Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 132155

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

.SHORT TERM...(Tonight through Thursday night)
Issued at 355 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 57th 90-plus
degree day of 2017. That`s just three shy of the current record of
60 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

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 355 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 18Z TAFS through 18Z Thursday afternoon)
Issued at 1109 AM MDT Wed Sep 13 2017

Isolated showers and thunderstorms will develop over the
mountains this afternoon and early evening, but only a small
chance of showers or thunderstorms moving over TAF sites. That
said, outflow winds from storms in the area are likely to impact
some sites during the afternoon and evening. Gusts up to 35 MPH
are possible. Otherwise, expect VFR conditions for all TAF sites
with CIGS above ILS breakpoints through the next 24 hours.




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