Weather Service Report


656 
FXAK67 PAJK 302309
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
309 PM AKDT MON MAY 30 2016

.SHORT TERM...No substantial changes were needed to the first
twenty-four hour forecast. What remains of the upper low that has
wrought up scattered showers from Petersburg and Sitka northward
will continue moving north and thereby shrinking shower coverage.
After evening showers, areas from Juneau northwestward will
likely experience some breaks in cloud cover. While some patchy
fog may be possible in this region, night-time cooling periods are
shorter leading up to the summer solstice. Thus any fog that
forms will be brief and unimpactful.

To the south, an initial leading trough will incite some weak
shower activity late this afternoon before warming aloft re-
stabilizes the atmosphere with light rain developing late tonight
into early tuesday. Where modeled QPF showed greater amounts, we
raised POPs to 100 percent. An upper level trough moving in to the
southeastern Gulf by Tuesday will help stall a surface front
draped across the eastern Gulf. This will also induce more
offshore flow across the north, thereby inhibiting the spread of
rain from the south.

Gulf winds were nudged to the GFS, which together with the ECMWF
and Canadian, followed a slower track of the surface front to the
north. The front itself will push the narrow surface ridge deeper
into Southeast Alaska's interior thereby lightening winds for
Tuesday. Frontal influence may increase winds slightly late
tonight and Tuesday over the south and along the the Eastern Gulf
Coast. Highs Tuesday will reach 55 to 65 degrees with the warmest
zones across the drier north and Hyder. Rain soaked areas will
likely be in the 50s. Forecast confidence generally is good.

.LONG TERM...The extended forecast period will be dominated by a
broad upper level trough extending from the Aleutians into the
central Gulf with south to southwesterly flow directed at Southeast
Alaska. This results in onshore flow with high precipitation
chances and cloudy conditions through the week. Multiple different
shortwaves will round the base of the trough and bring periods of
rainfall to the area. The general surface storm track will take
these waves from the north-central Pacific and into the eastern
gulf before weakening and pulling back to the northwest. The NAEFS
standardized anomalies indicate precipitable water values
remaining at 1-2 standard deviations above normal for this time of
year through the extended period. Heaviest rainfall will be over
the southern panhandle with lesser amounts to the north. Currently
forecasted rainfall totals range from 2-3 inches in the south to
1-2 inches across the north through Saturday. There still are some
differences in track of strength of individual waves but expect
periods of gusty winds to accompany the rainfall through the week.
The exact time of these stronger winds will be finetuned as we
head through the week.

Used the 12z NAM/ECMWF for updates to the forecast through day 4
then the last WPC guidance for the remainder of the long term.
Forecaster confidence is above average in slightly below normal
temperatures with wet and cloudy conditions through a majority of
the week. 

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ041>043-051-052. 
&&

$$

JWA/TPS

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