Small Craft Advisory 512, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JUNEAU AK
335 PM AKDT SUN JUL 27 2014

.SHORT TERM...MAJOR UPPER TROF REMAINS ALONG 145W OR SO WHICH IS
SUPPORTING A FEW SURFACE LOW CENTERS IN AND SOUTH OF THE GULF.
THE FLOW ALOFT IS MOIST BUT IR SATELLITE INDICATES A VERY HIGH
PROB OF CONTINUED RAIN...BUT PERIODIC IN THAT PULSES OF RAIN ARE
MOVING IN THE FLOW. WIND IS SOMEWHAT PROBLEMATIC DUE TO THE MODEL
SPREAD ON HOW TO HANDLE SURFACE DEVELOPMENTS ON THE SOUTH END AND
WHERE THESE WILL TRACK. BEST IDEA HERE IS TO USE A BLEND OF
MODELS TO BRING A WEAK BUT TIGHT SURFACE LOW OFF DIXON ENTRANCE
BY 00Z TUE THEN MOVE IT NORTHWARD. USED 27/12Z GEM NAM AND ECMWF.
CONFIDENCE VERY HIGH ON THE OVERALL WET PATTERN BUT ONLY MODERATE
ON SURFACE LOW AND TRACK.

&&

.LONG TERM...MIDLEVEL VORT LOBE ENTERING THE NRN GULF THIS
AFTERNOON IS FORECAST TO ROUND THE BASE OF A LONGER WAVE TROUGH
MON AFTERNOON...AND THEN EJECT NEWD TOWARD THE COAST OF SE AK BY
TUE MORNING. FORCING FOR ASCENT ASSOCIATED WITH THIS SHORTWAVE
COMBINED WITH PW VALUES AOA 1 INCH AND STRENGTHENING SLY LOW-LEVEL
FLOW WILL SUPPORT AREAS OF MODERATE RAIN OVER THE SRN PANHANDLE
MON NIGHT THROUGH TUE NIGHT. IN ADDITION...30+ KT LOW-LEVEL SLY
JET WILL AID IN NEAR SMALL CRAFT WINDS FROM MARINE ZONE 41 INTO
CLARENCE STRAIT MON NIGHT. PREVIOUSLY MENTIONED VORT LOBE IS THEN
FORECAST TO MOVE INTO THE NRN PANHANDLE BY WED AFTERNOON. AIRMASS
WILL BEGIN TO DRY IN ITS WAKE...RESULTING IN DECREASING CHANCES
FOR RAIN AND POSSIBLE CLEARING SKIES /PARTICULARLY OVER THE SRN
PANHANDLE/. TEMPERATURES WILL BEGIN TO MODERATE AS RESULT...WITH
HIGHS POSSIBLY PEAKING IN THE MID TO UPPER 60S OVER THE SRN
PANHANDLE ON THU AND FRI. ECMWF AND GFS ARE IN FAIRLY GOOD
AGREEMENT WITH THE EVOLUTION OF THE LARGE-SCALE PATTERN THROUGH
THE WEEKEND...AND THEY SHOW MOISTURE INCREASING OVER THE REGION
SUN INTO MON...WHICH WILL CORRESPOND TO AN INCREASE IN RAIN
CHANCES ONCE AGAIN.

A BLEND OF THE GEM/ECMWF/NAM WAS USED TO UPDATE PRESSURE AND WINDS
THROUGH 12Z THU...WITH A TRANSITION TO WPC GUIDANCE USED
THEREAFTER. ENSEMBLE BLEND OF DETERMINISTIC GUIDANCE WAS USED FOR
POP/SKY THROUGH THU NIGHT...THEN WPC FOR THE REMAINDER OF THE LONG
TERM. PREVIOUS TEMPERATURE FORECAST APPEARED TO BE ON
TRACK...THOUGH HIGH TEMPERATURES WERE TRENDED UPWARD GOING INTO
THU AND FRI. FORECAST CONFIDENCE IS AVERAGE.

&&

.AVIATION...WIDESPREAD MVFR IN THE RAIN WITH SOME LOW LEVEL
TRAPPED MOISTURE FOR IFR CONDS PAPG AND OCCASIONALLY AT PAKT.
LOTS OF SCUD ALONG THE MOUNTAINS.

&&

.MARINE...ENDED SMALL CRAFT EAST OF CAPE SUCKLING AS THAT LOW
PULLS WEST...BUT ELDRED ROCK HANGING AROUND 20 KT MAYBE UP TO
25 KT. WITH THE NEXT SYSTEM HAD TO ADDRESS TIGHT PRESSURE SYSTEM
MON AFTERNOON WITH SUPPORT FROM LOW LEVEL JET. ISSUED SOUTHERN
AREAS OUTSIDE SUMNER AND CLARENCE FOR AT LEAST 25 KT.

&&

.HYDROLOGY...RIVERS FINALLY STARTING TO RESPOND TO RAINFALL.
AFTERNOON TRENDS ARE UPWARD BUT NO FLOODING EXPECTED ANYWHERE AT
THIS TIME IN THE NEXT DAY OR TWO.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ035-036-041-052.

JC/GARNER