Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 281407
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
607 AM AKDT THU JUL 28 2016
.SHORT TERM...A low south of the Kenai Peninsula remains nearly
quasi-stationary but will drift slowly to the east over the next
24 hours. An associated front moved over Southeast Alaska early in
the night and post frontal showers continue to push onshore.
Moderate to heavy rainfall was recorded across all of the
panhandle overnight, but those rates are expected to let up
through the next 24 hours and TPW imagery is indicating the
heaviest rain has already moved inland. Still, some locations
will see heavy shower activity this morning. A flood warning for
the Taiya River remains in effect. See hydrology section below for
details. Shower activity is forecast to diminish later this
afternoon...beginning along the southern outer coast. As the low
itself drifts east, the precip maxima will shift east as well, but
the overall trend will be for categorical precip to taper off
somewhat through the period. Convective parameters evaluated as not
being of sufficient strength to result in thunderstorms, hence
they have not been included with the morning forecast.
Post frontal winds over the gulf have come up to marginal small
craft intensity over the northern and central gulf. A weak barrier
jet is forecast to develop west of icy bay later this morning and
remain into the early portion of the extended range forecast. Sea
states in this area getting up to 8 feet, but remain below small
craft levels elsewhere. A high pressure ridge over the panhandle
and oriented parallel to the outer coast will interact with a
trough of low pressure moving east across southern Yukon later
today. Resulting gradient pinching will increase winds over the
far northern inner channels later today. Have gusty conditions in
the forecast for Skagway and northern Lynn Canal, but no small
craft advisory issued. Elsewhere, no wind concerns.
No changes to pressure grid, but did increase winds over the gulf
a bit. Blended in NAM DNG5 pop and QPF to existing grids. Temps
from both NAM and GFS MOS. Overall forecast confidence is average.
.LONG TERM...Friday through Thursday...Period begins with a pair
of upper troughs over the gulf. One shortwave will drop SE along
the outer coast Fri night into Sat. As this wave moves into
southern British Columbia, the other upper low, currently SW of
Kodiak, will drift into the W gulf. This will induce shortwave
ridging over majority of AOR. Models in fairly good agreement that
the upper low will slide ESE from around 53N/155W Sat morning
into the Pacific NW on Mon. This weak ridging will help diminish
shower activity this weekend, but with onshore flow prevailing,
cannot rule out precip completely and maintained mention of
isolated showers, especially at elevation.
Model solutions in fair agreement with another upper low
developing over E Bering/SW AK early next week and migrating into
the Gulf of Alaska by mid next week. Although solutions diverge
with the strength, timing and location of this feature, leading to
decreased confidence in any one solution. However,the upper level
pattern supports a return of wet and active weather across SE AK
for the latter half of next week.
.AVIATION...Low VMC conditions will give way to IMC at times for
both cigs and vsby. Low level turbulence or chop due to 30-35 kts
at 5000ft early this morning will diminish by late morning. No
wind shear concerns at this time.
.HYDROLOGY...The Taiya River continues to rise and was at a stage
of 16.9 feet as of 5am AKDT this morning. Observed rise matches
the current forecast level closely, but is lagging behind the
prediction by approximately 4 hours. Forecast crest of 17.3 feet
still likely, but will occur later this morning vice late this
past night. Other southeast waterways exhibiting various trends
both up and down in response to rain/showers, but are all well
within their banks and expected to remain so. Possible exceptions
will be Montana and jordan Creek near Juneau, depending on how
heavy the local shower activity is today.
MARINE...Small Craft Advisory for PKZ052.
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