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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 34 °
• Low: 16 °
• Snow

• Tuesday
• 
• High: 31 °
• Low: 22 °
• Snow Showers

• Wednesday
• 
• High: 31 °
• Low: 22 °
• Snow

• Thursday
• 
• High: 31 °
• Low: 18 °
• Chance of Snow

• Friday
• 
• High: 31 °
• Low: 16 °
• Chance of Snow

Southcentral and southwest Alaska forecast discussion...corrected 
National Weather Service Anchorage Alaska 
1215 PM akst sun Feb 12 2012 


Corrected typos 


Analysis and upper levels...high amplitude long-wave trough is 
centered over the Bering Sea and northwest Pacific with an embedded 
closed low just east of the Kamchatka peninsula. A short-wave 
trough extending from the Pribilof Islands to the northern Gulf 
is lifting northward. Strong southeasterly low level winds have 
been producing downslope drying across portions of the southern 
Mainland. However...these winds will drop off significantly as the 
upper trough GOES through giving these areas a quick shot of precipitation. 


Precipitation type is all snow over southwest Alaska...but southcentral 
has some layers of above freezing temperatures (as indicated by 
the 12z Anchorage sounding) and both rain and snow is being observed 
across the region. In any case precipitation will generally be 
light as the upper trough moves through...with little or no snow 
accumulation. 


A 974 mb low just south of the Alaska Peninsula is tracking 
northward along the east side of the upper trough with the 
frontal system headed for the Gulf of Alaska. Other weak lows 
are embedded within the upper trough over the Bering Sea and 
along the Aleutians. 


Model discussion...the NAM initialized too far west with the 
low approaching the Alaska Peninsula...but is in line with 
NAM/ECMWF/gemglb/UKMET as this low moves into Bristol Bay. 
GFS becomes an outlier with a more easterly track of the main 
low...actually tracking it into the northern Gulf. Therefore... 
will lean heavily toward the NAM solution for this system. Models 
continue to show run-to-run inconsistencies with track of a deep 
Pacific low to the Aleutians Tuesday and then into the Bering Sea. 
There is a general trend toward a more easterly track compared to 
the model runs over the last couple days...so will trend in that 
direction. 


Short term forecast... 


Southcentral Alaska...as upper trough moving across the area exits 
to the north this evening frontal system from low along the Alaska 
Peninsula will quickly move in. Strong downslope winds will develop 
once again out ahead of this front initially confining the bulk of 
the precipitation to the Gulf Coast and Prince William Sound. There will 
be very little temperature advection with this system...so the 
rain/snow line will remain right along the coast with some areas 
switching back and forth. As the front reaches the north Gulf Coast 
late tonight a barrier jet will set up...but it should not last very 
long as strong upper flow will help push the front onshore where 
it will fall apart in the mountains. With the front pushing onshore 
expect strong winds to make it to Thompson Pass and produce blizzard 
conditions. Other places in the Prince William Sound will be too 
warm to see much in the way of blowing snow. 


Although the main low will track inland across the Bristol Bay area 
models indicate a much weaker secondary low forming near Augustine 
Island Monday morning. This low may move into the inlet or across 
the northern Gulf. A more typical scenario is to have a weak low 
in both locations. Meanwhile a strong upper level short-wave will 
move across the Kenai Peninsula and Cook Inlet. The combination of 
the surface low development and upper wave will weaken the downslope 
winds and allow precipitation to move into the western Kenai Peninsula. The 
upper trough will then lift northeast across southcentral Monday 
night bringing an end to downslope winds and bringing a quick shot 
of precipitation to most areas. Once again...with the exception of the 
immediate coast precipitation will be light and any snow accumulation will 
be minor. 


There will be another brief break in the weather over southcentral 
on Tuesday before a front associated with a strong Aleutian low 
moves into the region Tuesday night and Wednesday. There is quite a 
bit of uncertainty with the timing and strength of this front...but 
expect impacts will be similar to current systems with the bulk of 
precipitation along the coast and downslope easterly winds inland. 


Southwest Alaska...conditions over southwest Alaska will rapidly 
change as low moves across Bristol Bay zone and inland tonight and 
Monday. Precipitation will be primarily in the form of snow...but 
don't expect it to last very long in any one location. Thus snow 
totals will be light. High pressure will provide a brief break 
before a strong front arrives from southwest on Tuesday. There is 
potential for blowing snow or blizzard issues with this front... 
primarily along the Kuskokwim Delta coast. However...there is still 
quite a bit of uncertainty in the timing and strength of this front 
to have much confidence. 


Bering Sea/Aleutians...a low just beginning to develop down over 
the North Pacific will rapidly deepen into the 950s as it curves 
northward toward the central Aleutians tonight and Monday. At this 
point there is quite a bit of uncertainty in the track of this 
storm. There is always potential for high impact weather with a 
low this strong...but the exact track will determine which areas 
observe the worst conditions. 


Long term forecast...deep upper low/trough will persist over the 
Bering Sea through the day 4 through 7 time period. Therefore... 
expect little change in the type of weather being observed across 
the Alaska region. 


Aer/alu...watch/warning summary 
public...Blizzard Warning 131. 
Marine...Storm Warning 172. 
Gale Warning...120 125 130 132 138 150 155 165 170 171. 
Fire weather...none. 


Seb Feb 12