Area Forecast Discussion
Issued by NWS Grand Junction, CO

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547
FXUS65 KGJT 162012
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
212 PM MDT Mon Oct 16 2017

.SHORT TERM...(Tonight through Tuesday night)
Issued at 143 PM MDT Mon Oct 16 2017

High pressure remains to the south of the Four Corners this Monday
afternoon. Temperatures have struggled somewhat as inversions have
been slow to mix out this afternoon. Expecting highs this
afternoon to end up near seasonal averages (67 in GJT) with light
winds and mostly clear skies. With the ridge of high pressure
barely moving on Tuesday, a nearly identical forecast is expected.
Overnight low temperatures have been adjusted downward in this
forecast package based on a consensus of MET/MAV and ECMWF
ensemble guidance.

.LONG TERM...(Wednesday through Monday)
Issued at 143 PM MDT Mon Oct 16 2017

The long term forecast remains fairly straightforward this
afternoon. The ridge of high pressure will slowly push eastward on
Wednesday. The GFS is picking up on a weak system moving over top
of the ridge by Wednesday evening, spreading a bit of cloud cover
over the San Juans overnight into Thursday. Precipitation will be
hard to come by with this system as low levels remain dry, however
both the GFS and ECMWF do indicate the possibility for some trace
snowfall amounts in the higher terrain on Thursday. PoPs in this
forecast package reflect the chance for very light precip on the
highest San Juan peaks during this period. This system eventually
absorbs into the mean longwave trough moving into the western
CONUS later Thursday evening.

By Friday, winds finally increase over eastern Utah and western
Colorado as the gradient tightens aloft. An increase in mid-level
moisture headed southeastward with the trough will result in a
thickening cirrus deck on Friday, with some convective cloud cover
developing by mid- afternoon. Timing the onset of precipitation
remains the primary forecast challenge this afternoon. GFS/GEM
remain ahead of the ECMWF by 6 hours or so per 12z runs today,
indicating the potential for some afternoon showers whereas the
ECMWF remains dry until after dark. The combination of a quick-
moving system, lack of a strong moisture connection, and
relatively high snow levels will result in only nuisance snowfall
accumulations in the central and northern mountains Friday night through
Saturday. In fact, guidance is in relatively good agreement
showing precipitation coming to an end along the Continental
Divide shortly after noon. Beyond Saturday, northwesterly flow
returns to the Four Corners with dry and tranquil weather for the
end of the weekend and early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1131 AM MDT Mon Oct 16 2017

VFR conditions will prevail for the next 24 hours at all TAF sites
and across all of eastern UT and western CO under mostly clear
skies and light diurnal winds.


&&

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

$$

SHORT TERM...MAC
LONG TERM...MAC
AVIATION...TGJT



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