High Wind in Alaska, April 6, 2022

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
636 AM AKDT Wed Apr 6 2022

.SHORT TERM...What to do with a strong low entering the eastern
Gulf of Alaska and how its gait slows to a wobble gently reminds
the forecaster of a 1970s toy commercial jingle, "Weebles wobble
but they don't fall down." As a supporting, impressively strong
late season jet of 130 kt escorts the low northward, the low is
eventually left on its own as the river of air streams forward
into western Canada. Thus the low is left to wobble to the north.
While not growing, the "weeble" of a storm still packs a punch
and derives at least a modicum of support from the passing jet
streak to the south. The right exit region of the jet does not
even reach the area until arguably late Thursday to finally
facilitate its demise. But what does this all mean for the
central Panhandle high wind threat?

Ensembles, both from the European and American schools, have all
come in to take the approaching strong low on a track slightly
more westerly than previously forecast. While certainty with
individual wobbles will be low, even wobbles can take you
somewhere. In this case the path leads one to a point in the Gulf
of Alaska just southwest of Yakutat. But the weakening will be
slow. Therefore, we cancelled high wind watches for the central
Panhandle, but replaced their 60 mph potential with gusts of 40 to
50 mph, all because of a mean wobble a storm to the west. Given
the ever slowing progress, we extended the 40 to 50 mph winds well
into Thursday for much of the north.

Finally, rain and precipitation will be light with this system,
keeping in line with the wisdom that blowing systems do not wet,
and wetter systems blow a lot less. Light rain develops across the
south today and slowly advances northward, but offshore flow will
limit its spread at first. In Juneau rain does not become likely
until late evening.

To look at this morning, as the powerful late season storm churns
northward well to the south, a relatively cold air mass persists
across the northern Panhandle with showers of rain and snow mixed
still making their way onshore. While most METAR obs have been all
liquid over night, we cannot ignore the PAYA sounding and derived
model temperature fields at 850 mb of -7 to -8 C supporting a mix
of snow this morning. But surface temperatures are all
significantly above freezing so that snowfall accumulations will
only amount to a dusting at most. As the upper level ridge ahead
of the system to the south builds across the Panhandle from
western Canada, offshore flow should aid in cloud suppression
across much of the central/northern Inner Channels and Coast
Mountains today. This should help stabilize the atmosphere ahead
of the system to the south and reveal and beautiful mid-day and
afternoon for much of the north. Given more offshore winds, some
of our high temperatures may undersell the potential. Fifty
degrees in the north may be possible today.

Now for questions that we still have no great answer for. For now,
we still have all rain as precipitation type for Upper Lynn Canal.
But a presumed positive pressure gradient which should support
northerlies tonight could--and we emphasize <<could>> support snow
melt cooling in a weak overrunning event. MOS numbers generally
keep surface temperatures warm, but interestingly dewpoints are
low, which would be in line with offshore flow. But MOS also is
more pessimistic than models in precipitation actually hitting the
ground. As lack of time overnight did not allow us the luxury of
diving into these questions, we wanted to mention reasons for
uncertainty of ptype tonight, and for that matter, its appearance
at all Wednesday night in Upper Lynn Canal. Thus, a changeover to
snow for Haines and Skagway tonight is not out of the question.
But precipitation should be light. And such light precipitation
might use all its energy and moisture to cool the surface such
that it all evaporates before anything deposits.

In keeping with the longer duration of the low's wobbles into the
northeast gulf, we also kept winds going longer into Thursday
through much of the northern Panhandle. And we doubled down on a
southerly acceleration through Lynn Canal Thursday, but due to the
distance of the low well to the west, we were not as comfortable
with stronger winds in Upper Lynn at this time.

Finally, we see no reason to adjust the warned area of the far
southern Panhandle. While high winds may be more of a stretch in
the Ketchikan area with the new track, the low will be far more
robust as it affects the south, therefore, the threat is still
real. High Wind Warnings for most of Prince of Wales Island,
Ketchikan, and Annette Island are posted from 1 PM to 11 PM today.

.LONG TERM...Looking into the rest of the week, a trough over the
gulf of Alaska with its axis over Kodiak Island, will allow for
Southwesterly flow to continue to stream over the panhandle into
Friday bringing chances of showers to the area. As the low exits
the region on Saturday and Sunday a high amplitude ridge sets up
over the area and looks to lead to drying conditions for the bulk
of the weekend and into early next week.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 1 PM AKDT this afternoon through Thursday
     morning for AKZ023-026.
     High Wind Warning from 1 PM this afternoon to 11 PM AKDT this
     evening for AKZ027-028.
     Strong Wind from late tonight through Thursday morning for
     AKZ021-022-024.
     Strong Wind from late tonight through Thursday afternoon for
     AKZ025.
     Strong Wind from late tonight through Thursday afternoon for
     AKZ020.
MARINE...Storm Warning for PKZ041-042.
     Gale Warning for PKZ022-031>033-035-036-043-051.
     Small Craft Advisory for PKZ011-013-021-034-052-053.

&&

Adkins/Suk

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