Area Forecast Discussion
Issued by NWS Grand Junction, CO

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606
FXUS65 KGJT 180503
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1103 PM MDT Thu Aug 17 2017

.SHORT TERM...(Tonight through Friday night)
Issued at 212 PM MDT Thu Aug 17 2017

Cumulus development is occurring over all higher terrain this
afternoon with some light showers and isolated lightning strikes
here and there as a light west to northwest flow remains over the
region. This is an overall increase in activity, as compared to
yesterday, due to a trailing shortwave skirting down over the
northern High Plains and Front Range. The 12Z GJT sounding yielded
0.61 inches of precipitable water (PW) with latest analysis
showing roughly 0.4 to 0.6 inches of PW across the region. The low
levels remain fairly dry and according to observations, it
appears that there isn`t too much precip reaching the ground with
fairly high cloud bases. Therefore, expect some gusty winds with
some light sprinkles at best, and the occasional lightning strike
or two. Convection should stay fairly anchored to the higher
terrain with pop and drop variety and most activity dying with the
sunset.

Friday looks mostly dry with high pressure sitting south of the
region. Some high terrain showers and thunderstorms are possible
in the afternoon, but expect more wind than rain with isolated to
scattered coverage at best and a relative downturn from today as
no distinct shortwave is evident during this time. Temperatures
will remain near normal with relatively cool nights continuing.

.LONG TERM...(Saturday through Thursday)
Issued at 212 PM MDT Thu Aug 17 2017

The weekend overall looks fairly dry with PW values hovering
around 0.6 inches on average as high pressure remains anchored to
the south of the region. Showers and storms are still possible
over the favored higher terrain with most valleys remaining fairly
dry.

Changes are ahead heading into next week, but models are
inconsistent with the timing of the next monsoonal moisture
increase. A trough of low pressure will move into the Pacific
Northwest and across the north on Sunday, helping to shift the
high pressure ridge eastward with a closed low developing over the
southern California coast. This helps to redirect the moisture
through Arizona and Utah in a southerly flow for a subtle increase
in moisture on Sunday. Moisture will slowly increase each day
heading into early next week as PW values rise above 0.75 inches
on Monday, with better upper level support ahead of this closed
low over the SoCal coast, as a 50 to 60 kt upper level jet streak
enters the Four Corners region and sits over Utah. As a result of
this increase in moisture, mid and high level cloud cover is also
expected to increase heading into Monday. Sticking with an overall
partly cloudy forecast to eclipse your Monday, as the timing of
this moisture moving in is still up in the air due to model
inconsistencies.

This SoCal low is expected to remain there until a stronger
trough of low pressure approaches the west coast and helps pull
this closed low through the Great Basin and across eastern Utah
and western Colorado as an open wave around the middle of next
week. Subtle timing differences, but overall expect a better
increase in shower and thunderstorm activity and coverage around
the middle of next week due to the passage of this trough, with PW
values also rising above an inch by Wednesday. Bottom line,
moisture will begin slowly increasing heading into Monday with the
deeper moisture moving over the region by the middle of next
week, leading to increasing storm chances each day. Temperatures
will largely remain near normal for this time of year through the
period, with cooler temps in clouds and showers from time to time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1101 PM MDT Thu Aug 17 2017

VFR conditions will prevail the next 24 hours with light diurnal
winds. After 19z isolated weak showers will mountains but these
will not affect any of the TAF sites.

&&

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

$$

SHORT TERM...MDA
LONG TERM...MDA
AVIATION...CC



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