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 31 32
000
FXAK67 PAJK 221356
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
556 AM AKDT Mon May 22 2017

.SHORT TERM...Yesterday`s front has split into two factions. The
northern half of the region is seeing numerous showers associated
with the remnant low center that moved inland near PWS last night.
Majority of these showers are occurring along the outer coast
near Pelican and northward to Yakutat. The southern half of the
region is seeing widespread rain with rates of moderate to heavy
at times. Both areas with precip falling has low clouds or fog
with visibility around 3 miles. The interesting part of the
panhandle is a small portion of the central panhandle encompassing
Juneau/Gustavus/Hoonah/Angoon/Sitka. These towns have had little
shower activity overnight and have more of a mid-level cloud deck.
The overall thinking is that some of the showers to the north
will shift south through the day or more will fill in from the
gulf, but at this point the POP is looking on the high end for
this gap.

Winds remain strong out of the south through Lynn Canal this
morning. These came up yesterday afternoon post front with Eldred
Rock at gale force and Skagway getting persistent gusts of
40-50mph. Downtown Haines and the Juneau airport are also seeing
gusty winds. Expect winds to gradually ease through the afternoon
as the pressure gradient slackens.

Tonight a new weak low center looks to track E-NE across the
southern gulf. Latest models have shifted the low a bit north as
it moves into the SE gulf. Have adjusted the pressure/wind forecast
accordingly using the ECMWF and GFS for their good agreement on
placement. Expect winds to become light most places overnight,
then turn out of the north on the north side of the low by Tuesday
morning. The low will help to keep showers going over the central
and southern panhandle through tonight, then take the showers
with it as it shifts E-SE through Tuesday afternoon. High pressure
will build over the gulf behind the low and increase the NWLY
flow, which tends to be a drying pattern for us.

.LONG TERM.../Wednesday through Sunday/ As of 10 pm Sunday. For
the start of the long range, at upper levels main features will
be high pressure ridge over the eastern gulf with a low north of
the Bering sea with associated trough extending over the
Aleutians. As the upper low begins to shift to the east the gulf
ridge will narrow and sharpen. By Friday the upper level trough
will have moved over the central gulf with the ridge axis now
moved over British Columbia. For the rest of the weekend uncertain
if a wave will form over the northeast gulf.

At the surface the high pressure ridge will remain over the gulf
through the week. Main difference between previous forecasts is
indications that the trough from the Bering sea low will move a
short wave into the north central gulf and this wave may ride
over the surface ridge and impact at least the northeast gulf, if
not the north central panhandle. At most thinking this would be
scattered to isolated showers mid week but may just move in mid
level cloud cover. As this wave dissipates, a return to high
pressure being the dominant feature. Will be watching for marine
layer formation under this gulf high.

The other trend for the long range is warming temperatures aloft,
with 850 mb temps reaching 8 to 10 C by the weekend. Have
continued to keep warm surface temps in the forecast, but with
uncertainty of marine layer formation have held off on getting
above the upper 60`s, however 70 and higher is not out of the
question. Did drop Yakutat temps a bit due to the incoming short
waves and onshore flow from ridge axis position.

Small craft winds on lee side of the ridge will diminish as the
axis moves east. Indication of tip jet formation near Cross Sound
and Cape Decision so keeping winds at least in the 15 to 20 kt
range for these locations. For rest of the inner channels not
expecting winds to be much more than 15 kt.

Used a blend of GFS/NAM, which were in good agreement for the mid
week wave in the northeast gulf. Tempered down any pops from these
models due to initial uncertainty. Otherwise forecast confidence
is average.

&&

.AVIATION...Precip continues across the panhandle and will
diminish slowly from N to S today. Some breaks in the clouds has
resulted in some patchy fog/low stratus this morning. Meanwhile,
across the N, strong winds will slowly diminish through the
morning. Precip will maintain MVMC/tempo IMC conditions across
the S through the day. Overall, a gradually improving trend across
the region today. Held off on including FG in TAFs attm, but will
need to consider the potential as skies break overnight into Tue.

&&


.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until 1 PM AKDT this afternoon for AKZ018.
MARINE...Gale Warning for PKZ012.
     Small Craft Advisory for PKZ013-022.
     Small Craft Advisory due to Seas for PKZ041>043-051>053.

&&

$$

BC/Ferrin/PRB

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.