Area Forecast Discussion
Issued by NWS Fairbanks, AK

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267
FXAK69 PAFG 282142
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
142 PM AKDT Sun May 28 2017

.DISCUSSION...
Main forecast concern will be fire weather and the potential red
flag issues along the north slopes of the Eastern Alaska Range
over the next 48 hours. The 28/12Z deterministic model suite is in
good agreement through 48 hours (Tuesday 12Z) with differences in
model guidance thereafter including differences in H850
temperatures as well as the handing of an upper low and its
surface reflection just offshore of the western Arctic Coast
after 12Z Tuesday. The differences in H850 temperatures for the
28/12Z run is not quite as severe as previous runs, at least over
mainland Alaska. Generally, the differences between the ECMWF and
GFS are H850 temperatures are 4 to 8 degrees celsius over mainland
Alaska as well as placement and areal extent of the warmest H850
temperatures. In regards to the upper low and its surface
reflection, the NAM is a bit more aggressive and stronger with it
compared to the GFS and ECMWF who are a bit weaker and slower
moving it east.

Aloft...A sharp upper level trough with two closed lows remains
stretched over the west coast from the Chukchi Sea south to over
Kodiak Island. The low over the Chukchi Sea will gradually shift
east towards the western Arctic Coast through Tuesday morning.
Meanwhile, the low over Kodiak low will move north over the
southwest Alaska tonight, then north over the western Interior
towards the Arctic Coast Monday into Tuesday morning. Once it
reaches the Arctic Coast, it will merge with the old Chukchi Sea
low Tuesday afternoon. The resulting low will then move north
over the Arctic Ocean and 80N. There are some differences between
models as noted above regarding the position, strength, and
eventual track. The eastern extend of a ridge of high pressure
over the eastern Interior with a ridge axis positioned north to
south over the Pacific NW, British Columbia, and the Yukon
Territory will be pushed east Monday into Tuesday as the
aforementioned low moves north over the Western Interior.
Southerly, chinook flow upstream of the ridge axis is parked over
the Alaska Range and Interior Alaska through Monday morning before
being moved east. Once the low moves north, the ridge will build
back over the Interior extending west over the Alaska West Coast.
Despite disagreement among 28/12Z model guidance, H850
temperatures will warm (+5C to +8C in the warmest spots) and be
warmer than what we have seen over the last week.

Surface...A weak leeside thermal trough has developed north of the
Alaska Range and will persist and strengthen on Monday and then
lift north Tuesday. The 28/12Z NAM is developing a 1005 mb low
over Wainwright Tuesday morning as the upper level low moves
overhead and move offshore as a 1001 mb low Tuesday evening.
However, the GFS and ECWMF paint a weak trough along the North
Slope with the GFS eventually developing a weak 1007 mb low
Tuesday evening north of Barrow. Meanwhile, high pressure will
build over southern mainland Alaska Tuesday and Wednesday.

Arctic Coast and Brooks Range...Expecting a return to low ceilings
and fog later this evening as winds shift from drier, offshore
flow to the easterly flow. Some areas of light freezing drizzle
may accompany the intial surge of low ceilings and fog. Winds
will come a bit along the Beaufort Sea coast tonight into Monday.
As the aforementioned upper low moves north over the Brooks Range,
may see up to 0.50" of rain with some snow mixing in at higher
elevations over the central Brooks Range Tuesday and around 0.10"
of rain north of the Brooks Range late Tuesday afternoon and
evening.

Eastern and Central Interior...Leeside thermal trough north of
the Alaska Range is producing gusty winds along the north slopes
of the Alaska Range, especially near the Alaska Range passes.
Gusty south winds will increase slightly Monday as the thermal
trough strengthens. These gusty south winds will weaken once the
trough lifts weakens and lifts north. As the upper low moves
north over the Western Interior, there will be the potential for
isolated to scattered showers Monday over the Central Interior and
southeastern Brooks Range. There will be a brief 6 hour period
late Monday afternoon and early evening where the Middle Tanana
Valley may see a few showers. There is the potential for isolated
thunderstorms Monday afternoon and evening over the central
Interior and along the southeastern Brooks Range. A warming trend
towards near to slightly above normal temperatures is expected
after Monday once the upper level ridge builds overhead.

Western Interior and West Coast...It looks to be a rainy, wet
Monday and Monday night from McGrath north over the Middle Yukon
Valley and south facing slopes of the Brooks Range, where 24 hour
rainfall accumulations range between 0.25" to 0.75" from 18Z
Monday to 18Z Tuesday. There is the potential for isolated
thunderstorms Monday afternoon and evening from the lower Yukon
northeast over McGrath to Galena and Huslia. Once the ridge of
high pressure builds over the area, thunderstorm potential will be
limited and capped Tuesday through the rest of the week.

&&

.FIRE WEATHER...
Fire weather concerns will increase this week as temperatures
rise, and fuels dry under the influence of wind, warm, and mostly
sunny conditions. The main area of concern will be along the north
slopes of the eastern Alaska Range, particularly along the
Richardson Highway from Isabel Pass north to Delta Junction.
Minimum RH values are expected to drop into the 20s this afternoon
and Monday. Sustained winds are expected to top out around 25 mph
with gusts to around 40 mph through Monday evening, the strongest
winds will be Monday. Will need to monitor, especially on Monday,
as meteorological conditions locally flirt with Red Flag
conditions. Meteorological conditions will be similar along the
Parks Highway north of McKinley Park flirting with meteorological
red flag conditions, but fuels are not dry at this time to for
red flag concerns.

Winds will be lower, but breezy over the rest of the Interior
with minimum RH values in the 20 to 30 percent range. Temperatures
will gradually warm with daytime highs in the lower to mid 70s by
the middle of the week. At this time fuels are not dry at this
time for red flag concerns, however will have to monitor given the
transitions from a cool/wet pattern to warm/dry pattern.

&&

.HYDROLOGY...
Some moderate rainfall from McGrath north over the middle Yukon
Valley and to the south facing slopes of the Brooks Range Monday
and Monday night. 24-hr rainfall accumulations from 18Z Monday to
18Z Tuesday range from around 0.25" to 0.75". Not expecting any
hydro issues relating to this rainfall.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Brisk Wind Advisory for PKZ240-PKZ245.
&&

$$

LTH MAY 17



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