373
FXUS65 KGJT 201017
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
417 AM MDT Mon May 20 2024

.KEY MESSAGES...

- Warm and windy conditions today ahead of a cold front will
  drive temperatures back above climatology and winds will gust
  30-40 mph around the region.

- Showers and thunderstorms will develop along the front today.
  Storms will be capable of strong outflows and small hail. A
  few snow showers are also expected in the mountains behind
  the front Monday evening and into Tuesday morning.

- Cooler temperatures behind the front Tuesday will keep
  afternoon highs 10 degrees below climatology. Temperatures
  return to near normal Wednesday and beyond.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 401 AM MDT Mon May 20 2024

A frontal boundary stretching northeast from the Great Basin to the
Panhandle of Nebraska marks a rather abrupt moisture gradient here
in the CWA this morning. Dewpoints are in the mid 40`s across
northwest Colorado, where light rainshowers have been observed much
of the night. The moisture/front are situated along a strong jet
streak turning the bend on the West Coast trough digging into the
Great Basin this morning. Those strong winds aloft will gradually
work their way over the Four Corners this morning and drive up wind
speeds across the CWA this afternoon ahead of the approaching
frontal boundary. The strongest winds will concentrate around the
Four Corners today where southwesterly winds around 20-25 mph with
gusts to around 35-40 mph can be expected. Held off on a wind
advisory for now, due to the lack of widespread zone coverage down
there. Forcing along the front holds across northeast UT and
northwest CO into the afternoon hours. A few showers and
thunderstorms are expected to develop this afternoon as the jet
begins to pull the front through the region. Early activity will
remain north of the Colorado River Valley, then begin to fill in
during the early evening hours as the actual front swings in
northwest to southeast. The front clears northwest Colorado by
midnight and cooler, drier air quickly puts the brakes on showers up
there. However, down south, showers and convection along the front
will keep going into the overnight hours, likely not calming down
until the early morning hours. Showers will likely hang up on the
mountains through the night Monday into Tuesday, where accumulating
snow above 10000 feet is expected thanks to the generous shot of
cold air behind this front. Tuesday, we remain under the upper level
trough as it lags the front. Gradient winds will remain blustery
behind the front. Afternoon highs on Tuesday are expected to be
nearly 20 degrees cooler. Showers and additional thunderstorms
are expected across the region Tuesday as we see a series of
shortwaves work through the upper trough during the day. Steep
lapse rates will help out with some gusty outflows and small
hail.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 401 AM MDT Mon May 20 2024

Tuesday night will finally see the axis of the prolonged trough
slide east of the Divide with subsident, dry air quickly settling in
behind it. Any lingering showers will diminish and denser cloud
cover will begin to clear under the now northwest flow aloft. This
will mean a sharp drop in temperatures compared to the last several
nights with Tuesday night`s lows trending some 10 degrees cooler. In
the wake of the cold front subfreezing temperatures will be possible
in portions of southwest and northwest Colorado, while the central
Colorado and eastern Utah valleys will stay in the upper 30s to low
40s. No freeze highlights are needed at this time since the current
forecast subfreezing temperatures correlates with our zones that do
not have vegetation susceptible to damage. A quiet day is on tap for
the Western Slope on Wednesday, though upper level flow will shift
to the west as the next trough digs into the Pacific Northwest.
Can`t rule a few afternoon storms over the higher terrain once
daytime heating kicks in but, overall, it`ll be dry area-wide
with temperatures beginning to rebound back to near normal.

Models are beginning to come into better agreement regarding the
evolution of the Pacific storm as it pushes across the Intermountain
West Wednesday night before eventually tracking through Montana and
Wyoming on Thursday as it splits off from the parent system. Flow
will once again return to the southwest across eastern Utah and
western Colorado by Wednesday evening so those overnight lows will
quickly jump back to a few degrees above normal. The base of the
northern wave looks to straddle the Wyoming / Colorado border on
Thursday so expect isolated to scattered showers and storms to
develop across northeast Utah and northwest Colorado that afternoon.
Elsewhere will remain dry but breezy as the gradient tightens with
the trough.

The secondary wave looks to cross the forecast area sometime on
Friday but there are some discrepancies regarding how far south it
will drop. Depending on when this system pushes through we could be
looking at unsettled conditions going through the weekend. But, not
locking anything in at this moment as changes can be expected under
this persistent longwave troughing pattern.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1055 PM MDT Sun May 19 2024

Isolated to scattered showers will persist tonight across the
north with gusty outflow winds of 35 to 40 kts possible. The
coverage of showers and storms will increase by 18Z Monday but
activity will remain north of I-70 through the afternoon. In
addition to strong outflow winds to 45 kts, small hail and
reductions to MVFR will be possible with convection. South of
I-70 will stay dry and breezy with gusts of 30 to 40 kts Monday
afternoon. Showers become more widespread Monday evening and
overnight as a larger system begins to push through the area.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...LTB
LONG TERM...MMS
AVIATION...TGJT