Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 230007
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
607 PM MDT THU SEP 22 2016

.UPDATE...
Issued at 600 PM MDT Thu Sep 22 2016

Big storm impacts continue. So far the largest impacts are the
heavy rain in NE Utah. Vernal has reported 2.26 inches before 6
PM, with 3 inches or more in Roosevelt. Uintah County will likely
see rainfall through about 9PM, so a Flash Flood Warning was
issued there.

Also the short term and synoptic models are capturing the storm
enhancement along the Lake Powell- Colorado River area, then track
this enhancement slowly to the east over the course of the
evening. Heavy rainfall with runoff issues are possible in the
Canyonlands and Arches National Parks and Moab area. So have
issued a Flash Flood Watch valid until 3 AM there. The enhanced
showers will march east through the night into far western
Colorado after midnight then into the eastern zones Friday
morning.

Another area is the Pagosa Springs area that has had training
storms dumping heavy showers there. We are watching that area for
potential flash flooding, mainly to the south and west of Pagosa.

Wind gusts so far have generally been in the 40 mph range for
western valleys, with some gusts to 60 in the mountains. But any
thunderstorm enhanced wind could be much stronger as the storms
are moving to the NE at 45 to 55 mph. So the High Wind Warning
still looks like a valid product.

Remember our radar is down and your eyes on the ground can help us
warn on the impacts of this storm. Please send any reports to
wxgjt@noaa.gov or post them on our Facebook page. Thanks!

&&

.SHORT TERM...(Tonight through Friday night)
Issued at 351 PM MDT Thu Sep 22 2016

Winds have increased today as the advertised storm system
approaches from the west. South-southwest wind gusts to 35-45 mph
and greater have been reported. In addition, one large band of
precipitation has been stretched from roughly central Arizona
across central to northeast UT and into central WY today. This
band has been relatively stationary since early this morning with
heavy rain reported in NE UT, where flood highlights are in
effect. This band is associated with the position of the upper
level jet on the upstream side of the low pressure trough now in
the Great Basin. The low will shift east overnight pushing a cold
front ahead of it. This front is progged to reach our western edge
mid-late evening and far western CO around midnight. It will then
proceed across the remainder of the area overnight. As the front
nears, convective showers and thunderstorms will become more
numerous and will enhance the already strong wind gusts. We could
see some wild conditions at times tonight as the front tracks
across the area. Temperatures will remain on the mild side due to
the unsettled nature of the air mass. However, over the higher
elevations snow will be expected above 10000-11000 feet elevation,
and the snow level will be pushed lower at times in convective
showers. Small hail, graupel and snow pellets will be possible.

The upper low pressure center will move into central UT by
daybreak, then will shift to the northeast and will reach west
central WY by the late afternoon. As a result conditions will
remain unsettled favoring the northern half in better proximity to
the low. Southwest winds will again strengthen during the
afternoon, but will not be as strong as today. Temperatures will
be significantly cooler with highs as much as 20 degrees less than
today`s. The higher elevations of the north could continue to see
snow showers at times. However there will be little to no
accumulations as the ground remains warm.

The flow will become west overnight with the chance for showers
continuing over the far north as another lobe rotates around the
low. Again much cooler nighttime lows are expected. A couple
inches of snow will be possible by morning over the Eastern Uinta
Mountains, and the Park and Elkhead ranges and Flat Tops. However
the air mass holds onto enough moisture to somewhat inhibit the
radiational cooling. The drier areas will be in the south where a
few southwest CO valley locations may fall below freezing.

.LONG TERM...(Saturday through Thursday)
Issued at 351 PM MDT Thu Sep 22 2016

Unsettled conditions will persist into Saturday as general
troughiness remains over the central Rockies. The trough axis is
progged to shift east of the Divide in the afternoon for a
downturn in activity. Temperatures will remain well below normal
for this time of year.

A drying and warming trend will get underway on Sunday as the low
moves into the northern plains and high pressure develops along
the California coast. Dry and warmer conditions will then persist
through the remainder of the forecast period as the large scale
pattern slowly evolves. Near, to a little above normal
temperatures may develop by midweek. With time, the low will shift
into the Great Lakes region as the high pressure ridge weakens
somewhat as it moves eastward over our area. By midweek models
indicate another tropical disturbance moving north along the Baja
Peninsula and a low pressure system developing over the Pacific
Northwest. If these come together, we could see another round of
wet weather, but if this verifies it will be beyond the 7-day
long term period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 351 PM MDT Thu Sep 22 2016

The stream of deep moisture continues to be directed from the
Desert SW into NE Utah where moderate to heavy rainfall has
dropped KVEL into LIFR conditions at times. This line of
moisture/showers will slowly begin to migrate eastward early this
evening while additional showers and storms begin to form over the
terrain of western Colorado. KVEL and possibly KCNY will have the
highest probability of seeing aviation impacts of mvfr or lower
conditions until around 03z. Confidence is lower at other sites.
However wind gusts over 35 kts will be likely at all the forecast
sites this afternoon ahead of an approaching cold front. Gusts as
high as 55 kts will be possible, especially when accompanied by
thunderstorms. The front pushes across the region overnight and
impacts to flight conditions are likely. Conditions will remain
unsettled on Friday with gusty winds and a chance of showers and
thunderstorms in the afternoon. However the winds are not
expected to be as strong as today`s.


&&

.GJT Watches/Warnings/Advisories...
CO...Wind Advisory until 5 AM MDT Friday for COZ003-004-009-010-012-
     013-017>019.

     High Wind Warning until 5 AM MDT Friday for COZ001-002-006-007-
     011-020>023.

     High Wind Warning until 6 AM MDT Friday for COZ008.

UT...Wind Advisory until 5 AM MDT Friday for UTZ023-025-028.

     Flash Flood Watch until 3 AM MDT Friday for UTZ025-027-029.

     High Wind Warning until 5 AM MDT Friday for UTZ022-024-027-029.

&&

$$

UPDATE...JOE
SHORT TERM...EH
LONG TERM...EH
AVIATION...EH


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