Uitleg wetenschappelijke weersvoorspelling
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
255 am akdt Tuesday Jul 7 2015
Models...initialization well vs 06z surface analysis. Run to run
consistency has been good through the weekend. Models have
changed a bit on the handling of the system moving over the
southwest this morning and north over the area today. Heaviest
precipitation in all the models is now over the western Brooks
range with more of a showery regime over the central and eastern
interior. Will use the NAM as the base for precipitation forecast
with a nudge to the sref to get probabilities up a bit.
Aloft...at 500 hpa...ridge lies from high in the North Pacific
over Sitka to burwash Landing Yukon to Fort Yukon to Barrow and
north this morning. The ridge will remain stationary this
afternoon then build a little back to the west and lie from
Yakutat to Wainwright by late evening...then from Cordova to
Wainwright by Wednesday morning and becomes quasi stationary
through Thursday. A large col will cover most of the interior
through Thursday. A 530 dam low over the central Bering Sea will
remain quasi stationary through Thursday. An associated shortwave
has moved over southwest Alaska and will continue to move north
across the state today becoming stationary over the Brooks range
tonight as a trough associated with a 532 dam low just south of
Banks Island Canada swings a shortwave south to the Brooks range.
At 850 hpa...cooling has begun across the state and temperatures
over the interior and wet coast will fall around 5 celsius by
Wednesday morning...while on the North Slope temperatures will
fall up to 10 celsius.
Surface...thermal trough lies Northway to Fairbanks to Huslia to
Teller this morning and will be shoved north today by the weather
front moving across the state from the southwest. The front lies
from St Lawrence Island to Unalakleet to McGrath to Anchorage this
morning and will lie from Kotzebue Sound to Allakaket to Eagle by
late this afternoon...then becomes stationary over the south
slopes of the Brooks range Wednesday morning. From Manley Hot
Springs west stratiform precipitation with areas along the Brooks
range seeing the highest amounts with near an inch by Wednesday
afternoon. From Manley west precipitation will be mainly showery
with some isolated thunderstorms as the front moves through. Areas
along the Alaska Range east of the park and south of a line from
Delta Junction to Chicken will be mostly shadowed out. Some gap
flow winds this morning will persist into the afternoon before
Satellite...sport microphysics modis at 06/821z has some stratus
over the western Brooks range...which may be smoke...and the lower
Yukon Delta. The GOES MVFR/IFR products confirm the stratus over
the lower Yukon Delta...but not indicating the stratus over the
western Brooks range. Modis true color from Monday shows a large
area of smoke covering most of northwest Alaska...the western half
of the Arctic...most areas north of the lower Yukon Delta...and
areas northeast of Delta Junction in the interior.
Arctic coast and Brooks range...cooling across the area with
onshore flow that will bring a return to the stratus and fog to
most coastal areas. Winds east of Wainwright on the coast
increasing to 25 to 35 miles per hour this afternoon and evening from the
east. Winds from Point Lay south east this morning...then
southwest this afternoon as front moves north of them.
West Coast and western interior...along the coast a recurring
theme setting up as low over the Bering Sea remains quasi
stationary and wave spin around the low and over the coast. Bands
of rain will provide some wetting rains over most of the coast and
western interior today. Heaviest rains in zones 208 and 217 but
not enough for any flooding issues. Isolated embedded
thunderstorms today as the front moves through.
Central and eastern interior...mainly scattered showers east of
Tanana...rain from Tanana west...with some shadowing near the
Alaska Range south of Delta Junction. Some gap winds this morning
will taper down in the afternoon. Relative humidity values
remaining above 30 percent. Temperatures down a bit today with
most areas seeing highs only in the 70s. Smoke moving around will
reduce visibility across the area at times to less than one mile.
Extended forecast days 5 to 8...no change from what it was looking
like yesterday...a ridge aloft strengthens over the eastern
interior with thermal trough at the surface. Weak influx of
moisture at the surface with some weak cooling aloft...the
combination will lead to a more convective pattern over the
Coastal hazard potential days 3 and 4...none.
Fire weather...dewpoints on the rise today in the interior and
with more cloud cover and cooler temperatures the relative
humidity values will be up above 30 percent. Winds near Alaska
Range passes will taper down to less than 25 miles per hour this afternoon.
There is potential for red flag conditions on the Arctic slope
this afternoon...so will let fire folks know about that this
morning. Dewpoints start falling tonight but high temperatures
will be in the 60s to around 70 so not much potential for red flag
conditions through Friday.
Hydrology...big change in models since yesterday is now placing
the heaviest rainfall over the south slopes of the western Brooks
range today and tonight. Rainfall amounts of almost an inch are
expected. Do not expect a response in most river and
streams...but some of the smaller streams could become bankfull
for a short time.
Dense smoke advisory for akz207-akz208-akz217-akz219-akz221-
Small Craft Advisory for pkz210-pkz220-pkz225-pkz230.
Gale Warning for pkz230-pkz235.
Brisk Wind Advisory for pkz235-pkz240-pkz245.
Sdb Jul 15