Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 271326
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
526 AM AKDT Tue Jun 27 2017

.DISCUSSION...
The 26/00Z 500 mb analysis shows large 505 dm low located in the
High Arctic centered near the Pole at 86.5N 110.5W. An associated
short wave was located southwest of the low in the northwest
Beaufort Sea. Troughing extended further of this low through the
Chukchi Sea into east Siberia, to another area of broad low
pressure over the Bering Sea, with a 533 dm low centered 160 miles
northeast of Atka. Ridging was seen downstream of this long wave
trough through mainland Alaska, with the ridge axis residing
through the central Gulf to Cantwell to Tanana to Point Hope. A
short wave cutoff from the main flow is centered between Central
and Beaver.

At the surface, weak ridge of high pressure was observed over the
Beaufort Sea, with a 1014 mb center located 290 miles north of
Demarcation Point. An expansive area of high pressure was over the
North Pacific around 43.4N 142W, with surface ridging extending to
the northwest with the axis running from Anchorage to Wales. Large
990 mb surface low was located in the southern Bering just west
of the upper low, near 57N 179E. Weak trough of low pressure
extended to the northeast of this low running from Point Hope to
Tanana.

Models for the 27/00Z run of the deterministic guidance remain in
fair to good agreement through the upcoming week into this weekend.
The long wave pattern is expected to remain relatively static
with elongated troughing running from the Bering Sea to the High
Arctic, with some form of downstream ridging influencing the
eastern half of the state. A series of short waves will round the
main upper level circulation in the Bering Sea through the week,
bringing showery weather to the western half. Short wave energy
currently south of the Kamchatka Peninsula will rotate around the
Bering trough reaching the Gulf by Friday morning, to become
cutoff into a new upper low by Saturday morning. This Gulf low
will shove the ridge axis north and east into the Yukon and
northeast AK by Saturday.

At the surface, high pressure over the central and eastern
Beaufort Sea will linger for the remainder of the week, gradually
strengthening to around 1026 mb by Thursday as the high center
drifts over the Canadian Archipelago. Surface low pressure over
the southern Bering will linger in the region as well until the
weekend, but the center is expected to wobble northwestward toward
eastern Siberia coast to merge with lower pressure there by
Thursday, gradually dissipating this weekend. Surface trough over
the central interior will become thermally enhanced today, and
will shift over the Brooks Range and North Slope for Wednesday.
Thermal trough will redevelop over the central and northern
Interior once again for Friday into Saturday.

North Slope: Easterly surface flow will continue today and
persist for the remainder of the week as high pressure builds to
the north of the Arctic Coast. Low level trajectories off the
eastern Beaufort will be favorable for periods of low stratus and
fog for the eastern Arctic coast, as has already been the case
early this morning from Deadhorse east. A break in the fog/stratus
may come late tomorrow as winds just above the surface turn more
offshore, which may continue into Thursday. Strengthening pressure
gradient as high to the north intensifies may prompt brisk
winds/small craft advisories for the Arctic Coast Wednesday into
Thursday morning. A return to a showery regime is expected by
Wednesday/Thursday for mainly northwest Alaska and the western
Brooks Range as pieces of short wave energy eject northward from
cyclonic flow over the Bering Sea.

West Coast: Large upper trough over the Bering will keep showery
weather for the west coast through at least Friday. There will be
some focused chances of rain for the west coast as short waves
rotate north around the parent circulation; the first of which is
bringing light rain to portions of Norton Sound early this
morning, with additional organized shots of rain expected for the
west coast from late this afternoon through Wednesday, and
perhaps a third Friday. Temperatures will range from the the 50s
and lower 60s over the next several days for most coastal
locations.

Interior: Thermal troughing looks to redevelop for the Interior
today with isolated afternoon and evening thunderstorms generally
north of the Yukon River. The focus for convection will shift
further north into the Brooks Range for Wednesday afternoon and
evening. Chances of rain will persist through the week for the
west Interior as weak disturbances rotate northward from the
broad upper low in the Bering Sea, with the best chances from
late this afternoon through Wednesday, and perhaps a once again
Friday. As the last of the waves move north, upper level ridging
to the east will no longer be flattened and will strengthen in
Interior Alaska. The building heights will bring a return to
thermally enhanced troughing back to the Interior and renewed
chances of thunderstorms late this week into this weekend,
especially with increased moisture transport from the
east/southeast as upper low develops in the Gulf. The deep
southerly flow regime developing will promote periods of gap winds
through Alaska Range Passes through this week.


Coastal Hazard Potential Days 3 and 4...None.

&&

.FIRE WEATHER...Gap winds through Alaska Range passes will
persist through the rest of the week with marginal red flag
conditions expected with min RH values falling into the upper 20s
to lower 30s in these areas.

Thermal troughing looks to redevelop for the Interior tomorrow
with isolated afternoon/evening thunderstorms for the central and
northern Interior, generally north of the Yukon River, with the
threat of convection shifting north into the Brooks Range for
Wednesday.

Chances of rain and higher humidity is expected from tomorrow
through the rest of this week for the west Interior as weak
disturbances rotate northward from the broad upper low in the
Bering Sea. Dry weather will persist for the Yukon Flats and
southeastern Brooks Range with min RH values between 25 to 35
percent through this week.

&&

.HYDROLOGY...The Fortymile and Tanana Rivers will continue to run
high for the next day or two due to recent heavy rains last
weekend. River crests are expected to remain at or below bankfull
stage.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory for PKZ230.

&&

$$

NTS JUN 17


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