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Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
351 PM akdt Wed Sep 18 2019



Synopsis...
a wet and cool weather pattern that is now in place over northern
Alaska will persist into the weekend. A low pressure system in
the southwest interior will move to the central interior tonight
and across the northeast interior on Fri. This will keep rain
occuring tonight across most of southern and eastern interior and
spread rain east to Tok and Northway late tonight. Expect between
0.25 and .50 inch of rain in the southern and eastern interior
with this system through tonight, with the heaviest amounts in
the Alaska Range.

A cold front trailing the above mentioned low will move east
into the eastern interior on Thu, then push back to the west Thu
night and Fri. This will keep periods of rain going over the
interior into Fri.

A strong low moving into the northern Gulf of Alaska on Fri will
continue north over the eastern interior Fri night and Sat. This
will bring more rain significant rain to most of the eastern
interior Fri night and Sat, with snow at high elevations, and with
snow level lowering during the day Sat. This could cause
significant snowfall to the Alaska Range the the interior above
2000 ft from late Sat into sun.

Aloft...
the long wave pattern consists of a trough stretching from the
Bering Sea over Mainland Alaska, with a ridge over western
Canada. This pattern is expected to remain through the middle of
next week. For nrn Alaska this will mean a wet pattern with near
normal temps, snow on the North Slope, and daytime rain, and night
time mix of rain and snow over the interior and West Coast with
high elevation snow through early next week.

A low aloft over the southern Chukchi Sea will persist into Sat.
This has induced a surface low under it that will persist into
Fri and possible Sat. This will also cause isolated to scattered
showers along between the Bering Strait and Point Hope.

A second low aloft 60 nm north of deadhorse will move to 200 nm
north of utqiagvik by 4pm Thu, and to 300 nm west of utqiagvik by
4pm Fri. This feature also has a surface low under it that will
track west under the low aloft into Fri. This will also cause
isolated to scattered rain and snow near the low center.

A short wave trough now in the western Bering Sea will move to the
southeast Bering Sea by 4pm Thu, over SW Alaska Thu night, and over the
central interior Fri then diminishing. This will keep to spin up
a surface low in the SW interior along the Arctic cold front on
Thu night that will move to the central interior Fri. This will
cause an area of enhanced rain along the Arctic front to move
north with that surface low Thu night and Fri.

Surface...
a 998 mb low 80 nm west of Point Hope will remain quasi-stationary
through 4pm Fri, then deepen to 996 mb Over Point hope on Sat.
This will cause northwest winds 15 kt across the southern Chukchi Sea
along with isolated to scattered rain and snow showers through
Fri.



A second 998 mb low 60 nm north of deadhorse will move to 80 nm
north of deadhorse by 4am Thu, to 100 nm north of utqiagvik as a
1002 mb low by 4pm Thu, then to 300 nm west of utqiagvik as a 1002
mb low by 4pm Fri. There will be isolated to scatterer rain and
snow showers around this feature.

A 992 mb low near McGrath will move to Tanana as a 1000 mb low by
4am Thu, to near ft Yukon as a 1003 mb low by 4pm Thu, then move
to near inuvik as a 1004 mb low by 4am Fri. An occluded front that
extends from this low to Fairbanks, with a cold front from
Fairbanks to Cordova and a warm front from Fairbanks to Dawson,
will move to Tanana to Old Crow by 4am Thu then dissipate as it
over rides an Arctic front. Expect .25-.50 inch of rain with this
low and front over much of the southern and eastern interior
tonight, with the rain spreading east to Tok and Northway late
tonight as the downslope flow there weakens. Will see rain mix
with snow over the western and northern interior tonight on the
leading edge of the front, but due to the warm advection with the
front do not expect any snow accumulation except at above 3500 ft.

SW downslope flow is occuring over the eastern Alaska Range ahead
of this low which will diminish late tonight as the flow turn more
westerly and weakens. This is causing gusty winds in Isabell pass
that are now decreasing, but is causing gusty winds between DOT
Lake and Tok that will continue through midnight/

An Arctic front that extends from the low just north of deadhorse
to inuvik to Old Crow to Bethel will move to inuvik to Arctic
Village to Tanana to McGrath by 4am Thu, then to Arctic Village to
ft Yukon to Denali by 4pm Thu. Expect mixed rain and snow north
and west of the front as the previously mentioned occluded front
overrides the Arctic air. Along the front expect rain, with a
chance of precip will be mainly rain southeast of this front
except above 3500 ft.

The Arctic front will move back west to Old Crow to Livengood to
a frontal wave near illiamna by 4am Fri, then to Old Crow to 990
mb front wave near Ruby by 4pm Fri, with the front stalling in
place Fri night, then moving to Arctic Village to Delta Junction
by 4pm Sat. There will be scattered rain showers east of the
front, with widespread rain along the front, especially near the
front wave Thu night and Fri. Again, precip will be mostly rain
southeast of the front, with mixed rain and snow to the northwest
of the front.

A strong low moving into the northern Gulf of Alaska on Fri will
continue north over the eastern interior Fri night and Sat. This
will bring more significant rain to most of the eastern interior
Fri night and Sat, with snow at high elevations, and with snow
level lowering during the day Sat. This could cause significant
snowfall to the Alaska Range the the interior above 2000 ft from
late Sat into sun.

&&

Discussion...
models initialize well aloft and show similar solutions through
4am Fri. After that time the ecmf and Canadian bring a short wave
from the Bering Sea east into the West Coast of Alaska more
quickly than the NAM/GFS. At this time favor the slower GFS and
NAM solutions, as some of the short wave energy should drop south
into the long wave trough and slow the eastward movement of the
short wave, such both the GFS and NAM show.

At the surface at 15z, models verified several mb too weak on the
surface low north of deadhorse and on the surface low near Bethel.
Models show similar solutions through 4am Fri. From Fri into Sat,
the ecmf is faster than the NAM and GFS on bringing a surface low
from the Bering Sea into the West Coast of Alaska. Following the
pattern aloft, we will go with the slower movement shown the by
GFS/NAM. To account for the low centers being deeper than models
indicate, will boost winds a few kts over what models indicate
for zones 202 203 204 and in the Alaska Range today into this
evening.

With precipitation, models have general agreement through Fri,
then after that time the ecmf bringing precip into the West Coast
quicker than the NAM and GFS. Favor using a blend of the GFS and
NAM for areal coverage and amounts.

Bottom line, will go with the GFS/NAM on most features, use a
blend of the GFS and NAM for precip areal coverage and amounts,
and boost model winds a few kt today and tonight zones 201 202 203
and over Alaska Range.

Coastal hazard potential days 3 and 4...none.

Fire weather...wet and cooler pattern for remainder of the week,
with relative humidity above 40% and temperatures remaining below 60.

Hydrology...
rivers generally steady. No areas of concern.

&&

Afg watches/warnings/advisories...
Wind Advisory for akz226.

&&

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