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FXAK67 PAJK 191343

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
443 AM AKST Mon Feb 19 2018

.SHORT TERM.../Monday through Tuesday night/...Two fast moving
features are the focus of the short term. Currently, a weak low
pressure system is creating snow showers along the gulf coast.
Shower activity is mainly along Baranof and Chichagof Island
currently; however, as the low tracks southeast some showers will
likely affect Prince of Wales Island as well. Up to 1 inch of snow
is possible associated with the snow showers. The system is fast
moving so shower activity will not be long lived. Skies will clear
behind the low.

Tomorrow will skies will gradually cloud up as a weak short wave
trough aloft descends southward over the Panhandle. At the
surface, most of the energy looks to remain over Canada which
will keep any showers that do happen to form over the Panhandle
relatively isolated.

Temperatures continue to be slightly cooler than average. Daytime
highs will range from the low to high 30s. Overnight lows will
range from the low 20s to the low 30s. This continues the drier
and colder than normal February thus far.

The most significant adjustment made to the short term forecast
was to speed up the low currently over the eastern gulf and
increase shower activity along the outer coast this morning.
Primary guidance was the 00Z GFS with some input from the 06Z
NAMNest for winds. PoP and QPF from the Canadian NH, NAM NMM, and
NAM DNG. Forecast confidence is above average.

.LONG TERM... / Wednesday through Sunday as of 9 PM Sunday/ A
ridge of high pressure continues to remain in place over the Gulf.
A shortwave and its associated surface low will reach the Alaskan
interior by early Thursday, pushing southeast over the panhandle
and dying by late Thursday night. The ridge looks to flatten later
this week and bring in another system Saturday and another
potential shortwave into the day 7/day 8 timeframe.

Changes to pressure were mostly the result of a GFS/ECMWF blend
early on and continuing with some WPC after Friday. The Sunday WPC
discussion mentions not using the GFS in their own blend due to a
much faster track for Thursday`s system than previous model runs.
However, the latest GFS (at the time of this writing) seems to
line up quite nicely with the ECMWF for the mid-week time range.
Despite a tightening pressure gradient over the northern
panhandle, wind speeds were decreased locally based on MOS
Guidance. And as Thursday`s system ramps up, winds over the Gulf
were increased and will easily reach 35 kt.

Temperatures will be on an increasing trend, before dropping
steadily after Friday. To go along with this trend, the NBM was a
nice middle ground and matching well with both WPC and MOS
Guidance. Thus, maximum and minimum temperatures were raised
accordingly through mid-week.

The NAM/SREF was used early on for changes to POP, which
decreased POP`s for Wednesday`s system and confining any
precipitation/ flurries to the early morning hours. POP`s were
increased for Thursday with precip beginning in the late afternoon
and QPF increased slightly using a blend of the GFS/RFC. Snow
levels were once again raised, but with preliminary snow amounts
of up to 2-3" across the panhandle for Thursday.

Although confidence is still not great through the latter portion
of the period, we have seen a slight improvement compared to


.AJK Watches/Warnings/Advisories...




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