High Wind in Alaska, April 4 to 5, 2017

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
927 AM AKDT Tue Apr 4 2017

.UPDATE...The easterly downslope has been drying the northern
panhandle more than previously expected so have trimmed back the
Chances of rain for the northern part of the panhandle. Should see
the rain spread in late this afternoon across the north central
panhandle and then early this evening for this evening. Otherwise
the rest of the forecast seems to be in line with the current
thinking.

&&

.PREV DISCUSSION......ISSUED AT ... 612 AM Tue 4 Apr

SHORT TERM...Tuesday through Wednesday Night...Surface analysis
and satellite imagery depict low pressure spinning over the SW
gulf this morning with a dissipating front bringing precip to most
of the panhandle. Models in good agreement with another minor
shortwave moving N into the far SE gulf this afternoon. As this
wave rides N along the boundary another low will develop and deepen
as it approaches the region. This will result in another band of
storm force winds moving into the SE gulf late this morning. This
band will lift N to the central-E central gulf Tue night then
weaken to high end gales as it reaches the far N gulf Wed morning.
Strongest winds over land will be felt along the outer coast with
peak over W POW, so elected to upgrade to high wind warning this
afternoon and overnight for AKZ027. Strong winds will also impact
AKZ022-023-028 and marginal gusts to 40 mph possible for AKZ026.
Potential still exists for a burst of strong NE wind for downtown
Juneau and Douglas this afternoon/evening as a weak mountain wave
remains possible. Inner channel winds will peak at gales for
Cross Sound, Frederick Sound and Clarence Strait along with near
ocean entrances of S Chatham and Sumner, with other areas
experiencing advisory level winds. Not much precip overnight due
to downsloping E flow. The downslope will continue over the N
inner channels today as the second front approaches, so precip
chances will remain low until the front moves onshore and flow
becomes more SEly. Overall, little change to inherited forecast
focusing mainly on local effects using NAM as guidance for
adjustments to temp/QPF.

LONG TERM...Thursday into Tuesday...Weakening upper trough over
the western gulf with a Pacific storm track directed well south of
the area is the main pattern for the extended forecast. Long
range models in reasonable agreement for Thu into Fri but
consistency is still an issue for the weekend and beyond. The GFS
has abandon the strong ridge that it was building over the western
gulf over the weekend from yesterday's runs in favor of returning
to the weak trough idea that the ECMWF has championed for the
last two days. Meanwhile the Canadian still retains the building
ridge scenario but the ridge is not as strong as what is depicted
in yesterday's runs. Extended forecast favors the weak trough idea
through the weekend riding on the better consistency from the
ECMWF.

At lower levels, Increasing offshore flow Thu into Fri will be
gradually putting an end to the precip that lingers over the
panhandle from the mid week fronts. Panhandle should be mostly dry
by Fri night as an inverted trough starts to develop over the
south and should mostly stay dry (particularly for the north)
into early next week. Extended models are not as strong with this
trough as they have been the last two days so offshore flow is not
quite as strong as previously forecast leading to more clouds
likely around the area and lower winds. Also more extended models
are favoring at least some short wave energy wandering into the
southern panhandle for the late weekend. Retained the chance of
rain for that area as a result with the increasing confidence.

BC/EAL

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Warning from 1 PM this afternoon to 4 AM AKDT
     Wednesday for AKZ027.
     Strong Wind until 1 PM AKDT this afternoon for AKZ027.
     Strong Wind from 7 PM AKDT this evening through late tonight for
     AKZ022-028.
     Strong Wind through late tonight for AKZ023.
MARINE...Storm Warning for PKZ041-042.
     Gale Warning for PKZ022-034-036-043-051-052.
     Small Craft Advisory for PKZ021-031>033-035-053.
&&

Bezenek

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