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000
FXUS65 KGJT 200135
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
735 PM MDT MON SEP 19 2016

.SHORT TERM...(Tonight through Tuesday night)
Issued at 335 PM MDT Mon Sep 19 2016

Mostly sunny skies will prevail for the remainder of the day as
high pressure remains in control with dry conditions. Moisture
will begin to increase from the southwest overnight into Tuesday
in the form of mid and high level clouds across the Four Corners
region, as moisture gets drawn up from Hurricane Paine which is
spinning right off the Baja Coast. Precipitable Water values
increase to a little over an inch near the Four Corners on Tuesday
with a shortwave disturbance moving across southern California
into the Four Corners region Tuesday evening, helping to pull this
moisture from Hurricane Paine northward. The focus for storms will
be across southeast Utah and southwest Colorado late Tuesday
afternoon into the evening. Decent shear exists with little
instability which may provide more organized storm activity. Heavy
rain is possible with the stronger storms.

.LONG TERM...(Wednesday through Monday)
Issued at 335 PM MDT Mon Sep 19 2016

Wednesday: Southwest flow continues on Wednesday with enough
moisture in place to get thunderstorms developing over the higher
terrain in the afternoon. Drier air works its way in towards
Wednesday evening as a strong trough of low pressure digs down the
West Coast and amplifies over the Great Basin.

Thursday into Friday: Moisture will work its way in from the west
with showers and storms developing under a strong southwest flow.
The gradient tightens with H7 winds of 30 kts from the south and
H5 winds of 40 kts from the southwest increasing to 45 kts at H7
and 60 to 80 kts at H5 by Thursday evening. The potential exists
for wind highlites on Thursday due to the tightened gradient so
this will need to be monitored. Thursday is also looking like
potential exists for some strong to severe storms, as much of the
forecast area remains in the right entrance region of a 100 kt jet
that curves cyclonically around the base of the upper level
trough that strengthens and forms a closed low over the Great
Basin. Sufficient speed and directional shear exists as well as
enough instability and forcing for more organized activity. Gusty
outflow winds, hail and heavy rain will be possible with storms
that form. This is all ahead of a strong stand up cold front that
will move through Thursday evening into Friday morning west to
east across the forecast area. The winds begin backing with height
after the cold front moves through Thursday evening into Friday
morning, as strong CAA takes place. H7 temps lower by 8 to 12
degrees from Thursday afternoon to Friday afternoon for much
cooler temperatures across the area. H7 temps will continue to
lower throughout the day on Friday as the upper level low lifts
northeast across Wyoming. H7 temps will be in the 0C to -2C range
for areas north of I-70 with snow levels lowering to 8000-9000 ft
MSL. Accumulating snow is possible above 8000 ft MSL with the
mountains of northeast Utah and northwest Colorado being the most
affected as the flow shifts around to northwest orographics from
Friday morning through Saturday morning. This may cause impacts
for travelers across these higher mountain passes so stay tuned to
the latest forecast as details come into greater focus.

Saturday afternoon through Monday: the main upper level low will
track across the northern Rockies into the northern High Plains
while the upper level trough gets stretched out across our
forecast area with a closed low splitting off the main trough and
forming over Arizona. The upper level flow will turn more
northerly Saturday afternoon and shift to an easterly flow across
our forecast area as the low pressure closes off over Arizona
underneath an upper level ridge across the west, essentially
putting an end to precipitation. The flow shifts back around to
the south by Monday with some storms possible in the afternoon
across the southern mountains. Otherwise drier conditions are in
store for Saturday afternoon through Monday with below normal
temperatures.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 735 PM MDT Mon Sep 19 2016

VFR conditions will continue through 18z Tuesday. Cloud decks will
thicken by late Tuesday morning with bases remaining above ILS
thresholds. After 18z...Scattered showers and thunderstorms will
move into southeast Utah and southwest Colorado with storms moving
northeast and into the central zones by late afternoon. The
showers may result in brief mountain obscurations. Freezing levels
will be running near mountain tops with some snow possible Tuesday
night.

&&

.FIRE WEATHER...
Issued at 335 PM MDT Mon Sep 19 2016

Further north towards the Wyoming border, low RH and gusty winds
will combine to produce areas of critical Fire Weather conditions
across northwest Colorado on Tuesday afternoon. However,
conditions do not look very widespread and more localized so did
not issue any Fire Weather highlites at this time. Winds are also
marginal in many areas as well. Moisture increase from the south
late Tuesday afternoon may also limit the duration of these Fire
Weather conditions. This is something for future shifts to
monitor.

&&

.GJT Watches/Warnings/Advisories...
CO...None.
UT...None.
&&

$$

SHORT TERM...MDA
LONG TERM...MDA
AVIATION...JDC
FIRE WEATHER...MDA