844 
fxus65 kslc 300330 
afdslc 


Area forecast discussion 
National Weather Service Salt Lake City Utah 
929 PM MDT Friday Aug 29 2008 


Synopsis...weather will get increasingly active this weekend as a 
strong storm system dives into the Great Basin Sunday and then slowly 
tracks across Utah on Monday and Tuesday. Southerly winds ahead 
of the system tomorrow will bring hot temperatures to the forecast 
area. 


&& 


Discussion...upper level trough churning over the Gulf of Alaska is 
still on track to bring significant changes to the weather across 
the area for the Holiday weekend. Southwest flow increases tomorrow 
ahead of the trough...drawing moisture into southern Utah. Result 
will be isolated to scattered showers and thunderstorms tomorrow 
over mainly the southern tier. However...a well-mixed airmass will 
also result in a brief return to warmer temperatures...especially 
across the north. 


Moisture continues to surge into northern Utah Saturday night into 
Sunday. With a shortwave disturbance moving across Utah Saturday 
night and large-scale lift ahead of the main trough on 
Sunday...expect precipitation to become more widespread through 
Sunday. Strong and gusty winds will also be common across many areas 
on Sunday. A strong cold front will then enter northwest Utah Sunday 
evening and push southeast across the County Warning Area through Monday. 
Unseasonably cool temperatures will settle into the area behind the 
front with snow levels across northern Utah lowering to near 8000 
feet. Thus...expect rain on Monday with snow over the higher 
elevations of the northern mountains. Exception could be southwest 
Utah which looks to become drier on Monday. 


A cool but drier west to northwest flow will continue through at 
least the middle of next week. Models continue to diverge on the 
system for late week...but current trends are less promising for any 
significant weather. 


No updates this evening. 


&& 


Hydrology...monsoonal moisture will be drawn north into the 
state beginning Saturday...ahead of an approaching strong Pacific 
storm system. Precipitable water values in excess of one inch are 
expected to be common across Utah by Sunday afternoon...with areas 
of heavy rainfall expected. As a result...an elevated risk of flash 
flooding will exist throughout the Holiday weekend. Locations of 
greatest concern are the flood prone areas of southern Utah... 
where precipitation is expected to begin by Saturday afternoon... 
as well as recent burn scars across northern Utah...most notably the 
Corner Canyon area near Draper. 


&& 


Aviation...southerly drainage winds will develop at the slc 
terminal by 04z. South winds will then increase through the weekend 
ahead of an approaching storm system. 


&& 


Fire weather...southerly winds will increase tomorrow ahead of an 
approaching storm system. While humidities will increase across the 
south...northwest Utah will remain on the dry side. A Fire Weather 
Watch remains in effect for zones 420-423 for Saturday afternoon and 
evening for winds/rh. Winds will become stronger on Sunday...but 
deep layer moisture will surge north across the fire 
district...resulting in scattered to numerous showers and 
thunderstorms with wetting rain. Temperatures will then become much 
cooler for Monday and Tuesday...especially over northern 
Utah...behind a strong cold front. 


&& 


Slc watches/warnings/advisories... 
Utah...Fire Weather Watch from 1 PM to 10 PM Saturday for 
Utah fire weather zones 420 and 423. 


Wyoming...none. 


&& 


$$ 


Cheng 


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