Weather Service Report


069 
FXAK67 PAJK 041334
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
534 AM AKDT WED MAY 4 2016

.SHORT TERM...A RIDGE OF HIGH PRESSURE SITUATED OVER THE
PANHANDLE WILL SHIFT TO THE SOUTHEAST OVER THE NEXT 24 HOURS. A
WEAK TROUGH LIFTING NORTHEAST OVER THE PANHANDLE THIS MORNING WILL
SHIFT EAST OF THE AREA BY EARLY THIS AFTERNOON. AN AREA OF LOW
PRESSURE MOVING INTO THE NORTH CENTRAL GULF WILL SEND A WEATHER
FRONT INTO THE NORTHERN PANHANDLE LATE TONIGHT. ANOTHER MORE
POTENT WEATHER SYSTEM WILL BE RIGHT ON ITS HEELS FOR THURSDAY.
MORE ON THAT SYSTEM IN THE LONG RANGE SECTION BELOW.

MAIN CHANGES TO THE FORECAST WERE TO INCREASE PRECIPITATION
CHANCES AND WIND SPEEDS OVER THE NORTHERN PANHANDLE TONIGHT.

PERSISTENT ONSHORE FLOW ALONG WITH LIFT FROM THE UPPER LEVEL
TROUGH WILL GENERATE SCATTERED SHOWERS THIS MORNING AND INTO THE
AFTERNOON. SHOWERS WILL BE MOST PREVALENT OVER THE NORTHERN
PANHANDLE. A BRIEF DECREASE IN SHOWER ACTIVITY WILL OCCUR LATE
THIS AFTERNOON AND EARLY THIS EVENING AS THE RIDGE SHARPENS IN
RESPONSE TO THE APPROACHING FRONT. RAIN WILL SPREAD OVER THE
NORTHEAST GULF COAST EARLY THIS EVENING AND INTO THE REMAINDER OF
THE NORTHERN PANHANDLE BY LATE EVENING. PRECIPITATION WILL BE
CONFINED TO ROUGHLY FREDERICK SOUND AND NORTHWARD TONIGHT AS
RIDGING PREVAILS OVER THE SOUTHERN PANHANDLE.

A GENERALLY WEAK WIND REGIME IS PRESENT THIS MORNING OVER THE
PANHANDLE. THE STRONGEST WINDS ARE OVER THE FAR NORTHERN INNER
CHANNELS WITH 15 KT IN LYNN CANAL AND GUSTS TO 20 KT AT THE
SKAGWAY AIRPORT. THIS WILL REMAIN THE CASE THROUGH MUCH OF THE
DAY. THE APPROACH OF THE FRONT TONIGHT WILL LEAD TO AN INCREASE IN
WIND SPEEDS ACROSS THE NORTHERN PANHANDLE. 700 MB SOUTHWESTERLY
FLOW INCREASES TO 30-35 KT BY LATE TONIGHT OVER LYNN CANAL WHICH
WILL SUPPORT SMALL CRAFT WINDS AND CONTINUED GUSTS IN THE SKAGWAY
AREA. FOR THE REST OF THE NORTHERN PANHANDLE, 10-20 MPH CAN BE
EXPECTED ACROSS THE LAND AREAS BY LATE TONIGHT. UNDER THE
INFLUENCE OF HIGH PRESSURE AND A WEAK PRESSURE GRADIENT, WINDS
ACROSS THE SOUTHERN PANHANDLE WILL REMAIN ON THE LIGHTER SIDE.

USED THE 00Z GFS AND THE HIRES ARW/NMM FOR UPDATES TO THE FORECAST
THROUGH THE FIRST 24 HOURS.

.LONG TERM...OCCLUDED FRONT WILL MOVE INTO THE ERN GULF BY THU
AFTERNOON...THEN HANG UP AS A LOW PRESSURE WAVE MOVES NE ALONG IT
THU NIGHT INTO FRI MORNING. THE FRONT SHOULD THEN PUSH SLOWLY
ACROSS THE AREA LATER FRI THRU SAT. THERE MAY END UP BEING ANOTHER
LOW PRESSURE WAVE THAT MOVES ACROSS THE SRN AREA SAT AS WELL...BUT
MODELS DIFFER ON THIS. MAY SEE A QUIETER/DRIER PATTERN DEVELOP
FOR NEXT WEEK WITH MODELS HINTING AT RIDGING OVER THE GULF THAT
MIGHT KEEP SYSTEMS TO THE S AND W OF THE AREA. 

STILL LOOKS LIKE SIGNIFICANT RAINFALL WITH FRONTAL SYSTEM FOR LATE
WEEK ALONG WITH POTENTIALLY STRONG WINDS IN SOME AREAS. INITIALLY
ON THU...INCREASED WARM ADVECTION OVER LEFTOVER FRONT OVER THE
CENTRAL AREA WILL KEEP PRECIP GOING OVER THE N-CENTRAL AREA AT
LEAST. THEN PRECIP BAND WITH MAIN OCCLUDED FRONT WILL SPREAD NE
INTO MUCH OF THE AREA THU AFTERNOON AND EVENING. EXPECT GALE FORCE
WINDS ALONG AND AHEAD OF THE FRONT...WITH STRONGEST WINDS LIKELY
OVER THE N GULF. THE FAR SERN AREA THOUGH WILL BE PROTECTED BY A
STRONG RIDGE BUILDING INTO SRN BC...SO THE PRECIP SHIELD WILL BE
HELD UP MOSTLY TO THE NW OF THAT AREA INTO AT LEAST FRI MORNING.
THE HEAVIEST RAIN SHOULD FALL OVER THE NRN PANHANDLE AND NE GULF
COAST THU AFTERNOON INTO FRI. STILL LOOKS LIKE 2-4 INCHES OR MORE
OF RAIN DURING THAT TIME FRAME. DID INCREASE WINDS SOME FOR THE
INNER CHANNELS WITH THE BIGGEST INCREASE OVER LYNN CANAL AS
MODERATE TO STRONG SWLY FLOW ALOFT WILL ENHANCE LEE TROF IN LOWER
LEVELS NEAR PAGY THU NIGHT INTO FRI NIGHT.

EVENTUALLY THE HEAVIER RAIN WILL SHIFT TOWARD THE SRN PANHANDLE
FRI NIGHT INTO SAT AS FRONT DRIFTS SE INTO THAT AREA AND
POTENTIALLY ANOTHER LOW PRESSURE WAVE MOVES ACROSS THEM. LOOKS
LIKE THE FRONT SHOULD FINALLY BE OUT OF THE AREA BY SAT
EVENING...BUT UPPER TROF WILL MOVE ACROSS AND KEEP SOME THREAT FOR
PRECIP GOING INTO SAT NIGHT AND SUN.

STILL LOOKING LIKE A MUCH NEEDED BREAK IN THE ACTIVE WEATHER
PATTERN FOR NEXT WEEK WITH RIDGE BUILDING OVER AND/OR W OF THE
AREA. MODELS DIFFER ON SHAPE OF THE RIDGE AND WHETHER ANY SYSTEM
MIGHT BE ABLE TO SNEAK THROUGH IT INTO THE AREA FROM EITHER THE S
OR W. STILL PLENTY OF TIME TO ADJUST THIS PART OF THE FORECAST IF
NEEDED.


&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052. 
     SMALL CRAFT ADVISORY FOR PKZ012-043-051. 
&&

$$

TPS/RWT

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