Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 181712
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1112 AM MDT Tue Jul 18 2017

.SHORT TERM...(Today through Wednesday)
Issued at 426 AM MDT Tue Jul 18 2017

Fairly active nocturnal showers are likely to survive toward
sunrise over the northwest Colorado this morning. These showers
are the result of fairly steep mid level lapse rates and moisture
gradient being enhanced by a wave lifting across S.Wyoming. Expect
a mid morning lull before convection starts to bubble again.
Models all suggest the better coverage mainly south of a line
drawn from the Gore Range in the east to the Abajos in the West.
There will be isolated storm coverage north of this line but
the drier air seen on H2O this morning will be swept across the
north and suppressing moisture toward our southern border. This
will only be temporary though as the well advertised monsoonal
push looks to start back northward overnight into Wednesday.
Convection...especially nocturnal...is never easy to pinpoint but
with good moisture transport tonight...showers should be
lingering well into the early morning hours across the 4 Corners
Region then expand in coverage over much of the CWA by early tomorrow
afternoon. Models are also picking up on a couple of features to
make this forecast interesting. First is the wave driving stronger
convection early this morning across W.New Mexico. The NAM
latched onto this a few days ago and this feature should continue
to rotate around the low into Southern Utah over the next 24 to 36
hours. The other notable feature is the dry air rotating westward
along the Red River Valley of Texas. It appears this will could
get entrained into our SE CWA as early as tomorrow afternoon and
leave a narrow band of the highest PWAT over the northern half of
the CWA. The models handling both these features a bit different
which could create a rather big discrepancy in tomorrow`s
sensible weather across the south. For now have leaned toward the
wetter solution with some reservation. Concern for heavy rain and
flooding will be there due to the wetter airmass but confidence
not there for any type of watch attm. Temperatures above normal
today...cool back tomorrow with arrival the clouds and
precipitation.

.LONG TERM...(Wednesday night through Monday)
Issued at 426 AM MDT Tue Jul 18 2017

The main high circulation will make it onto the Plains by
Wednesday afternoon leaving the more favorable southerly flow to
bring in monsoonal mositure to our CWA. Or will it? The above
mentioned dry air feature seems to continue to rotate into our CWA
Wednesday night into Thursday. Do think there should be a rather
noticeable downturn to storms in the southeast on Thursday with
the main plume of moisture moving across Central Utah into
N.Colorado. The wave entering S.Utah this afternoon will be riding
the SW flow through our CWA early in this period and would serve
to focus a heavy rain threat near this feature. This is when a
flood watch could be warranted. The thicker cloud cover is always
problematic with these monsoonal pushes...enter the drier air to
the south...and we could see conditions favorable for some
stronger storms to put down some good rain up north. A low
confidence forecast this far out for sure. We stay in the residual
monsoon moisture plume through Saturday before the westerlies
make a dip southward and push this plume eastward.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1043 AM MDT Tue Jul 18 2017

Still looks like scattered showers and thunderstorms mainly this
afternoon and evening south of a KEGE to KMTJ to KBDG line, some
with heavy rain, small hail and local MVFR cigs/vsbys. N of the
line expect some showers and thunderstorms, though less than to
the south of the line. Otherwise VFR conditions can be expected to
prevail through 18Z Wednesday, but an increase in showers and
thunderstorms thereafter from the south will increase the
likelihood of more areas with mountain obscuration and local MVFR
conditions.

&&

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

$$

SHORT TERM...15
LONG TERM...15
AVIATION...JRP



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