Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 190901

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
301 AM MDT Tue Sep 19 2017

.SHORT TERM...(Today through Wednesday)
Issued at 301 AM MDT Tue Sep 19 2017

Winds will substantially increase today across the region as a
100+ kt jet arrives from the west. Wind advisories are in effect
for parts of NW Colorado from 11am to 7pm today in anticipation
of wind gusts 40 to 50 mph across parts of Moffat, Rio Blanco,
Garfield and Eagle counties. The polar upper level jet is driven
by a sub-Arctic airmass with a seasonably frigid -25C core at
500mb lingering over the US/Canadian western border for a few
days. Forecast models are bringing a few showers into NE UT and NW
CO this afternoon but accumulations should be light and should
stay north of I-70.

The strongest part of the polar jet retreats northward out of
Utah and Colorado on Wednesday, but winds will still remain
breezy across eastern UT and western CO with 60+ kts of upper
level support. No precipitation is expected Wednesday.

.LONG TERM...(Wednesday night through Monday)
Issued at 301 AM MDT Tue Sep 19 2017

A longwave trough splitting off of the parent closed low over the
US/Canada border will swing into the Pacific NW states on Thursday
with the jet axis changing to a more southwesterly orientation on
Thursday. This trough tracks slowly southeastward toward the
Central Rockies late this week. The front along the incoming
closed low is expected to produce showers Friday and Saturday.
This cold front will move very slowly across eastern UT and
western CO as it stalls and weakens this weekend, and forecast
models are keeping temperatures warm enough for snow only in the
highest mountains of northwestern CO.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1100 PM MDT Mon Sep 18 2017

VFR conditions are expected to prevail over the next 24 hours. Mid
and high level cloud cover will increase overnight and be more
prevalent across northeast Utah and northwest Colorado as an upper
level trough approaches. As winds increase aloft, LLWS will occur
overnight until the stronger winds mix down to the surface after
12Z or so, becoming breezy by morning with gusts in the 20s. Winds
will increase late morning into the afternoon as the associated
cold front approaches and moves through the region with valleys of
northwest Colorado and the I-70 corridor including KRIL and KEGE
seeing gusts up to 50 mph. Otherwise, winds will gust into the
30s and up to 40 mph outside of the areas included in the wind
advisory. Some light showers are possible over the northern
mountains but are not expected to pose much impact to TAF sites.
Stronger winds aloft will generate mechanical turbulence over the
ridges and along the lee side of the mountains.


Issued at 301 AM MDT Tue Sep 19 2017

Surface winds will increase across the area today, with the
strongest winds across the northern two thirds of the area. A
broad and strong trough with a series of embedded shortwave
troughs will approach Tuesday and move over the area through the
week. All but the most southern zones should remain too moist with
RH not reaching criteria. Utah zone 491 south of Blanding will
have critical weather conditions but the fuels are not critically
dry. CO zones 207 and 290 have critical fuels but it doesn`t look
like the weather will reach criteria long enough for a large
enough area to require a red flag warning.


CO...Wind Advisory from 11 AM this morning to 7 PM MDT this evening
     for COZ001-002-007-008.



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