Debris Flow in Colorado, September 6, 2018

Area Forecast Discussion
National Weather Service Grand Junction CO
1146 AM MDT Thu Sep 6 2018

.SHORT TERM...(Today through Friday)
Issued at 319 AM MDT Thu Sep 6 2018

Early morning convection once again blossoming over our CWA. Today
it is in the SW Colorado where isentropic upglide and moisture
transport was occurring due to surface high pressure backing
Westward and undercutting mid level SW flow. Instability is being
released by this weak low level lift as well as an upper level
wind max that models all have been tracking well. This convection
should continue to drift northeast across SW Colorado through the
mid morning hours. After this we should see storms mainly form
over the higher terrain similar to days past as PWAT remains AOA
3/4 of an inch. The stalled trough over us the past few days will
be transitioning to the east through the day as a stronger kicker
system edges closer to the NOAM Pacific coastline. High pressure
will be will be building into the SW CONUS and nosing into the
Central Rockies ahead of the upstream trough. This will force a
much drier and warmer airmass into the region to end out the week.
Temperatures near normal today should pop up above normal by
tomorrow and persist through much of the next 7 days. The
probability of adding to our 90 degree days here at Grand Junction
looks to be high.

.LONG TERM...(Friday night through Wednesday)
Issued at 319 AM MDT Thu Sep 6 2018

A weak transitory ridge forms over the region Friday night but is
rapidly quashed by a low amplitude mid-level trough sweeping
across the northern Rockies during the day on Saturday. Regardless,
drier air moving into the area in weak northwest flow is indicated
to result in a significant reduction in diurnal moist convection
during the afternoon and evening. This activity will be largely
confined to the mountains in general with the Continental Divide
ranges favored. EC and GFS hint at a slight uptick in shower and
thunderstorm activity Sunday in response to a very shallow
shortwave brushing the northern reaches of the forecast area.
Confidence in this occurrence is low. Dry zonal flow will result
in similarly unimpressive convective activity Monday. Flow will
shift to the southwest Tuesday and Wednesday as a low deepens
over the Pacific Northwest, but moisture remains limited so
showers and thunderstorms should be few and far between.
Meanwhile, expect temperatures to warm in this regime with highs
and lows running 3 to 5 degrees above normal.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1141 AM MDT Thu Sep 6 2018

Isolated to scattered showers will continue to fire over the
higher terrain this afternoon as showers from the morning still
are tracking through some of the valley locations. Expect gusty
outflow winds to 35 mph possible near showers with brief moderate
rain possible in the stronger storms. VFR conditions will prevail
at most TAF sites with the higher elevation sites like KTEX, KASE
and KEGE most likely to be impacted by lowered CIGS and VSBY in
storms. Storm activity should come to an end after sunset as drier
air moves in behind the passing trough. Skies are expected to
clear from the west overnight with a few clouds hanging around.

&&

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

SHORT TERM...15
LONG TERM...NL
AVIATION...MDA

Hazardous Weather Outlook
National Weather Service Grand Junction CO
409 AM MDT Thu Sep 6 2018

COZ001>014-017>023-UTZ022>025-027>029-071015-
Lower Yampa River Basin-Central Yampa River Basin-
Roan and Tavaputs Plateaus-Elkhead and Park Mountains-
Upper Yampa River Basin-Grand Valley-Debeque to Silt Corridor-
Central Colorado River Basin-Grand and Battlement Mesas-
Gore and Elk Mountains/Central Mountain Valleys-
Central Gunnison and Uncompahgre River Basin-
West Elk and Sawatch Mountains-Flat Tops-
Upper Gunnison River Valley-Uncompahgre Plateau and Dallas Divide-
Northwest San Juan Mountains-Southwest San Juan Mountains-
Paradox Valley/Lower Dolores River-
Four Corners/Upper Dolores River-Animas River Basin-
San Juan River Basin-Southeast Utah-Eastern Uinta Mountains-
Eastern Uinta Basin-Tavaputs Plateau-Arches/Grand Flat-
La Sal and Abajo Mountains-Canyonlands/Natural Bridges-
409 AM MDT Thu Sep 6 2018

This hazardous weather outlook is for eastern Utah and western
Colorado.

.DAY ONE...Today and Tonight

The higher terrain of west-central and southwest Colorado will
once again be favored for thunderstorm activity today. Occasional
lightning along with gusty outflow winds will be the primary
threats with storms through late this evening.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

There is a chance for afternoon and evening showers and
thunderstorms again on Friday but mainly limited to the mountains
closer to the Continental Divide. Drier air will return to the
region for the weekend as high pressure builds in from the West,
though a few isolated storms will be possible over the mountains
each day.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.