Area Forecast Discussion
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000
FXAK67 PAJK 311420
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
620 AM AKDT MON AUG 31 2015

.SHORT TERM...AN UPPER LEVEL LOW CURRENTLY OVER THE YUKON WILL
SHIFT SOUTH THROUGH THE SHORT TERM PERIOD. A STRONG NORTHERLY JET
ON THE WEST SIDE OF THIS LOW IS BRINGING IN COOL ARCTIC AIR TO THE
GULF (WHITEHORSE HAS HAD A MIX OF RAIN/SNOW OVERNIGHT) WHICH HAS
BEEN ENHANCING CONVECTION THE LAST COUPLE DAYS. AT THE SURFACE LOW
PRESSURE OVER THE NE GULF WILL REDEVELOP AND SLOWLY MOVE SE WITH
THE UPPER LEVEL FLOW TO BE OFF HAIDA GWAII BY TUESDAY MORNING.

SHOWERS WILL BE NUMEROUS TODAY THEN DIMINISH FROM NORTH TO SOUTH
AS FLOW TURNS OFFSHORE BEHIND THE LOW. EXPECT SHOWERS TO BECOME
SCATTERED THIS AFTERNOON OVER THE NORTHERN INNER CHANNELS THEN END
IN THAT AREA OVERNIGHT. THE FAR SOUTHERN AREAS WILL SEE SHOWERS
CONTINUING THROUGH THE EVENING WITH THE GREATEST AMOUNTS ON WEST
FACING SLOPES DURING THE DAY. ISOLATED LIGHTNING STRIKES HAVE BEEN
DETECTED OVERNIGHT WITH THE MOST RECENT ONE BEING EAST OF
REVILLAGIGEDO CHANNEL. A SLIGHT CHANCE OF THUNDER REMAINS IN THE
FORECAST THROUGH TONIGHT OVER MOST OF THE OUTSIDE WATERS AND THE
SOUTHERN ZONES.

WINDS WILL SHIFT FROM SELY TO NE-NWLY ONCE THE LOW PASSES WITH
SEVERAL LOCATIONS SEEING SMALL CRAFT LEVEL SPEEDS. STRONGEST WEST
WINDS WILL BE SOUTH OF THE LOW OVER THE OFFSHORE/OUTSIDE WATERS
AND INTO THE OCEAN ENTRANCES NEAR CAPE DECISION THIS MORNING.
STRONGEST S-SELY WINDS WILL BE IN CLARENCE STRAIT ALL DAY. N-NELY
OUTFLOW WINDS WILL INCREASE TONIGHT WITH SMALL CRAFTS EXPECTED OUT
OF CROSS SOUND, NORTHERN LYNN CANAL AND OUT OF INTERIOR PASSES
SUCH AS DISENCHANTMENT BAY.

USED A BLEND OF THE ECMWF AND GEM FOR UPDATES TO PRESSURE TODAY
WITH OTHER ADJUSTMENTS MADE TO WINDS WITH HIRES MODELS FOR LOCAL
EFFECTS SUCH AS OUTFLOW WINDS. FORECAST CONFIDENCE IS ABOVE NORMAL
ON THE DIMINISHING TREND OF THE SHOWERS BUT LOWER ON THE
THUNDERSTORM POTENTIAL.

.LONG TERM...UPPER TROF WILL BE JUST E OF THE AREA FOR MIDWEEK. A
COUPLE OF SHORTWAVES WILL MOVE S INTO THE AREA HOWEVER FOR TUE-
WED. WEAKENING UPPER RIDGE SHOULD MOVE IN FOR THU-FRI TIME
FRAME...THEN ITS LOOKING MORE LIKELY THAT A SYSTEM WILL MOVE INTO
THE AREA FOR THE WEEKEND. USED THE 00Z ECMWF IN A BLEND WITH
PREVIOUS FORECAST FOR TUE-WED...THEN BLENDED IN WPC WITH PREVIOUS
FORECAST FOR REMAINING TIME FRAME...EXCEPT FOR POPS WHICH WERE
LEFT AS IS FROM WED NIGHT ONWARD.

AREA WILL BE UNDER NLY FLOW ALOFT FOR TUE-WED...WHICH GENERALLY IS
A DRIER FLOW PATTERN. HOWEVER...SHORTWAVE ENERGY MOVING THRU THE
AREA MAY KEEP SOME SHOWERS AROUND OVER THE SRN PANHANDLE. THE
STRONGEST SHORTWAVE WILL DROP INTO THE SRN AREA WED. AREAS FURTHER
N WILL SEE DECENT AMOUNT OF CLEARING ESPECIALLY THE CENTRAL
PANHANDLE. WHILE SOME MID AND HIGH LEVEL CLOUDS WILL MOVE ACROSS
THAT AREA...THINK ENOUGH BREAKS WILL OCCUR TO CALL IT PARTLY
CLOUDY FOR THE CENTRAL PANHANDLE. NUDGED MAX TEMPS UP A BIT TUE
WITH MORE SUNSHINE EXPECTED...AND LOWERED SOME MIN TEMPS TUE NIGHT
DUE TO LESS CLOUD COVER. WINDS WILL BE STRONGEST OVER THE NRN HALF
OF THE INNER CHANNELS WITH SFC TROF OVER THE FAR SRN AREA AND HIGH
PRESSURE RIDGE NOSING INTO THE SRN YUKON. SCA LEVEL NLY WINDS ARE
EXPECTED FOR LYNN CANAL AND MAY GET INTO SOME OF THE CENTRAL INNER
CHANNELS AS WELL. LONG DURATION NLY WINDS IN LYNN CANAL WILL ALLOW
SEAS TO BUILD UP BEYOND THE STANDARD 5 TO 1 WIND TO SEA
RATIO FOR THE INSIDE AREAS TUE-WED.

LATER ON...WITH MODELS SLOWLY COMING INTO BETTER AGREEMENT ON
SYSTEM FOR NEXT WEEKEND...IT IS LOOKING MORE LIKELY THAT RAIN
WILL OCCUR THEN. HOWEVER...WOULD LIKE TO SEE THEM GET CLOSER ON
TIMING OF SYSTEM BEFORE RAISING POPS UPWARD. LEFT IN THE CHANCE
POPS SAT-SUN FOR THIS FORECAST PACKAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-033-035-036-041>043-053.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051-052.

&&

$$

FERRIN/RWT

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