154
FXUS65 KGJT 210948
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
248 AM MST Thu Nov 21 2024

.KEY MESSAGES...

- High pressure remains in control heading into Saturday with
  partly cloudy skies expected. Warm temperatures continue.

- Snow returns late Saturday night as an Atmospheric River sets
  up across the area. This AR may persist through Wednesday
  bringing periods of heavy snow to the mountains.

- If you`re planning on travelling during Thanksgiving week,
  especially over any mountain passes, please pay close
  attention to the latest forecasts as amounts and timing will
  likely fluctuate over the coming days.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 200 AM MST Thu Nov 21 2024

The presence of an upper-level ridge and dry air has kept skies
mostly clear. However, high-level cloud coverage will increase
throughout the day. High-level clouds are expected on Friday as
well, particularly in the northern portion of our CWA.

Warm air advection associated with the upper-level ridge will
continue to raise temperatures in our region through the short term.
High and low temperatures are expected to be as much as 5-10
degrees above average for much of the area.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 200 AM MST Thu Nov 21 2024

A low amplitude ridge axis that has been overhead the last few
days will start moving eastward as a period of unsettled weather
begins to setup. Saturday will bring increasing clouds and with
southwesterly flow over the area, we can expect another day
with warm temperatures. Further out west, a strong jet streak
will be rounding the base of a deep area of low pressure just
off the Pacific coast. This jet streak will tap into Pacific
moisture and start advecting it into the region causing an
Atmospheric River to setup. Incidentally, this is the same area
of low pressure that brought hurricane force winds to the PacNW
on Tuesday.

Moisture will reach our CWA as soon as Saturday night though
precip won`t start until a weak shortwave works on said moisture
Sunday morning. This first round of precip will bring some snow
to the northern and central mountains and Flat Tops but will
start waning Sunday night into early Monday morning. No need to
worry though as the jet stream becomes zonal over the area and
stretches from the West Coast to the central Plains. This
placement will allow the AR event to continue and keep moisture
advecting across the Intermountain West...through Wednesday
morning. As pieces of energy move through the mean flow, periods
of heavier precip will be possible. Ensembles and the
deterministic GFS and EC are in better alignment at the
beginning of this period with heavier precip getting going
around noon Monday...possibly continuing through Wednesday
evening, if not a bit beyond. Just looking at that timeframe,
snowfall amounts for all CO mountains look to be on the order of
a foot with some spots possibly reaching nearly 2 feet of new
snow. Most valley locations will likely be too warm for snow
accumulation except for higher elevation valleys...especially
heading up to Vail Pass. This will likely be a prolonged event
so if you`re planning on travelling during Thanksgiving week,
especially over any mountain passes, please pay close attention
to the latest forecasts as amounts and timing will likely
fluctuate over the coming days. Of note, latest AR forecasts are
beginning to shift the deepest moisture a little further
south and if this trend continues, the current forecast might be
overdoing things a bit.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 936 PM MST Wed Nov 20 2024

VFR conditions will prevail over the next 24 hours with
generally light, terrain driven winds as the region sits
underneath a ridge of high pressure. The more exposed KHDN
though will be subject to enhanced drainage winds from the east
overnight. This ridge will be "dirty" with some scattered high
cirrus working over the top through Thursday afternoon and
evening.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...GF
LONG TERM...TGR
AVIATION...TGJT