Weather

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fxus65 kgjt 052153 
afdgjt 


Area forecast discussion 
National Weather Service Grand Junction Colorado 
253 PM MST Monday Jan 5 2009 


..persistent snow and blowing snow expected over most mountains 
tonight through Wednesday... 


Short term...tonight through Wednesday... 
moisture continues to stream into the region this afternoon...and 
will continue to deepen as we move through tonight. Current forecast 
remains on track as at least two systems will be passing through over 
the next 48 hours. First system arrives tonight and expected fairly 
widespread snow to break out over the northern and central mountains 
of western Colorado and across parts of northeast Utah. This wave 
brings a quick 2 to 5 inches to the higher mountains overnight... 
before we see a brief break on Tuesday. The next system arrives 
Tuesday night and Wednesday. This wave will be accompanied by a 
fairly strong warm front...which will actually work against heavy 
precipitation. However...cold airmass over the northern zones will 
remain in place as we work into the overnight hours Tuesday night. 
Deep moisture will overrun this cold dome and expect a fairly 
steady...albeit light...snow to fall over the Park Range. BUFKIT 
soundings support this thinking with cold air entrenched through 
Wednesday morning...along with deep moisture. Persistent snowfall and 
decent 700 mb flow running near 40 kts will be enough to generate winter 
storm criteria for several hours...with snowfall amounts in excess of 
a foot by Wednesday evening. As a result...have upgraded the Winter 
Weather Advisory for zone 4 to a warning. Have also included zone 
5...Steamboat Springs...to an advisory with good orographic component 
squeezing out 6 to 12 inches over the same time period. Temperatures 
are expected to slowly moderate through the period...with the lower 
valleys the last to mix out as we continue to wait for a stronger 
surface front to sweep through. So will continue to undercut guidance 
in the lower valleys. 


Long term...Wednesday night through Monday... 
mop-up underway Wednesday evening as the the strong northwest flow 
weakens and becomes more westerly with warm advection spreading 
across the region. The flow continues to back to the southwest as a 
shortwave ridge scoots across the central rockies ahead of the next 
shortwave trough scheduled for Friday. The GFS has taken a different 
approach for the latest couple of runs...the 06z and 12z runs...in 
contrast the more consistent European model (ecmwf)...and the earlier 00z GFS run. 
This later GFS solution splits the flow and cuts off a low over the 
Desert Southwest. This keeps our forecast area on the dry side... 
between the areas of best energy/moisture to our north and southwest. 
The European model (ecmwf) on the other hand...shows good consistency in bringing an 
open wave across the area on Friday. Therefore...have pretty much kept 
the previous forecast with a good chance of mountain snow developing 
over the north Thursday night then spreading on Friday. However with two runs 
of the GFS with the split solution confidence has suffered. 


The other challenge will continue to be temperatures. Have undercut 
guidance since models have been having a hard time resolving the cold 
and inverted valley areas with the widespread snow cover. 


&& 


Aviation... 
ceilings will continue to lower across the region this evening 
as another Pacific storm moves through. Expect widespread MVFR 
and IFR ceilings to return by 06z with snow becoming widespread over 
the northern and central mountains of western Colorado. Snow is 
expected lower visibilities in kase...kege...keeo...kcag and khdn to 
less than 3 miles at times. Conditions will improve briefly on 
Tuesday with local VFR conditions developing between 15z and 22z 
Tuesday...before ceilings lower once again as another surge of 
moisture moves through. 


&& 


Gjt watches/warnings/advisories... 
Colorado...Winter Storm Warning for the northern mountains tonight 
through 6 PM Wednesday...zone 4. 
Winter Weather Advisory tonight through 6 PM 
Wednesday for the upper Yampa River Valley and the 
central mountains...zone 5/10/13. 
Utah...none. 


$$ 




Short term.....Jdc 
long term......eh 
aviation.......jdc