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593
FXAK67 PAJK 221350
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
550 AM AKDT FRI MAY 22 2015

.SHORT TERM...UPPER LOW JUST S OF HYDER WILL DRIFT SLOWLY SWD THRU
TONIGHT. A SERIES OF SHORTWAVES ROTATING AROUND THE UPPER LOW WILL
MOVE ACROSS SE AK THRU TONIGHT. UPPER RIDGE WILL SLOWLY BUILD OVER
THE ERN GULF AND YUKON THRU TONIGHT. INVERTED TROF EXTENDS NW FROM
SRN BC INTO THE SRN PANHANDLE...AND WILL REMAIN THERE BUT WEAKEN
SOME STARTING TONIGHT. HIGH PRESSURE WILL REMAIN OVER THE ERN GULF
THROUGH TONIGHT. GENERALLY PREFERRED THE 06Z NAM AND 00Z ECMWF FOR
THE SHORT RANGE AS THEY SEEMED TO HAVE BEST HANDLE ON THE
SHORTWAVES ROTATING AROUND THE UPPER LOW.

MAIN FORECAST CONCERNS WILL BE TSTM POTENTIAL...MARINE LAYER...AND
WINDS. THINK ANY TSTMS THAT DEVELOP WILL BE TIED TO SHORTWAVES
MOVING INTO THE AREA FROM THE E. LOOKS LIKE A WARMER DAY IN
GENERAL ESPECIALLY FOR THE INNER CHANNELS DUE TO A MORE OFFSHORE
FLOW IN LOWER LEVELS. ELONGATE VORT MAXIMA IS CROSSING THRU SE AK
THIS MORNING...BUT WILL ONLY GENERATE PATCHY MID-LEVEL CLOUDS.
LOOKS LIKE A PAIR OF SHORTWAVES WILL APPROACH THE AREA THIS
AFTERNOON AND EVENING. THE MORE SRN SHORTWAVE SHOULD REACH THE
SRN AREA LATE IN THE DAY...WHILE THE MORE NRN SHORTWAVE APPROACHES
THE N-CENTRAL AREA LATE IN THE DAY. BOTH SHOULD TRIGGER CONVECTION
GIVEN 400+ J/KG CAPES...BUT THE SRN AREA WILL BE MORE UNSTABLE IT
APPEARS. HAVE LOW POPS FOR SHOWERS AND TSTMS FOR THE ERN INNER
CHANNELS THIS AFTERNOON AND EVENING TO COVER THESE SHORTWAVES.
THEN...A LARGER SHORTWAVE LOOKS LIKE IT WILL REACH THE FAR SERN
PANHANDLE LATE TONIGHT WITH MORE ORGANIZED SHOWER ACTIVITY. CANNOT
RULE OUT A RUMBLE OF THUNDER WITH THIS SYSTEM AS WELL...BUT FOR
NOW ONLY WENT WITH SHOWERS FOR THE LATE NIGHT HOURS THERE AS TEMPS
ALOFT ACTUALLY WARM A BIT AS SHORTWAVE COMES IN.

MARINE LAYER CONTINUES TO BLANKET THE ERN GULF AND FOR THE MOST
PART THE OUTER COAST. IT IS NOT AS EXPANSIVE OVER THE SRN COAST E
OF THE OUTERMOST ISLANDS THOUGH...ALTHOUGH PATCHY STRATUS DID
DEVELOP NEAR THE HIGHER TERRAIN. THINK THE MARINE LAYER WILL BURN
OFF MOST OF THE OUTER COAST TODAY...WITH LEAST CHANCE OF THAT
AROUND THE PAEL AREA. THINK THE LOW CLOUDS WILL PUSH BACK ONTO THE
COAST TONIGHT. SOME LOW CLOUDS AND FOG ALSO MOVED INTO THE FAR
SERN INNER CHANNELS EARLY THIS MORNING. FLOW IS IN PROCESS OF
TURNING MORE NWLY THOUGH AS INVERTED TROF SLOWLY INTENSIFIES
THERE...SO THE LOW CLOUDS SHOULD PUSH OUT EARLY IN THE MORNING.
DO NOT THINK THEY WILL RETURN TONIGHT GIVEN FORECASTED NWLY LOW
LEVEL FLOW THERE. OTHER CLOUDS WILL BE THERE THOUGH DUE TO
SHORTWAVES MOVING IN TONIGHT.

AS FOR WINDS...THEY WILL GENERALLY BE NWLY OVER THE AREA WITH HIGH
OFFSHORE AND TROF INLAND. LOCAL EFFECTS MAY TEMPORARILY OFFSET THIS
FLOW DURING THE AFTERNOON...BUT THE NWLY FLOW SHOULD BECOME
DOMINANT AGAIN IN THE EVENING. MAY SEE SCA LEVEL WINDS OVER THE
FAR ERN GULF S OF CROSS SOUND THIS AFTERNOON AND EARLY EVENING.
REST OF THE AREA SHOULD REMAIN BELOW SCA LEVELS...BUT ANY
CONVECTION THAT FLARES UP COULD CAUSE LOCALLY GUSTY WINDS TO SCA
LEVELS NEARBY.

OTHERWISE...TEMPS LOOK TO BE A FEW DEGREES WARMER TODAY DUE TO THE
MORE OFFSHORE FLOW. MANY AREAS OVER THE INNER CHANNELS SHOULD GET
INTO THE 70S...WITH A FEW SPOTS POSSIBLY REACHING 80 OVER THE NRN
AREA. CLOUDS MOVING IN TONIGHT WILL KEEP TEMPS A BIT MILDER
TONIGHT THAN THEY WERE EARLY THIS MORNING IN MANY AREAS. NOT
EXPECTING ANY RH VALUES BELOW 30 PERCENT TODAY...BUT IF SOME OF
THE NELY FLOW CAN MIX DOWN TO THE SFC...THERE COULD BE SPOTTY
BELOW 30 RH VALUES. EVEN SO...FIRE DANGER WILL REMAIN ELEVATED DUE
TO VERY DRY CONDITIONS. AREA RIVERS AND STREAMS THAT ARE FED BY
SNOWMELT FROM THE SURROUNDING MTNS OVER THE NRN AREA WILL SEE A
BIT MORE RUNOFF TODAY SO THEY WILL LIKELY RISE SOME...BUT NONE OF
THEM ARE EXPECTED TO THREATEN FLOOD LEVELS ATTM.

.LONG TERM...LOW LEVEL RIDGE OFFSHORE APPEARS LIKELY TO WEAKEN BY LATE
WEEKEND AS WEAK FRONT MAKES ITS WAY ACROSS THE NORTHERN PANHANDLE
ASSOCIATED WITH AN INFLUX OF ENERGY ALOFT OFF THE EAST END OF THE
DEEP ALEUTIAN TROUGH. ONLY WEATHER ASSOCIATED WITH THE FRONT IS
LIKELY TO BE A TEMPORARY INCREASE IN CLOUD COVER OVER THE NORTHERN
PANHANDLE AND SHOWERS IN THE FAR-OFFSHORE AND YAKUTAT AREAS LATE SUN
AND MONDAY. THEN THE RIDGE BUILDS ALOFT AGAIN EARLY NEXT WEEK AND
THE LOW LEVEL OFFSHORE RIDGE REBUILDS. 70S SHOULD BE COMMON ON
FRI/SAT ACROSS THE PANHANDLE AWAY FROM THE DIURNAL COASTAL
INFLUENCE...BUT APPEARS THAT SUNDAY AND MONDAY WILL MOSTLY BE IN
THE 60S. DIURNAL PUSH OF STRATUS WILL LIKELY CONTINUE FOR FAVORED
COASTAL ZONES SAT AND SUN...BUT LIKELY A BIT WEAKER ON SUN AS
RIDGE WEAKENS. USED THE NEW EC/NAM RUNS FOR MINOR UPDATES IN THE
GRIDS FOR THE FRI-MON PERIOD WITH MOS TEMPERATURES. WITH WARMING
TEMPS ALOFT THE DIURNAL, ISOLATED THUNDERSTORM ACTIVITY WILL
CONTINUE TO BE MINIMAL OVER THE CENTRAL AND NORTHERN PANHANDLE
THIS WEEKEND. PORTIONS OF THE SOUTHERN HALF OF THE PANHANDLE AND
OVER ELEVATED TERRAIN ON THE EASTERN SIDE ON FRI WILL LIKELY SEE
SOME SCATTERED STORM DEVELOPMENT. FOR SAT THE ONLY FAVORABLE AREA
FOR CONVECTION APPEARS LIKELY TO BE THE HYDER AREA WHERE COLDER
TEMPS ALOFT WILL REMAIN...REMAINDER OF ACTIVITY SHOULD BE WELL
EAST IN BC.

MODELS ARE CONSISTENT IN MAINTAINING THE UPPER RIDGE...ASIDE FROM
THE MONDAY BRUSHBACK OVER THE NORTH...THROUGH MIDWEEK AND LIKELY
THROUGH THE WEEK. THOUGH THE GEM HINTS AT A SUBTROPICAL PUSH OF
MOISTURE ABOUT MIDWEEK...ALL 3 OF THE MODELS MAINTAIN THE LONGWAVE
DEEP TROUGH POSITION OVER THE ALEUTIANS AND GENERAL RIDGING OVER
THE PANHANDLE THROUGH 1 WEEK OF SIMULATION. THIS WAS CONSISTENT
WITH EARLIER RUNS AND THE 12Z WPC GUIDANCE UTILIZED 00Z EC AND 06Z
GEM RUNS. THUS MUCH OF DAYS 5-8 IN THE GRIDS WERE NOT CHANGED. SHOULD BE
NOTED THAT DETAILS UNDER THE UPPER RIDGE ARE SOMEWHAT CONVOLUTED
AT TIMES IN THE TUE-FRI TIMEFRAME WITH MINOR MODEL DIFFERENCES...
SO CLOUD COVER AND CONVECTION AT TIMES CANNOT BE RULED OUT. ALSO
SUBTROPICAL MOISTURE SHOULD BE MONITORED AS TIME GOES ON AS IT
WILL NO DOUBT BECOME A FACTOR AS LOW LEVELS CONTINUE TO WARM UP
AND WILL ONLY REQUIRE A WEAK WAVE TO TRIGGER ORGANIZED CONVECTION
AT SOME POINT. WITH RIVERS CURRENTLY ELEVATED FROM SNOWMELT THE
SENSITIVITY TO MOISTURE PLUMES AND CONVECTION WILL INCREASE. AT
THIS POINT HOWEVER IT STILL APPEARS THAT ANY SIGNIFICANT FRONTAL
ACTIVITY WILL LIKELY BE DELAYED OVER THE EASTERN GULF AND
PANHANDLE UNTIL AT LEAST LATE NEXT WEEK.

CROSS SOUND (DIURNALLY) AS WELL AS THE SOUTHERN ADJACENT OFFSHORE MARINE
ZONES WILL SEE SCA-LEVEL WINDS OR NEAR-SCA ON FRI AND SAT. AS THE
RIDGE OFFSHORE TEMPORARILY WEAKENS ON SUN THE WINDS WILL WEAKEN IN
THESE AREAS...BUT WILL LIKELY RETURN TO SCA LEVEL EARLY NEXT WEEK.

MODEL CONFIDENCE IS ABOVE AVERAGE THROUGH THE EXTENDED PERIOD.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ041>043.

&&

$$

RWT/WESLEY

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