Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 181013

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
413 AM MDT Fri Aug 18 2017

.SHORT TERM...(Today through Saturday)
Issued at 413 AM MDT Fri Aug 18 2017

Fairly benign period of weather as weak split flow under high
pressure remains over the southwestern US. Dry conditions
anticipated today with minimal afternoon convection across NE Utah
and NW Colorado. A weak 500 mb vort max will fire off showers and
thunderstorms late in the afternoon over the San Juan Mountains and
across the southern end of the Continental Divide in Colorado.
An area of deformation looks to develop overnight tonight into
Saturday morning from west to east across southern Utah and SW
Colorado which may allow a sprinkle to continue overnight during
this time. A much stronger weather disturbance will remain well
south of the Four Corners center point Saturday with monsoonal
moisture staying in SE Arizona and SW New Mexico.

.LONG TERM...(Saturday night through Thursday)
Issued at 413 AM MDT Fri Aug 18 2017

A weak trough over the western US will begin to strengthen late day
Saturday and pull moisture into the Four Corners by Sunday morning.
There is still some discrepancy on how much moisture will reach
into eastern UT and western CO, but the general trend is for
increasing clouds late this weekend into early next week. There is
decent model consensus on a disturbance moving south to north
through the Four Corners Sunday night, so the latest forecast
keeps showers and thunderstorms going throughout the evening
Sunday. The NAM is slower to increase moisture in the Four
Corners, but the GFS, SREF and NCEP ensembles are in agreement
that the high pressure will shift to be centered over the
southcentral US by early next week. This pattern is expected to
continue throughout the week with embedded disturbances bringing
an uptick in showers and thunderstorms. I have low confidence on
the timing of these disturbances at this time due to fluctuations
in run to run solutions.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 413 AM MDT Fri Aug 18 2017

VFR conditions will prevail over the next 24 hours with light
downslope/downvalley winds becoming upslope just before 18z.
After 19z isolated weak showers will develop over the mountains
but these will not affect any of the TAF sites. The southwest CO
and southcentral CO mountains are most likely to see any action




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