Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 170430
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1030 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 06Z TAFS through 06Z Tuesday night)
Issued at 1030 PM MDT Mon Oct 16 2017

VFR conditions and light diurnally driven winds are expected
through the next 24 hours.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...MAC
LONG TERM...MAC
AVIATION...NL



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