Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 162343
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
443 PM MST Fri Feb 16 2018

.SHORT TERM...(Tonight through Saturday night)
Issued at 342 PM MST Fri Feb 16 2018

The synoptic pattern featured a closed low off the southern
California coast with northwest flow over the Pacific Northwest
this afternoon. Cirrus emanating from the low was sweeping over
areas along and south of the I-70 corridor. Meanwhile, to the
northwest, an area of mid and high clouds generated by a weak
short-wave trough in northwest flow was approaching northeast Utah
and northwest Colorado.

As the short-wave moves across northwest Colorado tonight light
snow showers will develop over the Elkhead and Park Mountains with
isolated activity possible over the Flat Tops and the Gore Range.
This activity will continue into the early morning hours before
tapering off sometime before noon. This weak `clipper` like system
is expected generate 1 to 4 inches of snow, mainly above 9500
feet in the Elkhead and Park Mountains primarily, so impacts will
be minimal. Meanwhile, to the south skies will be clearing as the
cirrus shield shifts to the south. Clouds over the north will
cause lows temperatures to moderate while lows down south will be
similar to those experienced last night.

In the wake of tonight`s disturbance, flow will be shifting to a
more zonal (west to east) flow in response to another low digging
southward along the coast of British Columbia. Models showed a dry
fetch to the west so do not anticipate any precipitation Saturday
afternoon through Saturday night. Modest warm air advection will
allow temperatures to moderate to levels 5 to 10 degrees above
normal for most locations Saturday afternoon. However, snow cover
over the central and upper Yampa River basins will allow
inversions to hold on, limiting warming there.

.LONG TERM...(Sunday through Friday)
Issued at 342 PM MST Fri Feb 16 2018

Dry and mild weather is expected to continue Sunday with scattered
light snow showers becoming possible late in the afternoon over
the eastern Uinta, Elkhead and Park Mountains. Models still
predicting a prolonged period of unsettled conditions beginning
Sunday night and continuing through much of Tuesday. The heaviest
period of snow is expected to occur Monday and Monday night as a
fairly energetic mid-level low pressure trough sweeps from the
Great Basin eastward across the forecast area. Some differences
apparent between the GFS and the ECMWF with the latter digging
deeper and therefore maintaining showers longer into Tuesday than
the GFS. Based on model QPF, snowfall amounts appear to be largely
advisory level, but that could change with ensuing runs. For
Wednesday through Friday, models diverge greatly with a col over
the area transitioning to generalized troughing. Models clearly
continue to struggle with this setup so difficult to put much
detail in these late periods where there will be a chance for
poorly organized showers, mainly over the higher terrain.

Sunday temperatures are still expected to be well above normal
with highs on Sunday reaching levels close to 15 degrees above
normal for some locations. The storm system which moves through
early next week will drive temperatures back to near normal levels
with the coolest temperatures Tuesday. Expect temperatures to
moderate Wednesday and Thursday, rising to between 5 and 10
degrees above normal across eastern Utah and western Colorado.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 442 PM MST Fri Feb 16 2018

VFR conditions are expected to continue at all terminal sites
through Saturday evening. However, a weak weather disturbance will
move across the northern mountains in western Colorado tonight.
This will bring a few snow showers and brief mountain obscuration,
generally north of a line from KCAG to KSBS. KHDN will see mid-
level CIGS tonight, although they are expected to remain above
ILS breakpoints. This system exits after 15Z Saturday with CIGS
lifting and breaking apart.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...NL
LONG TERM...NL
AVIATION...JDC



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