Area Forecast Discussion
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FXAK67 PAJK 311312
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
510 AM AKDT FRI JUL 31 2015

.SHORT TERM...SATELLITE IMAGERY SHOWS NICE WSWLY JET OVER AND
SOUTH OF THE SOUTHERN PANHANDLE AND COLD TOPS SPREADING OVER THE
NORTHERN PANHANDLE AT THE MOMENT ASSOCIATED WITH THE DEFORMATION
ZONE ON THE NORTH SIDE OF THE WEAKENING SOUTHERN WAVE. 12 HOUR
OBSERVED RAIN AMOUNTS HAVE BEEN LIGHT TO MODERATE WITH VALUES FROM
A QUARTER TO THREE- QUARTERS OF AN INCH OVER THE SOUTHERN
PANHANDLE. RADIATION FOG HAS DEVELOPED IN THE YAKUTAT REGION AND
FOG AND RAIN HAVE HAMPERED VISIBILITY IN THE GUSTAVUS AREA
OVERNIGHT. RAIN PROGGED TO INCREASE TODAY ACROSS THE NORTHERN
AREAS PRIMARILY WITH THE FORCING OF THE DEFORMATION ZONE. PRECIP
SHOULD BE PRIMARILY SHOWERY IN MOST AREAS AS PRECIP PROCESSES ARE
BECOMING SHALLOWER WITH TIME THROUGH THE DAY.

WITH ONSET OF THE NEW AWIPS VERSION...UPDATED MODEL DATA WAS VERY
LIMITED FOR THIS FORECAST PERIOD. USED NAM12 06Z UPDATES FOR
PRESSURE AND WIND TWEAKS THROUGH THE MARINE ZONES. THEN UPDATED
THERMODYNAMIC FIELDS WITH A GFS/NAM BLEND THROUGH THE
PERIOD...RESULTING IN RAIN AMOUNTS OF ABOUT A HALF TO THREE-
QUARTERS OF AN INCH EXPECTED OVER THE NORTHERN PANHANDLE BY SAT
MORNING. DRYING TREND WILL BEGIN LATE TONIGHT OVER THE SOUTH WITH
THE THREAT OF PATCHY FOG WITH ANY CLEARING. PRESSURE GRADIENTS ARE
WEAKENING AS THE SOUTHERN WAVE MOVES ONSHORE AND THERE SHOULD BE
NO MAJOR WIND ISSUES THROUGH THE PERIOD. ONLY 10-20KT MAXIMUM
SPEEDS EXPECTED FOR A FEW AREAS IN BOTH THE INNER CHANNELS AND THE
OFFSHORE ZONES...INCLUDING LYNN CANAL...WITH THE EXCEPTION OF A
FEW AREAS TO 20-25 KT IN CLARENCE STRAIT THIS MORNING.

.LONG TERM...POSITIVELY TILTED UPPER TROUGH IS FORECAST TO EXTEND
SW FROM THE PANHANDLE ACROSS THE SRN GULF AT THE START OF THE LONG
TERM PERIOD /15Z SAT/. LIGHT SHOWER ACTIVITY WILL BE POSSIBLE
BENEATH THIS FEATURE OVER THE SRN TWO THIRDS OF SERN AK AS WEAK
LOBES OF ASCENT SHEAR ACROSS THE REGION. THE UPPER TROUGH IS
FORECAST TO BIFURCATE AND THEN RECONSOLIDATE INTO A CLOSED LOW
00Z SUN-00Z MON AS IT APPROACHES SRN COASTAL PORTIONS OF THE
PANHANDLE. THE UPPER LOW WILL LINGER OVER THE SRN PANHANDLE
THROUGH MON NIGHT AND SERVE AS A FOCUS FOR SLIGHTLY MORE VIGOROUS
SHOWERS. IN ADDITION...THE UPPER LOW WILL BE ACCOMPANIED BY 500 MB
TEMPERATURES AROUND -21C...WHICH WILL AID IN SUFFICIENT
DESTABILIZATION/CAPE DURING AFTERNOON PEAK HEATING FOR A SLIGHT
CHANCE OF THUNDERSTORMS /OVER THE SRN PANHANDLE/.

MEANWHILE AT THE SURFACE...HIGH PRESSURE OVER THE SWRN/SCNTRL GULF
AND LOWER PRESSURE OVER WRN CANADA WILL FAVOR NNWLY WINDS OVER
MUCH OF THE AREA /WITH THE POSSIBLE EXCEPTION OF SLYS OVER NRN
LYNN CANAL SAT AND SUN/. LOW PRESSURE IS THEN FORECAST TO
GRADUALLY DEEPEN IN RESPONSE TO THE UPPER LOW...SHIFTING SWD
FROM THE SRN PANHANDLE TO HAIDA GWAII MON-TUE. A RIDGE OF HIGH
PRESSURE THEN REBUILDS ACROSS THE GULF...ALL OF WHICH WILL
REINFORCE THE NNWLYS.

MODEL GUIDANCE /ALTHOUGH CURRENTLY LIMITED/ WAS IN GOOD AGREEMENT
THROUGHOUT MUCH OF THE LONG TERM PERIOD. ONLY THE NAM AND GFS WERE
AVAILABLE FOR UPDATES TO GRIDS...THOUGH SIGNIFICANT CHANGES TO
INHERITED WERE NOT NOTED.


&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ036.

&&

$$

WESLEY/GARNER

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