Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 200506

Area Forecast Discussion
National Weather Service Grand Junction CO
1106 PM MDT TUE JUL 19 2016

.SHORT TERM...(Tonight through Wednesday Night)
Issued at 230 PM MDT Tue Jul 19 2016

In the large scale, an upper Low is spinning off the Washington-
Oregon coast and the subtropical High is on the southern plains.
This is producing a moist SW flow over the forecast area through
the work week. Precipitable water was measured at 1.22 inches on
the morning sounding, which is much above normal. Afternoon storms
are being driven by orographic lift, marginal instability, and low
shear environment. Thus storms are expected to be of the pop and
drop variety. Outflow boundary clashes will likely keep storms
going through the night. In addition a weak disturbance analyzed
over the Mogollon Rim this afternoon will move to near the Four
Corners this evening providing some additional forcing there.

Wednesday a larger wave that was in NW Chihuahua this afternoon
will work over the area. This looks to enhance thunderstorm
chances along and south of a line from Lake Powell to Steamboat
Springs. Storm coverage drops to isolated after midnight
Wednesday with no additional forcing evident.

The deep moisture, clouds, and showers bring good news and bad
news. Good, the daily temperature spread will shrink with mild
mornings and less hot afternoons. Bad, dewpoints in the 50s will
keep the afternoons feeling muggy. More good, fire concerns are

.LONG TERM...(Thursday through Tuesday)
Issued at 230 PM MDT Tue Jul 19 2016

Through Friday, the moist SW flow continues. Both the more moist
NAM and the drier GFS keep precipitable water values over one inch.
No significant disturbances are resolved for now so a broad brush
monsoonal surge forecast continues. The southern and eastern portion
of the forecast area looks to be favored for showers.

By Saturday, the Pacific NW upper Low ejects through the northern
Rockies. This turns the upper flow from SW to a drier west. The
subtropical High also expands across the southern tier of states.
All of this brings a strong drying and warming trend to the
forecast area that continues into at least next Tuesday.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1106 PM 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. An enhanced wave of showers and
thunderstorms has moved over southwest CO this evening and will
continue to track northward overnight. While this activity may
weaken somewhat as it shifts north, some showers and thunderstorms
will persist throughout the night and even into the morning
hours. Outflow from passing storms/showers may create gusty
localized outflow winds.

VFR conditions will prevail but TSRA/+TSRA will briefly produce IFR
VIS and possibly MVFR CIGS. Storm coverage will increase again
Wednesday after 18z with the best coverage expected along and south
of a line from KCNY northeast to KSBS. The strongest storms may
produce heavy rain and small hail.


.GJT Watches/Warnings/Advisories...


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