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Northern Alaska forecast discussion 
National Weather Service Fairbanks Alaska 
347 am akdt Sat Jul 5 2008 


Discussion... 


Weak upper low over the north central Yukon territory 
is expected to drift slowly westward through sun...prefer 
slower speed of movement indicated by GFS/European model (ecmwf) compared to 
the NAM. A second and even weaker upper low is expected 
to develop over eastern zone 223 or northwestern zone 224 
Sat afternoon or evening. These weak upper systems should 
help spark some isolated afternoon and evening thunderstorms 
southeast of Fort Yukon in zone 220 and south and east of 
eielson in zone 222. GFS 700 relative humidity forecast shows increasing relative humidity over zone 
224 and the southeastern portions of zone 222. While model 
soundings for Fairbanks are not bullish on convective potential 
today...we will introduce some isolated thunderstorms in these 
areas based on an expected increase in moisture and some dynamic 
assist from the weak upper lows. Isolated thunderstorms are 
expected in zones 223-224-225-226 with moisture already in place. 
Today...the surface thermal trough will extend from the Northway 
area westward along the southern edge of the Alaska Range. 


For Sunday...an increase in moisture is expected in zones 221 
and 222...and GFS is showing a substantial increase in instability 
with increasing convective available potential energy and lifted indexes as low as -1.5. 
Additionally...the surface thermal trough is expected to migrate 
a bit northward...allowing for an increase in low level moisture 
convergence. 


Over zones 223-224-225-226...convection is likely to be active 
today with the presence of the thermal trough and unstable air...GFS 
showing widespread lifted indexes of 0 to -2 and areas of -2 to -4. 
The unstable airmass is expected to persist over these areas 
Sunday. 


Over the Arctic...GOES visible loop showing an extensive area of stratus 
over areas from Barrow north through southwest...including most 
of zone 201. This stratus is missed by the low level relative humidity forecasts 
on both the GFS and NAM models. This area is likely to remain 
foggy through tonight with onshore flow continuing...although 
visibility may come up some during the afternoon and early 
evening. Dense fog headlines will be posted for zones 201 and 202. 
The eastern Arctic coast is likely to remain fog-free. 


The West Coast areas will remain under dry north to northeast 
flow today and Sunday...except for isolated thunderstorms 
in the extreme south parts of zones 214 and 215 this afternoon and 
evening. Lds picked up an overnight strike in zone 210 northeast 
of Nome...but drying is expected by this afternoon. This indicated 
by GFS moisture forecasts and GOES infrared/vis/water vapor. 




Coastal hazard potential days 3 and 4...none 


&& 


Fire weather... 
northeast winds gusting to 25 miles per hour or more with min relative humidity 
below 30% expected again this afternoon and evening in 
zones 216-219-220-221-222...with a moderate pressure 
gradient between high pressure over the Arctic Ocean 
and the thermal trough extending from the Northway 
area westward. Local gusts to 25 miles per hour possible in zone 
220 Sunday. 




&& 


Hydrology...none. 




&& 


Afg watches/warnings/advisories... 
red flag warning for akz216-akz219-akz220-akz221-akz222. 


Small Craft Advisory for pkz210-pkz220-pkz225-pkz245. 


Brisk Wind Advisory for pkz240. 
&& 


$$ 


Rf Jul 08 

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