Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 181813
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1213 PM MDT Wed Oct 18 2017

.SHORT TERM...(Today through Thursday)
Issued at 248 AM MDT Wed Oct 18 2017

Dry zonal flow will be over the area today with a few ripples in
the flow. These weak upper disturbances have no moisture to work
on so only scattered mid and hi clouds area expected. The first of
these is evident in IR satellite imagery this morning over UT and
will move over the area this morning and early afternoon.

Tonight and Thursday a strong trough will develop over Arizona and
begin drawing moisture north from Mexico. It will lift northeast
late Thursday afternoon and bring showers to the San Juan
mountains before sunset.

.LONG TERM...(Thursday night through Tuesday)
Issued at 248 AM MDT Wed Oct 18 2017

Models suggest some scattered shower activity will linger over the
San Juan Mountains and portions of Colorado`s central mountains
Thursday evening in the wake of the shortwave trough discussed in
the Short Term section.

On Friday, the mean trough over the western U.S. is expected to
move across the Great Basin bringing the next batch of showers to
northeast Utah and northwest Colorado Friday afternoon. This
activity will fall along and just ahead of the cold front
associated with this feature which models indicate will reach
northeast Utah and extreme northwest Colorado late in the day.
Ahead of the front, southwest winds will become breezy, especially
across northwest Colorado. Snow levels will start above 11,000
feet ahead of the front as 7H temperatures are expected to be
around 5 to 6 deg C. However, as the front pushes into southeast
Utah and southwest Colorado late Friday night, temperatures will
plummet. 7H readings are expected fall to near -6 to -7 deg C
across northwest Colorado bringing snow to the lower elevations in
the evening and possibly the I-70 Corridor from Glenwood Springs
east later Friday night. Though snow becomes likely for the
northern and central Colorado mountains Friday night, the duration
of snowfall will be relatively short lived with drying beginning
over the northern mountains by midnight and winding down over the
central and southern mountains by sunrise Saturday.

As the trough axis continues east on Saturday, lingering snow
showers over the mountains will diminish toward midday. Total
accumulations from this storm still look pretty light and, at this
point, appear unlikely to generate advisory level accumulations.
Latest GFS now in line with the ECMWF and both point to dry
weather returning to the area Saturday afternoon and continuing
through Tuesday as a large ridge of high pressure builds to the
west.

Mild temperatures will continue on Friday, though the arrival of
the cold front is likely to cut short warming across the north
during the afternoon. In the wake of the cold front, Saturday will
be much cooler with afternoon highs running 5 to 10 degrees below
normal. Cold overnight lows are expected in the north Saturday
morning, but the coldest temperatures will arrive Sunday morning
when valleys will be in the 20s with teens in the Gunnison Basin.
This won`t last however, as temperatures are expected to moderate
from Sunday through Tuesday with afternoon highs reaching normal
levels for most locations early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1155 AM MDT Wed Oct 18 2017

VFR conditions will prevail over next 24 hours. Light winds are
expected today with occasional breezes at a few sites in the
afternoon. Mid and high level cloud cover will be present
across southwest Colorado today with increasing clouds tonight
into Thursday as a disturbance approaches from the southwest. Some
isolated showers may develop over the southern high terrain late
Thursday morning and afternoon but should not have any impact on
TAF sites.

&&

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

$$

SHORT TERM...CC
LONG TERM...NL
AVIATION...MDA



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