOUTHERLY FOR THE
SOUTHERN HALF OF THE PANHANDLE.
AJK WATCHES/WARNINGS/ADVISORIES
PUBLIC...STRONG WIND FROM TUESDAY MORNING THROUGH TUESDAY AFTERNOON FOR
AKZ318.
WINTER WEATHER ADVISORY FROM 6 PM TUESDAY TO 6 PM AKST WEDNESDAY
FOR AKZ328-330-332.
MARINE...GALE WARNING FOR PKZ012-013-641-661-662.
SMALL CRAFT ADVISORY FOR PKZ021-022-031>036-053-642>644-651-652-
663-664-671-672.
SHORT TERM...FERRIN
LONG TERM....STJ
AVIATION...JG
MARINE...PRB
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