Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 150813

Area Forecast Discussion
National Weather Service Grand Junction CO
213 AM MDT Wed Aug 15 2018

.SHORT TERM...(Today through Thursday)
Issued at 211 AM MDT Wed Aug 15 2018

No much change expected through the short term. The ridge that has
been a fixture this summer over the Great Basin will remain there,
forcing the monsoonal plume to remain over NW Mexico and southern
Arizona. Enough of the subtropical monsoonal moisture has
filtered into and under the ridge to allow for afternoon and
evening low intensity and low areal coverage showers and
thunderstorms. That will be the case again today through
Thursday. The main focus will be over southwest CO where slightly
higher precipitable water will produce scattered showers and
thunderstorms both days. As has been the case, these storm will
form over ridges and later in the afternoon outflow boundaries and
a few storms will push off the hills and over the valleys. The
main threats from these storms will be gusty winds associated with
outflows and lightning.

.LONG TERM...(Thursday night through Tuesday)
Issued at 211 AM MDT Wed Aug 15 2018

The northern stream will remain quite active from the PacNW to
the Midwest States as a series of troughs move through this flow.
Agreement is fairly good through the weekend then begins to
separate by early next week as the last of these progressive
systems moves into the NW CONUS. This is not only late in the
forecast period but there is also a deep...anomalous trough
dropping in the the Hudson Bay area with low pressure digging into
the Upper Midwest. This bigger pattern change will probably not be
handled well for a while but higher than average heights across
the SW and West is probably a good bet. So the above normal
temperatures over our CWA should continue. PWAT at KGJT was 0.76
on the 15/00Z sounding and this is in the normal window for this
time of year and models really do not show a big jump in this
value through the end of the week. Farther toward the 4 Corners
this value is closer to an inch and again no big pushes of
moisture are indicated. This will be due to the upper level high
shifting back to the West and so recycled...indirect moisture will
be about the best we can do. This will keep some threat of
afternoon storms with gusty outflow winds still the most likely
scenario especially with upper jet support coming through on the
periphery of the passing waves to the north. Saturday could see a
slight uptick as the back side of one of these trough moves
through and brings some cooler air aloft. Behind this wave however
much drier air filters back in on Northwest flow and bring and
end to storms Sunday into early next week.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 211 AM MDT Wed Aug 15 2018

VFR conditions will prevail at all TAF sites for the next 24
hours. Isolated to scattered showers and thunderstorms will cause
local mountain top obscurations and gusty outflow winds. Widespread
wildfire smoke will limit the visibility no lower than about 7
miles except is close proximity to a fire.




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