Area Forecast Discussion
Issued by NWS Grand Junction, CO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

FXUS65 KGJT 131704

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1104 AM MDT Tue Mar 13 2018

.SHORT TERM...(Today through Wednesday)
Issued at 320 AM MDT Tue Mar 13 2018

Currently some scattered mid and high level clouds out there this
morning across the north, with some light snow reported earlier
this morning at Aspen. Kept some isolated light showers in the
forecast through early morning to account for this. The low levels
are very dry so not anticipating much reaching the ground. Western
slope residents should wake up to partly to mostly sunny skies out
there as a ridge of high pressure slides over the region today.
Anticipating a dry and mild day as temperatures continue to climb,
a few degrees warmer than yesterday. Some building cumulus
expected to develop over the higher terrain this afternoon with
the heating of the day, but not expecting any precipitation with
the dry atmosphere in place. Some virga may be present over the
San Juans.

Southwest flow increases on Wednesday with H7 temps in the 2C to
6C range and H7 winds increasing to 30 to 40 kts over eastern
Utah and portions of western Colorado near the CO-UT border. A
breezy to windy day is in store with sufficient mixing early
afternoon to allow temperatures to climb about 15 degrees above
normal. What does this mean for us? Well, high temperatures have
potential to reach near 70 to low 70s for the lower valleys of
west-central Colorado, east-central Utah and southeast Utah. Some
places could see near record highs on Wednesday. A fly in the
ointment so to speak that would be a detriment to how strong the
winds are and how high the temperatures reach, is the timing of
the mid and high level cloud cover moving in from the west.
Current projections look like the cloud cover will hold off until
late afternoon and evening, which would give enough sunlight and
daytime heating to allow winds to mix to the surface and temps to
warm before the clouds roll in ahead of the next weather maker
discussed below. Precipitable water values will increase to
between 0.5 and 0.6 inches across eastern Utah and extreme western
Colorado late Wednesday afternoon, allowing for the development
of isolated to scattered thunderstorms mainly over the higher
terrain, before potentially spreading into some valleys by
Wednesday evening. Expect virga initially late Wednesday afternoon
with gusty winds the primary concern before the low levels
moisten Wednesday evening. Winds overall are expected to remain
below advisory criteria but could be close in some areas. The
presence of virga could potentially drive winds above that
threshold, which is gusts of 45 mph or greater. This will be
something to monitor whether wind highlites may be needed.

.LONG TERM...(Wednesday night through Monday)
Issued at 320 AM MDT Tue Mar 13 2018

A large amplitude trough moving onshore Wednesday will increase
available moisture in unseasonably warm southwest flow beginning
late Wednesday. The troughiness over the western US will be
kicking a few disturbances through the forecast area Wednesday
night and Thursday as the trough remains nearly stationary. Cooler
air aloft moving in from the west will gradually drop temps
overnight Wednesday, though southwest flow will continue
overnight. The true surface cold front with this system will
remain north of eastern Utah and Colorado, with winds not
expected to shift much with the cooler air advecting in from the
west initially. Precip is expected to be of a convective nature
Wednesday night so will likely be scattered and favoring higher
terrain across eastern Utah and parts of western Colorado. Snow
level Wednesday night will likely be above 10,000 ft, then
dropping to or slightly below 10,000 ft by Thursday morning. The
focus of precipitation shifts eastward slightly on Thursday as
energy focuses showery activity over western Colorado and a
stronger and more defined cold front with a wind shift to
westerly/northwesterly flow by late in the day Thursday. Some
areas could see some good wetting rains out of this active
weather period, but it`s nearly impossible to pinpoint where that
will be. Forecast models differ quite a bit on how "cold" this
second system is on Thursday, with H7 temps somewhere between -2C
and -7C on the backside of the front. The NAM is quite a bit
drier than the other models, but may not be unrealistic since
both Wednesday and Thursday should be showery.

Looks like there will be a break in the weather on Friday and
into early Saturday as the parent trough and closed low continues
to rotate over the western US. More scattered showers may roll
through late in the weekend with conditions potentially drying out
for a few days early next week.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1045 AM MDT Tue Mar 13 2018

VFR conditions are expected through the period. Expect some mid
and high level clouds to pass from west to east today. Winds will
be generally light out of the west before southwesterly flow
increases on Wednesday afternoon.




AVIATION...MAC is the U.S. government's official web portal to all federal, state and local government web resources and services.