Area Forecast Discussion - Southeastern
FXAK67 PAJK 252320
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
320 PM AKDT MON MAY 25 2015
.SHORT TERM...HIGH PRESSURE RIDGE AT THE SURFACE OVER THE AK GULF
IN THE PROCESS OF REBUILDING AND WILL BECOME THE DOMINATE FEATURE
FOR SE AK. AN UPPER LOW FORMING NEAR KODIAK WILL BEGIN TO TRACK
EASTWARD WITH THE NEGATIVELY TILTED TROUGH NEARING THE PANHANDLE
COAST BY TUESDAY AFTERNOON. A WEAK VORT MAX OVER THE SOUTHERN
PANHANDLE KEPT IN ORE CLOUD COVER, ESPECIALLY NEAR AKZ029 BUT WILL
MOVE OFF THE THE EAST AS THE NEXT SHORT WAVE MOVES IN. SATELLITE
IMAGERY THIS AFTERNOON SHOWING MARINE STRATUS BAND OVER THE AK
GULF WITH CLEARING SKIES OVER THE PANHANDLE. THE MARINE LAYER
MOVED INLAND WITH SOME AREAS OF FOG THIS MORNING. A FEW LOCATIONS
HUNG ONTO THESE LOW CLOUDS INTO THE AFTERNOON BUT AS OF NOW MOST
LOCATIONS ARE UNDER CLEAR OR PARTLY CLOUDY SKIES. AS THE UPPER
LEVEL LOW MOVES IN WILL SEE COMBINATION OF THE MARINER LAYER MOVE
INLAND ALONG WITH HIGHER CLOUDS COVERING MOST OF THE PANHANDLE
THROUGH THE DAY TUESDAY. ANY CHANCE OF PRECIPITATION FROM THIS
SHORT WAVE WILL BE MORE IN THE EXTENDED RANGE WITH JUST SLIGHT
CHANCE TO CHANCE POPS REACHING THE PANHANDLE COAST BY TUESDAY
AFTERNOON, MAINLY NEAR AKZ017. COLDER AIR ALOFT MOVING IN WITH THE
SYSTEM, 850 MB TEMPS CURRENTLY IN THE 4 TO 6 C RANGE WILL DROP
INTO THE -2 TO 2 C RANGE. AIR MASS WILL BE STABLE ENOUGH INITIALLY
FOR RAIN TO BE STRATIFORM.

WINDS OVER THE COASTAL WATERS AND NEAR INNER CHANNEL OCEAN
ENTRANCES HAVE BEEN BIT SLOWER TO PICK UP ON THE LEE SIDE OF THE
BUILDING RIDGE. TONED SOME SPOTS BACK ABOUT 5 KT BUT BY TUESDAY DO
EXPECT THESE WINDS TO PICK UP TO 20 KT WITH SMALL CRAFT NEAR CROSS
SOUND AND POTENTIAL TIP JET NEAR CAPE DECISION. WITH A HEAT LOW
OVER THE YUKON SOUTHERLY PRESSURE GRADIENT BETWEEN THE AK GULF
HIGH WILL BRING UP WINDS OVER NORTHERN LYNN CANAL TO SMALL CRAFT
LEVELS. SEA BREEZE DEVELOPED THIS AFTERNOON AND EVENING WITH THE
CLEARING SKIES AND INCREASED THERMAL GRADIENT. TUESDAY WILL WILL
BE LESS THERMALLY DRIVEN DUE TO INCREASED CLOUD COVER AND MORE
FROM GRADIENT FLOW.

MODELS NOT SHOWING TOO MUCH VARIATION FORM PREVIOUS RUNS. BLENDED
IN GEM WITH INHERITED GRIDS AS IT WAS A NICE MID POINT BETWEEN THE
NAM, WHICH WAS PREFERRED FOR THE FIRST 12 HOURS, THEN THE ECMWF,
WHICH WAS PREFERRED FOR THE NEXT 12 HOURS. MAIN QUESTION WILL BE
EXTENT OF MARINE LAYER MOVING INLAND AN HOW THE UPPER LOW EFFECTS
IT. RESULTING CLOUD COVER WILL HAVE DOMINO EFFECT ON TOMORROWS
HIGH TEMPS AND AND AFTERNOON SEA BREEZE DEVELOPMENT. FORECAST
CONFIDENCE IS AVERAGE.
.LONG TERM...UPPER LOW SHOULD HEAD E INTO THE PANHANDLE TUE NIGHT
AND WED...THEN DRIFT SLOWLY TO THE SE AND OUT OF THE AREA BY LATE
THU NIGHT. UPPER RIDGE WILL TRY TO REESTABLISH CONTROL OVER THE
AREA FOR FRI INTO THE WEEKEND...BUT WILL HAVE TO WATCH FOR
POTENTIAL SHORTWAVE ENERGY DROPPING INTO THE AREA IN A N-NW FLOW
ALOFT. MODEL DIFFERENCES INCREASE EARLY NEXT WEEK...SO NOT A LOT
OF CONFIDENCE IN WHAT WILL HAPPEN THEN. ENDED UP USING A BLEND OF
THE 12Z GEM AND EC FOR TUE NIGHT-THU EVENING...THEN MAINLY WPC FOR
LATE THU NIGHT ONWARD...ALTHOUGH DID BLEND IN SOME EC FOR THU
NIGHT-FRI NIGHT. TEMPS WED WILL LIKELY GET HELD DOWN INTO THE 50S
TO LOWER 60S GIVEN AMOUNT OF CLOUD COVER AND PRECIP POTENTIAL.

LOOKS LIKE INCREASING PRECIP THREAT FOR MAINLY THE NRN AND CENTRAL
AREAS TUE NIGHT AND WED AS UPPER LOW MOVES IN AND ONSHORE LOW
LEVEL FLOW CONTINUES. BUMPED POPS UP SOME...BUT STILL LIMITED THEM
TO CHANCE LEVELS AT MOST FOR TUE NIGHT-WED. LATER SHIFTS MAY NEED
TO BUMP THEM UP FURTHER AS MODELS HONE IN ON EXACT TRACK OF UPPER
LOW AND ATTENDANT SHORTWAVES ROTATING AROUND IT...BUT LOOKING LIKE
BEST PRECIP THREAT WILL BE IN THE PAJN-PAEL CORRIDOR.

FOR WED NIGHT-THU...MODELS SUGGEST SHORTWAVE ENERGY WILL WRAP
AROUND THE UPPER LOW INTO THE AREA WED NIGHT WITH MORE ORGANIZED
PRECIP MOVING IN FROM THE NE. MODELS DIFFER ON WHERE THIS PRECIP
BAND MOVES IN...SO ENDED UP GOING WITH A LARGER AREA OF CHANCE
POPS TO HANDLE THIS OVER THE NRN HALF OF THE PANHANDLE WED NIGHT.
LATER SHIFTS MAY NEED TO BOOST POPS EVEN MORE FOR THIS SYSTEM.
THINK WHATEVER PRECIP DOES COME ACROSS WILL RAPIDLY DIMINISH EARLY
THU AS SHORTWAVE DIVES S AND OUT OF THE AREA. TEMPS THU SHOULD BE
WARMER AS CLOUDS DECREASE ACROSS MUCH OF THE AREA...WITH MOST
PLACES GETTING WELL INTO THE 60S OVER THE INNER CHANNELS.

LOOKING RATHER DRY THU NIGHT INTO AT LEAST SAT...WITH WARMER AIR
MOVING BACK INTO THE AREA AS UPPER RIDGE BUILDS IN. WILL NEED TO
MONITOR MARINE LAYER WITH A FAIRLY STRONG SFC HIGH DEVELOPING OVER
THE GULF...BUT SHARPNESS OF LOW LEVEL RIDGE AXIS MAY KEEP MOST OF
IT OFFSHORE. TEMPS SHOULD REBOUND BACK TO ABOVE AVERAGE LEVELS FOR
THIS TIME FRAME...WITH SOME 70S RETURNING TO THE INNER CHANNELS.

FORECAST CONFIDENCE LOWERS AFTER SAT DUE TO INCREASING DIFFERENCES
AMONGST THE MODELS ON POTENTIAL SHORTWAVE ENERGY DROPPING INTO
THE AREA FROM THE N OR NW. WPC SEEMED LIKE A GOOD COMPROMISE AT
THIS POINT. MAY SEE A BIT MORE CLOUD COVER DEPENDING ON HOW MUCH
SHORTWAVE ENERGY REACHES SE AK. THIS MAY ALSO CAUSE TEMPS TO BE A
BIT COOLER AS WELL. 

&&
.HYDROLOGY...WARMER TEMPERATURES THE PAST DAYS AND INCREASED SNOW
MELT HAVE RAISED RIVER LEVELS TO NEAR BANKFULL, BUT NOT OVER.
RIVERS SHOWING THIS DIURNAL TREND HAVE BEEN THE CHILKAT, TAIYA AND
TATSHENSHINI. WITH ADVANCING UPPER LEVEL LOW, DECREASING SNOW
LEVELS AND INCREASED CLOUD COVER RIVER LEVELS WILL DROP OVER THE
NEXT FEW DAYS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022. 

&&

$$

PRB/RWT

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