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Area forecast discussion 
southcentral and southwest Alaska 
200 PM akdt Sat Sep 6 2008 


Model discussion...GFS and European model (ecmwf) 12z initializations and forecast 
solutions through Sun night are reasonable. Model solutions diverge 
after this. The GFS pattern has been more consistent in the upper 
levels/surface where as the European model (ecmwf) has shown significant deviations in 
the last couple of runs. That said...the GFS will be used with some 
modification this forecast cycle. 


Upper levels... 
the ridge over the western Bering Sea and the trough near the Alaska 
Peninsula and the eastern Bering Sea/SW Alaska continue through Tuesday. 
Pattern starts to shift as trough moves over the Mainland and Gulf of 
Alaska on Wednesday. At this time the Bering Sea ridge splits north and 
south as a developing center moves across the western Aleutians. 


Short term forecast... 
the main features of interest is the developing low south of the Alaska 
Peninsula and associated frontal trough approaching the Alaska Peninsula and Kodiak 
Island this afternoon. Low center will bottom out in the middle 980s 
this afternoon and should slowly fill through tonight as it heads 
toward Shelikof Strait. Secondary triple point will move to western 
Bristol Bay tonight and will remain nearly stationary through early 
Tuesday. By this evening...front will extend from the western Alaska 
Peninsula...through SW Alaska...Barren Islands...to the central Gulf of Alaska. 
The front continues into the interior and eastern Gulf on Sun 
afternoon. A couple of weaker low center will hold in the eastern 
Bristol Bay/Alaska Peninsula area sun as upper trough broadens. Model timing on 
next organized center moving toward the Alaska Peninsula differs. For now will 
go with next low not as deep as current center. This center moves to 
south of Cold Bay in the upper 990s Sun night then weakens over 
eastern Bristol Bay Monday afternoon. The associated frontal system at 
this extends from the Bristol Bay center to the Barren Islands to 
over the central Gulf of Alaska. High pressure continues over the 
western Bering Sea through Tuesday. 


Pressure gradients are continuing to increase across the Gulf and 
southcentral Alaska ahead of surface low and frontal trough. Strong 
winds will diminish over the Gulf of Alaska sun...however moderate 
pressure gradients across southcentral will continue brisk gap flows 
into sun evening. Another surge of SW winds on the backside of the 
trough occur over the Gulf of Alaska Sun night. Strong southerly 
winds set up over the Gulf Monday afternoon as well as gap flows over 
southcentral with approach of next low. 
Deep moisture with front approaching the eastern Kenai Peninsula likely to 
produce significant rainfall. Rapid rises in rivers and streams in 
this area likely to cause flooding concerns tonight and Monday. For now 
will go with a flood advisory for Rapid River rises. 


Aer/alu...watch/warning summary 
public...Flood Warning zone 125 
marine...gales 120 125 130 132 140 150 155 160 165 
fire weather...none. 


Rmc Sep 08 

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