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000
FXAK67 PAJK 031351
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
551 AM AKDT MON AUG 3 2015

.SHORT TERM...EARLY MORNING WV IMAGERY SHOWS AN UPPER LOW CENTERED
ROUGHLY OVER THE FAR SERN CORNER OF THE PANHANDLE. ELSEWHERE...A
COMPACT UPPER IMPULSE IS PRESENT S OF HAIDA GWAII...AND IS
FORECAST TO ROTATE AROUND THE ERN PERIPHERY OF THE UPPER LOW BY
EVENING...AND THEN WRAP WWD TOWARD HYDER OVERNIGHT. IN THE
MEANTIME...ADDITIONAL MINOR LOBES OF ASCENT WILL PINWHEEL AROUND
THE LOW THROUGH AFTERNOON...ONE OF WHICH IS CURRENTLY YIELDING A
BAND OF COLDER CLOUD TOPS AND ASSOCIATED SHOWERS SPREADING SW FROM
NWRN BC TOWARD PETERSBURG/WRANGELL. THESE SHOWERS ARE EXPECTED TO
BE ORIENTED N-S OVER THE SRN INNER CHANNEL REGION LATER TODAY.
HOWEVER...GREATEST SHOWER COVERAGE WILL BE LOCATED NEAR
HYDER...CLOSER TO THE UPPER LOW CENTER...PARTICULARLY TONIGHT AS
SHOWERS INCREASE INTO THE NUMEROUS CATEGORY AS PREVIOUSLY
MENTIONED UPPER IMPULSE WRAPS WWD TOWARD THE SERN PANHANDLE.

FARTHER N...LOW TO MIDLEVEL N-NELY FLOW WILL BECOME AN
INCREASINGLY DOMINANT FACTOR IN THE SENSIBLE WEATHER OBSERVED OVER
THE NRN HALF OF THE PANHANDLE THIS AFTERNOON AND TONIGHT. HIGH
PRESSURE PERSISTING OVER THE YUKON COMBINED WITH GRADUALLY
DEEPENING LOW PRESSURE OVER THE SRN PANHANDLE WILL FAVOR
INTENSIFYING DOWNSLOPE WINDS FROM YAKUTAT E TO HAINES/SKAGWAY AND
S TO JUNEAU AND GUSTAVUS. THE ATMOSPHERE WILL DRY IN RESPONSE
WITH MIDLEVEL CLOUDS DISSIPATING...AND WHEN COUPLED WITH ADIABATIC
WARMING...TEMPERATURES ARE FORECAST T0 WARM INTO THE 70S DURING
THE AFTERNOON.

BESIDES TEMPERATURES...WEAK MOUNTAIN WAVE DEVELOPMENT WILL BE
POSSIBLE LATE TONIGHT OVER DOWNTOWN JUNEAU AND DOUGLAS DUE TO
INCREASING CROSS BARRIER FLOW. AS A RESULT...OCCASIONAL GUSTS TO
30 MPH WILL BE POSSIBLE...AS WELL AS RELATIVELY MILD OVERNIGHT
LOWS DUE TO CONTINUED DOWNSLOPE WARMING AND MIXING. A TIGHTENING
GRADIENT IS ALSO DEVELOPING OVER LYNN CANAL...WITH NLY WINDS
RANGING FROM 15 TO 25 KT EXPECTED TO PERSIST TODAY AND TONIGHT.
FINALLY...THE DEEPENING LOW OVER THE SRN PANHANDLE WILL RESULT IN
NWLY WINDS TO 25 KT LATE TONIGHT OVER OUTSIDE MARINE ZONES
41...42...AND 43.

HI-RES ARW WAS USED TO REFRESH INHERITED WINDS...AND THEN MANUALY
MODIFIED FOR LOCAL EFFECTS WHERE NECESSARY. POP AND QPF WERE
UPDATED WITH AN INHERITED/GFS/NAM BLEND...AND SKY COVER WAS
AGGRESSIVELY TRIMMED OVER THE NRN PANHANDLE LATE THIS AFTERNOON
INTO TONIGHT.

.LONG TERM...STUBBORN UPPER LOW STILL ANCHORED JUST EAST OF HYDER
WILL KEEP SCATTERED TO ISOLATED SHOWERS OVER THE SOUTHERN THIRD OF
THE PANHANDLE TUESDAY. MEANWHILE A THERMAL TROUGH SETTING UP
TODAY WILL STRENGTHEN INTO TUESDAY MORNING. THUS WITH HIGH
PRESSURE BUILDING OVER THE CANADIAN YUKON...OFFSHORE WINDS MONDAY
NIGHT WILL STRENGTHEN INTO TUESDAY MORNING BEFORE RELENTING INTO
TUESDAY EVENING. ARW SUGGESTING PEAK WINDS WILL OCCUR AROUND 18Z
TUESDAY. AT THIS POINT...MAINLY DUE TO LOWER CONFIDENCE, WE HAVE
LIMITED GUSTS TO 35 MPH FOR DOWNTOWN JUNEAU/DOUGLAS. GENERALLY
THESE WEAKER TAKU- LIKE WINDS OVER JUNEAU ARE MAINLY A COOL SEASON
PHENOMENON. THEREFORE, CONFIDENCE IS LOWER. BUT GIVEN BETTER
MIXING FROM SOME FANTASTIC HEATING...WIND GUSTS ACROSS THE
MOUNTAINS SHOULD HAVE LITTLE TROUBLE DESCENDING TO THE CHANNEL.
LIKEWISE...NORTH- SOUTH PASSAGES OVER THE NORTHERN PANHANDLE WERE
INCREASED SIGNIFICANTLY, BUT NOT TO THE 25 OR 30 KT SUGGESTED BY
THE ARW. ASIDE FROM A CONTINUED NORTHERLY SMALL CRAFT THROUGH LYNN
CANAL TUESDAY AND THE POSSIBILITY OF A RETURN SOUTHERLY LATE
WEDNESDAY AFTERNOON...ASIDE FROM A NORTHWEST SMALL CRAFT OVER THE
SOUTHERN OUTSIDE WATERS...ALL MARINE WINDS SHOULD REMAIN BELOW
THIS CRITERIA.

TEMPERATURES WERE RAISED AROUND 7 DEGREES IN SOME PLACES TO
ACCOUNT FOR HIGH 850 MB TEMPERATURES OF 10 TO 13 C AND ADDED
COMPRESSIONAL HEATING. EIGHTY IS POSSIBLE ALONG THE HAINES HIGHWAY
WITH 70 PLUS TEMPERATURES ATTAINABLE FROM YAKUTAT TO JUNEAU DOWN
TO SITKA. SOUTHERN AREAS WILL REMAIN COOLER BECAUSE OF THEIR
PROXIMITY TO THE COLD UPPER LOW ITSELF AS WELL AS THE HIGHER
PROBABILITY OF SHOWERS.

MOISTURE FROM THE UPPER LOW WILL RE-ESTABLISH ITSELF OVER THE
NORTHERN PANHANDLE LATE TUESDAY NIGHT INTO WEDNESDAY AS OFFSHORE
WINDS ABATE. ISOLATED TO SCATTERED SHOWERS WILL THEN FOLLOW INTO THE
NORTHERN PANHANDLE ARRIVING FROM THE SOUTH. IN RESPONSE TO SOME
RIDGING AHEAD OF THE SECOND BIG UPPER LEVEL SYSTEM, THESE SHOWERS
WILL LIKELY BEGIN DIMINISHING LATE WEDNESDAY...WHERE WE CURRENTLY
CARRY A CHANCE OF RAIN. WITH BROAD AGREEMENT BETWEEN THE GFS AND
THE ECMWF WE RAISED THE LIKELIHOOD OF RAIN ACROSS THE PANHANDLE
FOR THURSDAY AND THURSDAY NIGHT WHILE COOLING TEMPERATURES TO NEAR
60 AS WELL.

LOOKING TOWARD THE WEEKEND...OUR EXPERIENCE WITH THESE SUMMERTIME
CUT-OFF LOWS IS THAT THEY STICK AROUND FOR DAYS. OUR CURRENT BEST
GUESS IS THAT THE LOW WILL DROP SOUTHEAST LATE IN THE WEEKEND
POSSIBLY OFFERING SOUTHEAST ALASKA YET ANOTHER SMALL BREAK FROM
THE PRECIPITATION AS IT FLOATS TO OUR SOUTH. HOWEVER, 00Z MODELS
AS WELL AS THE 06Z GFS INDICATING DEEP SOUTHWEST FLOW MOVING IN
TIME FOR THE NEXT WEEK. THIS COULD MEAN A WETTER PATTERN FOR NEXT
WEEK.

USED ECMWF/NAM FOR MID-RANGE UPDATES AND WPC AFTERWARDS. FORECAST
CONFIDENCE IMPROVING OVER THE MID-RANGE...FALLING TOWARDS THE
WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-041>043.

&&

$$

GARNER/ADKINS

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU


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