Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 132341
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
541 PM MDT Wed Sep 13 2017

.SHORT TERM...(Tonight through Thursday night)
Issued at 410 PM MDT Wed Sep 13 2017

Another warm, summer-like day across the region today with
temperatures some 5 to 10 degrees above seasonal for this time of
year. The Grand Junction Airport jumped to 91 degrees under
mostly sunny skies this afternoon! This is now the 87th 90-plus
degree day of 2017. That`s just three shy of the current record of
90 days, set in 1977. However, it`s not looking like we`ll match
that anytime soon as we transition to a more typical fall weather
pattern over the coming days with cooler and more unsettled
weather.

A weak ripple in the flow has combined with residual moisture and
daytime heating to spark isolated orographic convection this
afternoon which will continue through the evening hours. The rest
of the area has remained generally dry as weak high pressure
remains overhead. This ridge will begin to flatten this evening as
southwesterly flow increases over the Great Basin as the upper
level low centered off the coast of California moves further
inland. Midlevel moisture will increase overnight leading to
heavier cloud cover and as a result more mild low temperatures.
Nocturnal showers will pick up across the higher terrain early
Thursday as the low approaches.

Thursday will be an active day, especially in the late afternoon
and evening hours, as the low (eventually making the transition to
an open wave) continues to lift northeast across Utah and western
Colorado. Isolated to scattered coverage of showers and
thunderstorms in the late morning will become numerous by mid
afternoon. Mostly cloudy skies and showery conditions will cool
the region off, resulting in highs near normal for the first time
in several weeks. Showers will continue Thursday night as the
trough progresses into Wyoming with coverage decreasing from south
to north.

.LONG TERM...(Friday through Wednesday)
Issued at 410 PM MDT Wed Sep 13 2017

By daybreak Friday areas north of I-70 will have scattered showers
persisting as the cold front associated with a secondary trough
approaches the region. This trend will continue throughout much of
the day Friday while areas further south will be under drier
southwesterly flow. Frontal passage should occur Friday night into
Saturday morning and, as the cooler air infiltrates the region in
its wake, some light snow accumulations will be possible over the
northern mountains, generally above 10kft.

Southwesterly flow will remain aloft behind this trough, keeping
our forecast area dry through early next week. Temperatures will
transition from being comfortably below seasonal norms over the
weekend to gradually climbing back to normal by Monday. A Pacific
low will intensify across the Pacific Northwest Monday and
Tuesday, tightening the southwesterly wind gradient over our
forecast area. Extended models begin to diverge on potential
solutions on Tuesday with the GFS being more progressive with an
elongated closed low while the Euro splits the parent low. At
this time for our local area, we can look forward to dry and
breezy conditions through at least midweek but cooler and wetter
conditions could return for the latter half of the work week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 538 PM MDT Wed Sep 13 2017

Isolated showers and thunderstorms will continue across the
western slope this evening. A few brief lowerings to MVFR can be
expected in any heavier shower, and winds could briefly gust
upwards of 30 to 40 mph. Activity should diminish after sunset
with only a few showers overnight. VFR to start the day on
Thursday but with showers and thunderstorms affecting most
terminals later in the day, a few lowerings to MVFR vis and CIG
heights may occur.

&&

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

$$

SHORT TERM...MMS
LONG TERM...MMS
AVIATION...MAC



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