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FXAK67 PAJK 271357
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
557 AM AKDT MON APR 27 2015

.SHORT TERM...A VERTICALLY STACKED LOW OVER THE SOUTH CENTRAL GULF
WILL PERSIST THROUGH THE SHORT TERM FORECAST PERIOD WHILE SLOWLY
WEAKENING. AN AREA OF ENHANCED CONVECTION HAS ROTATED AROUND TO
THE NORTHEAST QUADRANT OF THE LOW AND LIGHTNING HAD BEEN DETECTED
OVERNIGHT IN COASTAL MARINE MARINE ZONES 41, 42, 43 AND 51.
LIGHTNING ACTIVITY HAS DIMINISHED IN THE EARLY MORNING HOURS AND
MODELS ARE INDICATING THAT AREAS MOST FAVORABLE FOR CONVECTIVE
ACTIVITY WILL REMAIN OFFSHORE, ROTATING ABOUT THE LOW TO THE
NORTHWEST, AND THEN WEST. THUS, THUNDERSTORMS HAVE NOT BEEN
INCLUDED IN THE ZONE 17 FORECAST THIS MORNING. SHOWERS REMAIN OVER
THE PANHANDLE TODAY AS THE LOW CONTINUES TO SPIN OFF BANDS OF
CONVECTION. FARTHER SOUTH, A LOW HAS FORMED ON THE FRONTAL
BOUNDARY WEST OF THE CALIFORNIA/OREGON BORDER. THIS LOW WILL MAKE
RAPID PROGRESS TO THE NORTH WHILE CONTINUING TO INTENSIFY AND
APPROACH THE DIXON ENTRANCE LATE TONIGHT. AHEAD OF THE LOW,
SHOWERS WILL TRANSFORM TO RAIN AS THE ATMOSPHERE STABILIZES AND
THE ASSOCIATED FRONT MOVES NORTH.

WINDS OVER THE GULF FROM THE FIRST LOW CONTINUE GENERALLY AT HIGH
END SMALL CRAFT INTENSITY OVER THE LOCAL FORECAST DOMAIN, ALTHOUGH ONE
SHIP OBSERVATION IN THE SOUTHEAST QUADRANT REPORTED A SOUTHWEST
WIND OF 35 KTS. SEA STATE OVER THE GULF RANGING FROM 9 TO 14 FEET
WITH 10 TO 11 SECOND SWELL PERIODS. AS THE SECOND LOW INTENSIFIES
AND TRACKS NORTH, WINDS OVER THE SOUTHEAST GULF WILL BACK TO THE
EAST, AND THEN NORTH. STRONGEST WINDS BY LATE TONIGHT SHOULD BE IN
THE DIXON ENTRANCE AND HECATE STRAIT...APPROACHING 40 KTS. WINDS
OVER ZONE 41 AND CLARENCE STRAIT EXPECTED TO REACH 30 KTS, SO NO
GALE WARNINGS ISSUED WITH THE MORNING FORECAST. ALSO HAVE SMALL
CRAFT ADVISORIES OUT FOR SUMNER AND SOUTHERN CHATHAM STRAIT. FARTHER
NORTH, WINDS OVER THE FAR NORTHERN INNER CHANNELS WILL RESPOND TO
THE STRONG NORTHERLY GRADIENT THAT WILL BE CREATED BY THE SECOND
LOW AND REACH SMALL CRAFT INTENSITY OVER LYNN CANAL BY LATE
TONIGHT.

USED A BLEND OF THE 00Z ECMWF AND THE 06Z NAM FOR PRESSURE AD
WIND BASED ON EXCELLENT MODEL AGREEMENT. POP AND QPF A BLEND OF
GFS AND NAM. OVERALL FORECAST CONFIDENCE IS AVERAGE.

.LONG TERM...LOOKS LIKE LOW WILL TRACK ALONG OR JUST A BIT
OFFSHORE THE OUTER COAST TUE WHILE WEAKENING. SOME MODELS SUGGEST
LOW COULD CUT INLAND NEAR CAPE DECISION AND HEAD NWD THRU THE
INNER CHANNELS. THINK PRESENCE OF OLD PARENT LOW OVER THE CENTRAL
GULF WILL HELP STEER THE LOW MORE TO THE NW AS IT ENTERS THE GULF.
AFTER THIS LOW REFORMS INLAND OVER THE SW YUKON TUE NIGHT...WILL
SEE REMAINS OF PARENT LOW DRIFT ACROSS THE ERN GULF AND INTO SE AK
WED. LOOKS LIKE ANOTHER SYSTEM WILL COME INTO THE GULF WED...BUT
APPEARS TO BE FAIRLY WEAK AT THIS POINT. ENDED UP USING A BLEND OF
THE 06Z NAM AND 00Z ECMWF FOR TUE-TUE NIGHT...BUT INCORPORATED
MORE OF THE ECMWF TO KEEP LOW TRACK MORE OFFSHORE.

FOR TUE AND TUE NIGHT...RAIN WILL MOVE NWD ACROSS THE MAIN PART OF
THE PANHANDLE AS LOW MOVES NWD. AFTER LOW PASSES BY...PRECIP WILL
TRANSITION TO SHOWERS ONCE AGAIN. MAY SEE A FEW TSTMS OVER THE FAR
SE GULF AND FAR SRN INNER CHANNELS TUE AFTERNOON. GALE FORCE WINDS
WILL OCCUR ESPECIALLY ON THE S AND E SIDE OF THE LOW...AND MAINLY
OVER THE SE GULF AND SRN INNER CHANNELS. AS LOW CONTINUES FURTHER
N...WINDS WILL FLIP FROM NLY TO SLY AND PICK UP TO SCA LEVELS OVER
THE NRN AREAS LATE TUE AFTERNOON AND EVENING. IT IS POSSIBLE THAT
SOME LAND AREAS MAY NEED STRONG WIND HEADLINES TUE...MAINLY OVER
THE S. THE PAYA AREA WILL LIKELY STAY DRY TUE ALTHOUGH A THREAT
FOR RAIN MAY GET THERE TOWARD THE EVENING.

FOR WED...AS OLD LOW MOVES ONSHORE...WILL CONTINUE TO SEE SHOWERS
OVER THE AREA WITH MOST OF THEM OVER THE SE HALF OF THE AREA.
THINKING THAT SYSTEM WILL WEAKEN ENOUGH TO DIMINISH THREAT FOR ANY
TSTMS BY THIS TIME.

AFTER WED...FORECAST CONFIDENCE DROPS AS MODEL DIFFERENCES
INCREASE. FLOW ALOFT WILL TEND TOWARD A MORE ZONAL CONFIGURATION
WITH SEVERAL SHORTWAVES TRAVERSING EWD IN THIS FLOW. THESE WILL AT
LEAST MAINTAIN A THREAT FOR SOME RAIN OR SHOWER ACTIVITY INTO LATE
WEEK.

&&

.AVIATION...THREAT OF THUNDERSTORM ACTIVITY LIMITED TO THE
IMMEDIATE OUTER COAST, ALTHOUGH CONVECTIVE BUILD UPS AND GUSTY
WINDS IN HEAVIER SHOWERS WILL EXTEND WELL INLAND. NO LLWS, BUT
THIS WILL BE A FACTOR FOR THE SOUTHERN PANHANDLE BY EARLY TUESDAY
MORNING.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-013-022-033-035-036-041>043-051-
     052.

&&

$$

FRITSCH/RWT

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