Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 252005

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
205 PM MDT Sun Jun 25 2017

.SHORT TERM...(Tonight through Monday night)
Issued at 205 PM MDT Sun Jun 25 2017

High pressure still on track to amplify and center itself over the
Four Corners through Monday due to a trough moving onshore the
Pacific Northwest. Forecast models are still indicating some
showers and thunderstorms developing over the San Juan mountains
Monday afternoon, so will keep that in the forecast package. By
Monday night, high pressure begins to break down at lower levels.

.LONG TERM...(Tuesday through Sunday)
Issued at 205 PM MDT Sun Jun 25 2017

High pressure will also flatten at upper levels (500mb and higher) as
energy moves in from the west on Tuesday morning. 500mb vorticity
fields indicating a wave passing west to east through the UT/CO
border Tuesday morning which correlates to the highest winds
aloft. By Tuesday afternoon, winds at 500mb ease some but lower at
700mb are 20 to 25 kts in most of western CO. Eastern Utah winds
ease as Tuesday progresses and forecast models indicate very dry
air (0.15 to 0.30 inch PWAT) moving across southern Utah into
western Colorado Tuesday afternoon. Did issue a Fire Weather Watch
for Northwest Colorado in anticipation of these locations getting
below 15% RH at the same time the trough is passing through
Thursday and elevating winds. This may need to be expanded, but
these are my most confident areas. Otherwise, left eastern Utah
out of any hilights for now due to the timing of the trough. If
the trough slows down, it`s possible we will need to consider Red
Flag products for Tuesday in eastern Utah too. NE Utah and NW
Colorado look to keep PWAT values near 0.50 to 0.60 inch which
will be enough for convective activity over these areas Tuesday

The Four Corners will remain extremely dry through Thursday. NE
Utah and NW Colorado area is progged to have marginal moisture for
some virga or a shower every afternoon through Thursday. Then,
high pressure is expected to strengthen again over the Desert
Southwest through the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 955 AM MDT Sun Jun 25 2017

High pressure will continue to maintain VFR conditions at the
terminals through the next 24 hours. Hazy/smokey conditions will
remain possible as smoke from the Brian Head fire is transported
into eastern Utah and western Colorado. Winds will be typical
diurnal terrain driven winds. A stray shower or thunderstorm will
be possible over the San Juan mountains today.


Issued at 205 PM MDT Sun Jun 25 2017

Critical fire weather conditions are possible on Tuesday as a
trough moves west to east through eastern Utah and western
Colorado. Winds are looking borderline for Red Flag conditions,
but felt confident enough on the timing of the trough passage to
issue Fire Wx Watches for Colorado zones 200 and 202 for late Tues
morning through Tues evening. If the timing of the weather
disturbance moving through slows down, critical fire conditions
could occur in eastern Utah and more widespread in western
Colorado. For now the weather system looks to bring the winds
through eastern Utah early on Monday before relative humidity
decreases below kept them out of any hilights.


CO...Fire Weather Watch from Tuesday morning through Tuesday evening
     for COZ200-202.



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