Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 250522

Area Forecast Discussion
National Weather Service Grand Junction CO
1122 PM MDT Thu May 24 2018

.SHORT TERM...(Tonight through Friday night)
Issued at 255 PM MDT Thu May 24 2018

High Pressure near the Four Corners will be shifting eastward
tonight and Friday as another deep upper level low moves onshore
and approaches the Western Great Basin. This will allow flow aloft
to swing back to the southwest over the next 36 hours with a slow,
but steady, increase in wind speeds expected. A few light showers
are expected this evening across the Eastern Uinta Mountains in
Northeast Utah and near the Divide north of I-70 in Western
Colorado, otherwise this is a dry forecast for through Friday
night. Temperatures will be climbing another 2 to 5 degrees with a
return of the 90 degrees temps for many of the lower valleys.

.LONG TERM...(Saturday through Thursday)
Issued at 255 PM MDT Thu May 24 2018

Winds are expected to peak on Saturday as an upper level jet
slides over Western Colorado with the hottest day of the season so
far possible with added boost from the southwest flow. Very dry
conditions will be in place with afternoon humidity values
generally under 10 percent with some spots dropping below 5
percent. Cannot stress the significant concerns this brings in
regards to the fire weather conditions on Saturday with almost a
perfect storm of conditions aligning for several hours. Vertical
RH profiles suggest little in the way of cloud cover and mixing
to 500 MB or higher should drive winds down to the surface that
exceed 25 mph, especially across eastern Utah and extreme western

Sunday is looking drier and drier with each run as the upper low
will be slower to kick out, keeping the dry southwest flow aloft
in place for just a bit longer. We could be seeing some influence
from the developing tropical system over the Gulf, which looks to
be blocking things a bit. In any case, pressure gradients are
relaxed a bit on Sunday with speeds under fire weather criteria,
but something we will continue to monitor. The upper low should
finally fill and slog eastward by Monday, allowing cooler
conditions and a subtle uptick in convective potential Monday
afternoon through Wednesday. No real favored areas as we are
looking at the typical Pop-and-Drop type activity.

Latest GFS is advertising more of that dry southwest flow moving
back into the region late Wednesday and Thursday. Sure feels like
early June already.

Temperatures are expected to remain anywhere from 5 to 10 degrees
above normal through this period with the hottest days this
weekend and again late next week.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1121 PM MDT Thu May 24 2018

Winds will follow the typical diurnal terrain trends through
Friday morning with some afternoon breezes kicking in with deep
mixing as temperatures peak well above normal for late May.


Issued at 255 PM MDT Thu May 24 2018

A combination of hot, dry and breezy to windy conditions, in
addition to dry fuels, may lead to critical fire weather
conditions from late Saturday morning through Saturday evening.
Humidity values will drop below 15 percent in many valley
locations with a few spots dropping below 5 percent expect with
strong surface heating (could be the warmest day so far this
season). However, there are still some concerns with the gust
potential over our eastern-most fire zones in southwest Colorado,
so will keep the watch going for now as we are still 36+ hours
out before this event is expected to unfold.

Current focus remains on zones where fuels are listed as critical
from our interagency partners, including Colorado Fire Weather
Zones 200, 202, 207, 290 through 295. While weather conditions
will be similar elsewhere, fuels are not listed as critical.


CO...Fire Weather Watch from Saturday morning through Saturday
     evening for COZ200-202-203-205-207-290>295.



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