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Northern Alaska forecast discussion 
National Weather Service Fairbanks Alaska 
500 am akdt Friday Jul 4 2008 


Discussion... 
overall the models remain in decent agreement in the short term 
through the weekend...but major differences show up by early next 
week. A closed 500 mb high center about 300 miles west of Banks 
Island will remain in place and extend into northern Alaska through 
the weekend. 500 mb heights will be on the order of 100 dam above 
seasonal averages up along the North Slope. Across much of the 
interior the 500 mb heights will be close to seasonal averages and 
even a bit below by Sunday. The other items of interest include a 
potent low in the central Aleutians that will only very slowly 
push out into the western Gulf of Alaska this weekend. The models 
are reasonably consistent with this feature into the weekend but 
depart significantly by early next week. The last significant 
feature is the "old" low across the MacKenzie River Valley that 
the models whip back to the west and into the interior by Sunday. 


Interior...for most of the interior today will be another dry and 
very warm day. Highs yesterday were in the low-middle 80s in most 
spots...and today will likely be a little warmer still. The low 
at pafa so far this morning has been a balmy 66f...and this is 
15 degrees warmer than at time yesterday! The 00z sounding had an 
850 mb temperature of +14c which was right on the mark for what all of 
the models were advertising yesterday. The sounding was also very 
dry and stable as expected. The 12z sounding has moistened up a 
bit but little/no additional warning noted between 850-500 mb. 


The thermal trough today looks to set up along the crest of the 
Alaska Range. This will keep the most unstable air across the 
Alaska Range and the upper Tanana Valley. It looks to dry and 
stable further north for any convection. In fact the cumulus rule 
indicates little in the way of cumulus formation in the middle Tanana 
Valley...and if there is any cumulus the bases will be up around 10k feet 
above ground level. By the time Saturday rolls around heights begin to fall a 
bit across the central and eastern interior and the atmosphere 
gradually becomes a bit more moist and unstable by the afternoon 
as some higher Theta-E air gets advected in from the Yukon. This 
will lead to isolated showers and thunderstorms in the 
afternoon...mainly across the southeast interior. By Sunday a few 
showers and thunderstorms will be possible across much of the 
central and eastern interior. 


North Slope...aside from times of fog and a moderate east/northeast 
wind...especially along the Beaufort Sea coast...the weather will be 
relatively benign. Inland temperatures will be above average. 
Overnight the only observation site to be in the soup was Nuiqsut 
with visibilities down to a quarter mile at times. A few patches 
of stratus elsewhere...but unlike yesterday morning the fog has 
not been widespread...at least not yet. 


West Coast...the best chance of showers will be today and tonight 
across the southwest zones which will be closest to the storm system 
in the Aleutians. As this low drops southeast over the weekend the 
West Coast will be dry with above average temperatures. 


Midrange...long range difficulties continue as models still having 
difficulty handling cold closed low north of Siberia and the 
evolution of upper low presently moving into the Gulf of Alaska. 
Decent agreement though on substantial ridging over the western 
Bering Sea early next week and default ridge over the interior...though 
heights not especially high. 12z European model (ecmwf) aggressively moving deep 
polar vortex toward wrangel island by mid-week..but given history 
the past six weeks or so this is not a good bet...with operational 
18z GFS and 12z GFS ensemble mean solution of keeping the low much 
farther northwest looking better. From what we can tell from the 12z 
naefs..the mean is also trying to move the low southeast...but with big 
spread in the solutions. No doubt related to the higher latitude 
feature...the European model (ecmwf) is keeping much lower heights vicinity Kodiak 
Island through middle- week. This has little or no support from the 18z 
GFS or 12z GFS ensemble mean or the naefs. Overall...continued warm 
middle-Summer weather with the chance of convection in the interior 
seems the best bet...but with at least the chance of larger scale 
west-SW flow into northwest Alaska by mid-week. 




Coastal hazard potential days 3 and 4...none 


&& 


Fire weather...another toasty and mainly dry day across the 
interior with widespread highs in the 80s...and like yesterday 
the min rh's will tumble into the teens at many spots this 
afternoon. An east to northeast wind of 10 to 20 miles per hour with local 
gusts to 30 miles per hour will combine to produce critical fire weather 
conditions this afternoon and evening. Saturday will likely also 
be a critical fire weather day across parts of the interior with 
low rh's and wind. By Sunday the wind should die off and the rh's 
will not be as low as the previous few days...but there will be an 
increased chance of convection on fuels that have had a good 
opportunity to dry out. 


&& 


Hydrology...none. 


&& 


Afg watches/warnings/advisories... 
red flag warning for akz219-akz220-akz221-akz222. 


Small Craft Advisory for pkz210-pkz220-pkz225-pkz230. 


Brisk Wind Advisory for pkz240-pkz245. 


&& 


$$ 


Cumulonimbus/rt Jul 08 

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