Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 191647

Area Forecast Discussion
National Weather Service Grand Junction CO
1047 AM MDT TUE JUL 19 2016

.SHORT TERM...(Today through Wednesday)
Issued at 356 AM MDT Tue Jul 19 2016

H5 00Z hand analysis shows high pressure centered over the lower
Mississippi Valley and an anomalously strong low off the left-
central coastline of NOAM. This pattern is efficiently drawing
monsoonal moisture across the Desert SW into our CWA. It takes
only a wiggle in this moist...unstable atmosphere to trigger
convection and this has been apparent during the overnight hours.
Showers and thunderstorms continue to develop and track across the
high plateaus and central mountains in the pre-dawn hours.
Regional radar/satellite imagery suggest a downturn in activity across
our southern CWA into northern AZ/NM. Water vapor imagery and
model dynamic trop progs suggest a wave lifting across this region
this morning as well as kicking off the activity along the
southern AZ/NM this morning. At least there are a few features to
key on today that should kick off more activity today in our
region. Again expect the convection to survive late into the night
but confidence very low on exactly where so low pops retained
again into the early morning hours. Both short term models are
keying in on a more distinct wave over central Chihuahua this
morning. The GFS is quicker to move this up toward the 4 Corners
late Wednesday afternoon while the NAM holds this back. Either
way expect another round of afternoon showers and thunderstorms
and pops remain high. The arrival of this wave may just determine
how much convection survives into the overnight hours.
Temperatures will remain near normal for mid July.

.LONG TERM...(Wednesday night through Monday)
Issued at 356 AM MDT Tue Jul 19 2016

Wednesday Night through Thursday: Elevated PW values of an inch
or greater with the NAM indicating up to 1.3 inches over some
areas will remain in place through Thursday. Embedded shortwaves
and perturbations in the flow will continue to move through the
region from time to time and are hard to time at this point.
Regardless, this will allow for widespread to numerous showers and
thunderstorms with some activity continuing through the overnight
hours as outflow boundaries and disturbances interact to provide
added lift with moisture and instability already in place.

Friday through Monday: By Friday, the low over the Pacific
Northwest will eject a stronger disturbance across the northern
Rockies, which turns the flow from southwest to westerly and
breaks down the ridge of high pressure over the Plains that is
allowing deeper moisture to be drawn up into the region. PW values
decrease to 0.5 inches across portions of NE Utah and NW Colorado.
The high center will reposition itself westward with drier air
moving into the Great Basin. This all leads to a downturn in storm
activity towards the coming weekend into next week. Enough
moisture will still linger south of I-70 and along the divide with
PW values of 0.75 inches or better for afternoon convection mainly
over higher terrain, although some storms could drift or form over
valleys late in the day.

Max temperatures will be cooler more towards normal values with
increased clouds and showers/storms and higher relative
humidities this week. A warmup towards above normal is expected by
the weekend into next week as a result of the drier airmass.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1044 AM MDT Tue Jul 19 2016

Moist monsoonal flow will continue to dictate shower and
thunderstorm development over eastern Utah and western Colorado
over the next 24 hours. The most probable time period for storms
will be during peak heating into the mid-evening hours. However
it is likely that some activity will survive well into the early
morning hours on Wednesday. Outflow from passing storms/showers
will also create erratic wind directions and speeds so TAF
adjustments are likely over the next 24 hours. Expect VFR to
prevail but with the moist atmosphere in place, moderate to heavy
rainfall is becoming more likely and could temporarily impact
visibility down into the IFR category.


.GJT Watches/Warnings/Advisories...


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