Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
000
FXAK67 PAJK 021355
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
555 AM AKDT TUE SEP 2 2014

.SHORT TERM...BRIEF CLEARING BEHIND THE SHOWERS EXITING SOUTHEAST
ALASKA INTO CENTRAL BRITISH COLUMBIA. PRECIPITATION HAS BEEN
FAIRLY LIGHT AND WAS PRIMARILY BEFORE MIDNIGHT. THE CLEARING HAS
RESULTED IN SOME AREAS OF FOG TO FORM ACROSS THE PANHANDLE.
INTENSITIES HAVE VARIED AS IT FORMS MANEUVERS AROUND AND
DISSIPATES. HOONAH AND WESTERN PRINCE OF WALES ISLAND SEEM TO HAVE
HUNG ON TO THE DENSE FOG BETTER SO THAT HAS PROMPTED A DENSE FOG
ADVISORY FOR THIS MORNING.

THERE ARE SOME CLOUDS THIS MORNING SPILLING INTO THE NORTHERN GULF
AND THEN EASTWARD TO THE NORTHEAST GULF COAST AND PANHANDLE. THINK
THE CLOUDS WITH THE WEAK IMPULSE THAT HAS FORMED THEM MAY PRODUCE
SOME LIGHT RAIN LATE THIS AFTERNOON AND OVERNIGHT COMBINED WITH
THE UP SLOPE FLOW OVER THE TERRAIN.

WINDS ARE EXPECTED TO STAY GENERALLY LIGHT THROUGH TUESDAY AND
TUESDAY NIGHT THROUGH THE PANHANDLE REGION.

.LONG TERM...START OF THE LONG TERM WILL FEATURE QUASI-ZONAL FLOW
POSITIONED OVER THE NRN GULF BETWEEN A POLAR VORTEX OVER FAR NRN
INTERIOR AK...AND A RIDGE LOCATED ACROSS THE NERN PAC. WEAK
EMBEDDED DISTURBANCES MOVING FROM W TO E WILL AID IN
ISOLATED/SCATTERED SHOWER DEVELOPMENT SPREADING FROM THE NRN CWA
INTO CNTRL/SRN AREAS DURING WED AFTERNOON. ATTENTION THEN TURNS TO
RICH SUBTROPICAL MOISTURE SPREADING NEWD FROM THE NRN PAC INTO THE
SRN GULF. DUE TO ZONAL FLOW ALOFT OVER THE CNTRL/NRN GULF...THIS
PLUME OF MOISTURE IS FORECAST TO SPREAD EWD INTO THE SRN PANHANDLE
DURING THU...WHICH WILL YIELD LIKELY RAIN CHANCES. MODEL GUIDANCE
IS THEN IN GOOD AGREEMENT SHOWING A WARM FRONT PROGRESSING NWD
ACROSS THE GULF AS WELL AS THE SRN-CNTRL PANHANDLE THU NIGHT INTO
FRI. HIGHEST PROBABILITY FOR RAIN WILL LIFT NWD WITH THE FRONT
INTO THE CNTRL/NRN CWA...WHILE A BRIEF WARM UP OCCURS S OF THE
FRONT DURING FRI AFTERNOON OVER THE SRN CWA.

MEANWHILE...AN UPPER-LEVEL SHORTWAVE TROUGH IS FORECAST TO EJECT
NEWD ACROSS THE GULF FRI NIGHT INTO SAT. INCREASING ASCENT
ASSOCIATED WITH THIS FEATURE COMBINED WITH MODERATE LOW-LEVEL SLYS
AND A MOIST SUBTROPICAL CONNECTION SUGGEST THAT LOCALLY MODERATE
TO HEAVY RAINFALL WILL BE POSSIBLE FRI NIGHT AND SAT. ATTM...THE
NRN HALF OF THE CWA APPEARS TO BE THE MOST PROBABLE LOCATION FOR
HEAVY RAINFALL. AS THE UPPER WAVE CONTINUES MOVING ENE...PARTIALLY
IN RESPONSE TO A NRN STREAM WAVE DIGGING OVER INTERIOR AK...A
SURFACE FRONTAL BOUNDARY IS FORECAST TO PROGRESS ACROSS THE
PANHANDLE SAT AFTERNOON/NIGHT. RAIN THEN DECREASES WITHIN A POST
FRONTAL REGIME ON SUN AND POSSIBLY MON...BUT THE REDEVELOPMENT OF
SWLY FLOW ALOFT SUGGESTS RAIN CHANCES WILL BE ON THE INCREASE SOON
THEREAFTER.

MODELS HAVE COME INTO BETTER AGREEMENT WITH THE SYNOPTIC
DETAILS...INCLUDING THE EVOLUTION OF THE SUBTROPICAL MOISTURE
SPREADING NWD INTO THE REGION. THUS...FORECAST CONFIDENCE IS
HIGHER COMPARED TO PREVIOUS LONG TERM OUTLOOKS. FEW CHANGES WERE
MADE TO PRESSURE/WINDS...EXCEPT FOR THE SUN AND MON TIME
PERIOD...WHERE THE 12Z ECMWF WAS BLENDED IN WITH THE PREVIOUS
PRESSURE GRIDS IN ORDER TO DEAMPLIFY A LOW OVER THE NRN GULF
INTRODUCED IN THE WPC ENSEMBLE. HIGH TEMPERATURES FRI AND SAT WERE
NUDGED UP A DEGREE OR TWO OVER THE SRN PANHANDLE DUE TO ITS
LOCATION IN THE WARM SECTOR. ENSEMBLE BLEND WAS USED FOR
POP/QPF...WITH MANUAL TWEAKS APPLIED IN ORDER TO BRING THESE
FIELDS MORE IN LINE WITH SYNOPTIC FEATURES.

&&

.AVIATION...LOW CLOUDS WITH MOST CEILINGS BELOW 2000 AND A FAIR
PORTION OF THE CENTRAL PANHANDLE UNDER 800 FT. ALONG THE LOW
CLOUDS IS FOG WITH VARYING INTENSITIES FROM 1/4 MILE TO 4 MILES.
EXPECT THAT THESE LOWER CONDITIONS WILL CONTINUE INTO THE EARLY
MORNING AND START IMPROVING BY 9 AM AND THEN TO VFR CONDITIONS BY
AFTERNOON.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...DENSE FOG ADVISORY UNTIL 8 AM AKDT THIS MORNING FOR AKZ021-027.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-043-051-052.

&&

$$

BEZENEK/GARNER

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






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.