Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 031754

Area Forecast Discussion
National Weather Service Grand Junction CO
1054 AM MST Wed Mar 3 2021

.SHORT TERM...(Today through Thursday night)
Issued at 542 AM MST Wed Mar 3 2021

Infrared satellite imagery depicts a mainly clear sky early this
morning with just a few passing thin cirrus clouds across
northeast Utah and western Colorado. Today will feature an early
spring preview with a mostly sunny sky and high temperatures
climbing 5 to 10 degrees above normal. Given very dry antecedent
conditions and a strengthening March sun angle, bumped temps up a
couple of degrees to account for efficient diabatic heating. As
it stands, Grand Junction has very good odds of cracking the
60-degree mark for the first time in 2021.

Changes begin to take place tonight as a closed mid-level low
currently off the coast of southern California lifts northeast
into the Great Basin and Four Corners. Latest model guidance
continues to be impressive with the QG forcing in play as
diffluence and the left exit region of a 125kt 250mb jet
contribute to strong large scale lift across eastern Utah and
western Colorado. Additionally, moisture will be plentiful with
this system and this is highlighted by PWATS approaching 200-250%
of normal. Despite the fast forward speed, think the stout
dynamics and moisture will lead to appreciable (and much needed!)
precipitation for a large portion of the forecast area.

Clouds increase through the night with precipitation breaking out
in southeast Utah and southwest Colorado towards midnight.
Precipitation will fill in and gradually spread northward,
encompassing most of the CWA by daybreak on Thursday. As has been
alluded to in previous discussions, there just isn`t much cold air
for this system to work with other than what is dynamically driven
by the cold pool associated with the upper level low. As such,
this will be elevation dependent storm with p-types of rain in the
lower valleys and deserts and snow in the mountains (mainly above
7-8kft). Deep southwest flow will favor southwest facing aspects
and the San Juan range in particular. Snow accumulations remain on
track with 5-10 inches expected and locally higher amounts
possible in the highest elevations. In collaboration with
surrounding WFOs, decided to hoist a Winter Weather Advisory for
the southwest San Juan mountains from 11 PM MST tonight until 5 PM
MST on Friday. The central mountains nearest to the Continental
Divide were also considered for an advisory, but believe snowfall
amounts will fall just short. A few inches of snow can also be
expected in the northern mountains, but impacts will be minimal.

Widespread showers will gradually become more convective and
scattered Thursday afternoon as the upper low moves overhead. In
its wake, drier air and subsidence will quickly follow and shut
most precipitation off by Thursday evening. Skies clear Thursday
night with a return to tranquil weather.

Given clouds and precipitation, high temperatures Thursday will
be quite a bit cooler compared to today and will run closer to, if
not a few degrees below normal.

.LONG TERM...(Friday through Tuesday)
Issued at 542 AM MST Wed Mar 3 2021

High pressure builds back in on Friday on the backside of the trough
that brought the precip Thursday. While winds will be from the east,
which usually brings some cooler temps, plenty of sunshine is
expected that will allow high temperatures to rebound to more normal
values by the afternoon.

The ridge axis will pass overhead late Friday into Saturday causing
winds to become southerly. Model guidance has been steadfast in
bringing much warmer temperatures to the region for the weekend
thanks to this stronger warm air advection. Saturday will be warm
but both Sunday and Monday look to be the warmest days with highs
about 10 degrees above climatological norms. Deterministic models
also indicating a weak shortwave moving through Saturday evening
through Sunday morning. Ahead of this wave, the gradient looks to
tighten some so expect some afternoon breezes during the day
Saturday. The EC brings more moisture with the wave while the GFS
keeps all moisture to our north...but saying `more moisture` is a
bit of a misnomer though as .2 inches of QPF isn`t much at all.
Either way, by noon Sunday, a shallow, transitory ridge moves over
the CWA keeping warm temps in place with partly cloudy skies

By Monday evening, a deeper, longwave trough comes ashore across the
west coast and by Tuesday morning the trough axis will be `just` to
our west. Some spotty showers are possible through about noon and
then as the trough axis pushes through, an increase in precip is
expected. Remember, we`re talking 6 to 7 days out so plenty of time
for this solution to change. At least there`s some hope for more
precip after a bit of a dry period.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1044 AM MST Wed Mar 3 2021

VFR conditions will prevail for much of the day with mostly sunny
skies. Clouds increase from the southwest late this evening with
showers increasing after 06Z Thursday among the southern TAF
sites. Showers spread northward affecting the central areas after
10Z. Lower valleys should see rain with snow in the higher
elevations and a mix in the southern valleys. Anticipate ILS
breakpoints to be met with low CIGS in any showers and brief
MVFR/IFR conditions at the higher elevation sites and southern


CO...Winter Weather Advisory from 11 PM this evening to 5 PM MST
     Thursday for COZ019.



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