Area Forecast Discussion
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FXAK67 PAJK 021304
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
504 AM AKDT THU JUL 2 2015

.SHORT TERM...THE GALE FORCE LOW IN THE AK GULF THAT HAS BEEN
TRACKING NORTHEASTWARD WILL BEGIN TO WEAKEN THROUGH THE MORNING AS
IT NEAR CAPE FAIRWEATHER.  THE LOW WILL THEN MOVE INLAND THIS
AFTERNOON WEAKENING TO AN OPEN WAVE TROUGH. THIS TROUGH WILL TRACK
TOWARD BRITISH COLUMBIA THIS EVENING WHILE BEGINNING TO DISSIPATE.
MEANWHILE AN AREA OF HIGH PRESSURE WILL BEGIN TO BUILD OVER THE AK
GULF THIS AFTERNOON AND START OF MOVE OVER THE PANHANDLE LATE
TONIGHT AND MERGE WITH THE WEAK RIDGE THAT IS JUST ALONG THE
PANHANDLE BRITISH COLUMBIA BORDER. THIS COMBINED RIDGE WILL EXTEND
NORTHWARD WITH TIGHTENING GRADIENT OVER THE NORTHERN PANHANDLE.

THE FIRST WARP AROUND THE LOW PRODUCED MODERATE RAINFALL OVER THE
CENTRAL AND NORTHERN PANHANDLE AT TIMES WITH LIGHTER PRECIPITATION
OVER THE SOUTHERN PANHANDLE. AS COLDER UNSTABLE AIR BEHIND THE LOW
MOVES IN THE RAIN WILL TRANSITION TO SHOWERS THEN DIMINISH FROM
WEST TO EAST TODAY THROUGH TONIGHT. A CONVECTIVE CELL IN THE
NORTHWEST QUADRANT OF THE GULF LOW PRODUCED A FEW LIGHTNING
STRIKES EARLY THURSDAY MORNING BEFORE IT STARTED TO SHEAR APART.
MODELS STILL SHOWING INCREASED CONVECTIVE PARAMETERS ON THE EAST
SIDE OF THE LOW THIS MORNING AND AFTERNOON, BUT AS OF NOW NO
STRIKES HAVE BEEN DETECTED THERE. KEEPING WORDING OF THUNDERSTORMS
AS JUST SLIGHT CHANCE THROUGH THE DAY AND DID BACK OFF ON THE
EASTWARD EXTENT OF THESE OVERLAND T-STORMS.

GALE FORCE WINDS PICKED UP OVER THE COASTAL WATERS WEDNESDAY
NIGHT AND HAVE MOVED INTO CROSS SOUND. THESE WINDS WILL DROP OVER
QUICKLY THROUGH THE MORNING AS THE LOW WEAKENS AND MOVES INLAND.
SURFACE WINDS PICK UP OVERNIGHT AS 850 MB WINDS IN THE 30 TO 40 KT
RANGE IN ADVANCE OF THE LOW CENTER PUSHED OVERLAND. WHILE THERE
WERE OCCASIONAL GUST OF 35 MPH DID NOT HAVE PROLONGED STRONG
WINDS. WINDS WILL DROP OFF THROUGH THE DAY FOR MOST LOCATION
EXPECT THE NORTHERN PANHANDLE. AS THE HIGH PRESSURE RIDGE BUILDS
THE GRADIENT BETWEEN IT AND THE LOW MOVING INLAND WILL PRODUCE
GALES OVER NORTHERN LYNN CANAL AND STRONG WINDS FOR SKAGWAY.

SOME SLIGHT TIMING ISSUES ON THE MODELS WITH THE LOW POSITION EARLY
THIS MORNING AND HOW QUICKLY IT WILL BECOME AN OPEN WAVE TROUGH.
HOWEVER THIS DIFFERENCES WERE MAINLY ONLY 3 HOURS. DID LIKE A
GFS/ECMWF BLEND AS THE NAM STILL SEEMED A BIT FAST AND FURTHER
EAST WITH THE LOW CENTER. INHERITED PRESSURE GRIDS MATCHED A BLEND
OF NEW MODEL RUNS SO WERE LEFT MOSTLY AS IS. WINDS HAD SOME LOCAL
CHANGES, SUCH AS BUMPING UP WINDS IN HAINES A BIT. FOR POP MODELS
MAY BE HOLDING ONTO SHOWERS ACTIVITY TOO LONG BUT AS AIR MASS IS
BECOMING MORE CONVECTIVE BREAKS IN BETWEEN SHOWERS ARE EXPECTED.
FORECAST CONFIDENCE IS ABOVE AVERAGE.

.LONG TERM...MODELS REMAIN IN GENERAL AGREEMENT THROUGH THE
WEEKEND FOR AN UPPER LOW OVER THE NORTHERN CANADA MOVES FARTHER
EAST AS AN UPPER RIDGE BUILDS ACROSS THE GULF AND PANHANDLE.
SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE GULF AND
PANHANDLE THROUGH SATURDAY NIGHT WITH AN INVERTED TROUGH OF LOW
PRESSURE DEVELOPS OVER VANCOUVER ISLAND. THE INVERTED TROUGH WILL
EXTEND TO THE SOUTHERN PANHANDLE ON SUNDAY. REFRESHED THE
INHERITED FORECAST THROUGH LATE SATURDAY EVENING WITH THE NAM AND
ECMWF FOR THEIR GOOD CONSENSUS. AS HIGH PRESSURE CONTINUES
BUILDING...SOUTHERLY PRESSURE GRADIENT WILL GRADUALLY RELAX BUT
SMALL CRAFT LEVEL WINDS WILL REMAIN OVER NORTHERN LYNN CANAL
THROUGH SATURDAY. ISOLATED TO SCATTERED SHOWERS ACROSS THE
NORTHERN HALF OF THE PANHANDLE FRIDAY MORNING WILL CONTINUE TO
DIMINISH DURING THE AFTERNOON FOLLOWED BY GENERALLY DRY WEATHER
THROUGH THE WEEKEND ACROSS SOUTHEAST ALASKA. .

THE UPPER LEVEL RIDGE WILL WEAKEN AS AN UPPER LOW NEAR ALASKA
PENINSULA PUSHES A TROUGH EAST INTO THE WESTERN AND CENTRAL GULF
THROUGH MID WEEK...THEN THE TROUGH FINALLY MOVES OVER THE CENTRAL
AND EASTERN GULF...THEN POSSIBLY TO THE NORTHERN PANHANDLE BY
THURSDAY WITH A HIGH LEVEL OF UNCERTAINTY. MODEL DIFFERENCES
BECOME LARGER AND USED THE WPC ENSEMBLE GUIDANCE FOR NEXT WEEK TO
DRAW PREDICTABLE FEATURES FOR THE NORTHERN GULF COAST. GENERALLY
DRY WEATHER WILL CONTINUE THROUGH THE WEEK WITH NO SIGNIFICANT
WINDS. WARMING TREND WILL BEGIN ON SATURDAY AND CONTINUE THROUGH
MUCH OF NEXT WEEK. DAYTIME HIGHS WILL BE MOSTLY IN THE 70S WITH
OVERNIGHT TEMPERATURES IN THE 50S.

&&

.HYDROLOGY...WATER LEVELS ON THE TAKU RIVER ARE CONTINUING TO RISE
THIS MORNING FROM THE GLACIAL DAM RELEASE OF LAKE NO LAKE. WATER
TEMPERATURES HAVE STARTED TO LEVEL OUT WHICH MAY INDICATE THE
GLACIAL DAM RELEASED IS NEAR ENDING AND THE RIVER CLOSE TO
CRESTING. AT 5 AM THE TAKU RIVER WAS AT 41.5 FEET AND IS EXPECTED
TO CREST AT 42.8 FEET AT ABOUT 10 AM. MINOR FLOOD STAGE FOR THE
TAKU RIVER IS 43.0 FEET WITH BANKFULL LEVEL CONDITIONS AT 42.0
FEET. THERE IS STILL UNCERTAINTY REGARDING THE AMOUNT OF WATER
THAT WILL BE RELEASED INTO THE TAKU RIVER SO THE CREST HEIGHT AND
TIMING MAY DIFFER FROM THE FORECAST. ELSEWHERE RIVERS HAVE SHOWN
SLIGHT INCREASED DUE TO THE RAINFALL OVERNIGHT BUT NONE ARE
EXPECTED TO REACH BANKFULL.

A SPECIAL WEATHER STATEMENT HAS BEEN ISSUED ON THIS EVENT AND
CONTAINS MORE DETAIL.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 1 PM AKDT THIS AFTERNOON THROUGH LATE TONIGHT
     FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012-043.
         SMALL CRAFT ADVISORY FOR PKZ013-021-022-031>035-042-051-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041.

&&

$$

PRB/AHN

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