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Area Forecast Discussion (AFD)

Issued by Fairbanks, AK (AFG)

                            
249 
FXAK69 PAFG 192349
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
349 PM AKDT Sun Aug 19 2018

.SYNOPSIS...
Aloft...
The long wave pattern consists of a ridge over Southeast Alaska
and Mainland Alaska with a trough over the Bering Sea. The long 
wave ridge progresses east late this week as the long wave trough
over the Bering ejects a series of short waves east across 
Mainland Alaska through the week. This eventually pulls the long 
wave east over northern AK late in the week. This means that the
current pattern of a warm and dry Eastern Interior will 
transition to a wet and cool pattern by Tue and remain cool and
wet through the weekend, while the West Coast and Western Interior
remains wet through the week, and the North Slope goes from a dry
and warm pattern to a cool and wet pattern by Tue. 

Moderate south flow aloft over the Alaska Range will keep Chinook
conditions over the southeast Interior through early Tue, before
weakening on Tue and allowing rain to spread over the southeast
Interior.

A strong short wave over southwest Alaska will moves east over 
the Alaska Range on Tue causing the chinook flow to end and 
providing instability which could cause isolated embedded 
thunderstorms in the southeast Interior Tue. 


Surface...
A 1002 mb low southwest of Wrangel Island will persist through 
Mon then weaken. A weather front stretching east from this low to
100 NM north of Demarcation Point, will move to Demarcation Point
to Utqiagvik by 4am Mon, and then move south of Kaktovik to Point
Lay by 4pm Tue, then persist into Wed. High pressure over the
Arctic ocean north of this front will build south to just north of
the Arctic Coast of Alaska by Tue. These features will combine to
cause east winds and fog along the Arctic Coast by Mon that will
persist into Wed. Winds will increase to 20-30 kt by Mon night and 
then persist into Wed. 

High pressure stretching from Southeast Alaska to the Copper River
Basin will persist through Mon night. This is causing gap winds of
35g60 mph through Alaska Range passes that will persist into Early
Tue, with a lull in winds Mon as a front moves over the Range. 

An occluded front from Dutch Harbor to the Kuskokwim Delta with a
warm front the Kuskokwim Delta to Eagle and a cold front from the
Kuskokwim Delta to the Kenai Pen. The occluded front will move o
the Yukon Delta to Kotzebue to Ambler by 4am Mon with a warm front
from Ambler to Eagle and a cold front from Ambler to Anchorage. By
4pm Mon occluded front will lie from the Yukon Delta to a triple
point near Anaktuvuk Pass, with a warm front from Anaktuvuk Pass
to Old Crow and cold front from Anaktuvuk Pass to Denali Park. The
front will then weaken in place through Tue am. Expect rain along
and just north of the occluded and warm fronts, and along the cold
front through Tue am, except in Chinook shadow in the southeast 
Interior. Expect between .25-.50 inch of rain in the Western
Interior and West Coast with this system.

The cold front will move east across the Eastern Interior Tue with
a 999 mb low developing by 4pm Tue near Tanana, and then into the
Yukon of Canada on Wed. This will bring rain to all of the Eastern
Interior on Tue with the rain tapering off from the north on Wed. 
Expect 1-2 inches of rain from Tue pm through Wed with the
heaviest rain along the Alaska Range. This will cause rapid rises
on southeast Interior rivers in the second half of this week but
no flooding is expected at this time.

A 988 mb low over Kamchatka will move to the central Bering Sea as
a 995 mb low by 4pm Wed. This will cause winds to increase over
the eastern Bering Sea Tue night and Wed. 

&&

.DISCUSSION...
Models initialize well and show similar solutions aloft and at 
the surface through Wed. Precipitation shows similar areas of 
occurrence on GFS/ECMF through Wed, with NAM slightly different
locations. Prefer the GFS precip field through Wed. 

Models begin to differ on short wave details on Thu, with
significant difference by next weekend. Will follow WPC idea of
going primarily with ensembles from Fri into next weekend. 

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

&&

.FIRE WEATHER...
Strong winds along the Alaska Range through Early Tue, but RH
generally above 40%.

&&

.HYDROLOGY...
Expect between .25-.50 inch of rain in the Western Interior and 
West Coast tonight through Mon. This will cause slight rise on
Western Alaska rivers this week.

Rain will develop over all of the Eastern Interior on Tue with 
the rain tapering off from the north on Wed. Expect 1-2 inches of 
rain from Tue pm through Wed with the heaviest rain along the 
Alaska Range. This will cause rapid rises on southeast Interior 
rivers in the second half of this week but no flooding is expected
at this time.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Advisory for AKZ223-AKZ226.

Small Craft Advisory for PKZ225.
&&

$$

JB AUG 18