332 
fxus65 kslc 190910 
afdslc 


Area forecast discussion 
National Weather Service Salt Lake City Utah 
310 am MDT Friday Mar 19 2010 


Synopsis...cooler air will spread into the region behind the cold 
front today. High pressure with a warming trend will prevail for 
the weekend. 


&& 


Discussion...water vapor loop shows a shortwave moving across 
southern Nevada as another disturbance drops south across eastern 
Idaho. Ridging dominated the West Coast. 400-250mb acars wind 
observations show a 90-125kt northerly jet from British Columbia 
south across eastern Washington and northern Idaho. 00z 700mb 
analysis shows a cold front crossing central Utah...though the 
coldest airmass was nearing southern Idaho. Slight warming is 
currently occurring locally with -6c reported at kslc with -5c 
upstream at kboi. 00z kslc radiosonde observation shows 5c of cooling through the 
column...except 10c of cooling near 700mb during the past 24 hours. 


GOES/RUC precipitable water indicate values range between a quarter 
inch across northern Utah and a half inch near the Arizona border. 


Convectively enhanced precipitation which developed along the cold 
front last evening across southwest Utah is diminishing with the 
loss of instability overnight judging by local radars and infrared 
satellite. By morning expect remnants to be crossing the Lake Powell 
area...where have placed a high chance of accumulating 
precipitation. 


Attention shifts northward during the daytime hours as the cold core 
aloft (-28 to -30c at 500mb) arrives. This is expected to aid in the 
development of numerous to widespread snow showers across the 
northern Wasatch mountains...Uinta Mountains and southwest Wyoming. 
As of this writing...snow has develop across much of Wyoming 
southwest of Riverton and Casper. The amount of cold air arriving 
today should yield snow ratios on the order of 15:1 across southwest 
Wyoming to 20:1 in the adjacent mountains. Both the NAM and local 
WRF-nmm (based on the gfs) suggest a quantitative precipitation forecast bullseye across eastern 
Uinta County as the reinforcing cold air arrives on northeast flow. 
With forecast snow totals in the 3-6" range and potential impact on 
Interstate 80...will be issuing a Snow Advisory...though the western 
portion of the County is expected to see less snow...closer to 2". 
The advisory will also continue for the Uinta Mountains with no 
change in forecast snow totals. 


21z short range ensembles indicate a good chance of negative lifted 
indices and MUCAPE greater than 50 j/kg this afternoon across 
northeast and east central Utah. Continue to account for the 
instability by choosing convective weather wording. Have also 
retained mention of thunder this afternoon. The best chance of 
showers along the urban corridor will be this afternoon with daytime 
heating contributing to destabilization. 


The Great Salt Lake temperature is currently approaching 8c. The NAM 
BUFKIT forecast sounding is more unstable than last night...looking 
like 2 nights ago...with 400-500 j/kg of lake induced cape and 
14-16kft equilibrium levels. This is enough instability to support 
lake effect snow showers...though now with these conditions 
developing during the daytime hours...local wind circulations are 
not as conducive for this. Instead...expect some enhancement to 
shower activity southeast of the lake late this morning and this 
afternoon. 


The other concern today are the gusty winds behind the cold front in 
southwest Utah. The pressure gradient combined with 40kt 700mb flow 
should continue to support gusts greater than 45 miles per hour in the canyon 
of Washington County along I-15...and the southwest downslope 
portion of the Beaver Dam Mountains. Am concerned that the gusts 
will persist through the afternoon with increasing diurnal 
mixing...but will allow the day shift to monitor and extend if need 
be. Also expecting gusty winds to affect the Lake Powell area 
today...though not reaching advisory level. 


Models indicate ridging redevelops late this weekend...before 
flattening out next week as a storm system crosses the Pacific 
northwest and northern rockies early next week. Currently expect 
precipitation with the cold frontal passage Tuesday. Models still 
not sticking to one particular solution during the middle week...now a 
bit more progressive than yesterday. Did start to raise probability of precipitation as 
timing Monday night and Tuesday has been consistent. 


&& 


Aviation...northwest winds will continue at the slc terminal 
through the overnight hours. There is a 40 percent chance winds will 
become light and variable between 10 and 14z. Ceilings are expected 
to fall below 7000 feet above ground level between 14-16z as a disturbance moves 
through the area...and remain below that level through 18-20z. 


&& 


Slc watches/warnings/advisories... 
Utah...Wind Advisory until 10 am MDT this morning for the canyons of 
Washington County in utz019-518. 


Winter Weather Advisory until midnight MDT tonight for utz009. 


Wyoming...Winter Weather Advisory until midnight MDT tonight for wyz021. 


&& 


$$ 


Public...rogowski 
aviation...Kruse 


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