518
FXUS65 KGJT 181727
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1127 AM MDT Fri Apr 18 2025

.KEY MESSAGES...

- The focus for heavy precipitation today will be the southern
  and central mountains and adjacent valleys, with lower
  elevation rain and higher elevation snow expected.

- Afternoon convective showers will bring another round of
  valley rain and mountain snow, as well a few rumbles of
  thunder, to the remainder of eastern Utah and western
  Colorado.

- With much colder temperatures expected the next few days,
  there is a high (>75%) chance of below freezing temperatures
  for the southern valleys, and a moderate (>50%) chance for the
  central Colorado valleys.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 322 AM MDT Fri Apr 18 2025

The cold front has worked its way through eastern Utah and much of
western Colorado over the last several hours, bringing heavy valley
rain and heavy mountain snow. Roads at pass level are snow covered,
and will continue to accumulate snow through the morning commute
hours, so be sure to take it easy and be prepared for difficult and
slow travel this morning. The southwest Colorado valleys have
remained under a dry slot the last few hours, with lingering
southwesterly winds and mostly clear skies. This should change by
daybreak as the frontal band finally moves in and even stalls out
for several hours this afternoon and into the evening as the base of
the trough swings through the Four Corners. Cold air aloft behind
the cold front will lead to increased instability this afternoon
over the rest of eastern Utah and western Colorado, leading to
widespread rain and snow showers. This convective activity combined
with the already much colder temperatures...5-10 degrees below
normal...will lead to some flakes potentially reach valley floors
this morning, and some mountain corridors picking up a bit of slush.
The highest elevations are still on track to see 6-12 inches out of
this system by Sunday, with locally higher amounts possible on
favored slopes. Winter Weather Advisories still remain in effect
through tonight. At this point, the focus of precipitation shifts
southward as the low swings into the Four Corners, allowing
highlights for the northern mountains to drop off. The next round of
Winter Weather Advisories to drop off will be for the La Sals,
Abajos, and Uncompahgre Plateau as the low starts to move eastward
and precipitation tapers off from west to east. Finally, the Winter
Weather Advisories for the central and southern mountains will drop
off tomorrow evening as the low finally tracks east of the Divide.
With the track of the low not only keeping precipitation going over
the southern San Juans the longest, it also keeps flow generally
southern to southwesterly. This is the most favorable direction for
orographic enhancement of precipitation in this area, leading to
some higher snow totals across the peaks. While a generally 6-12
inches is still expected, some areas at the highest elevations along
the spine of the Divide in the vicinity of Wolf Creek Pass could see
snow totals in excess of 16 inches by Sunday morning.

Most of eastern Utah and western Colorado can expect to see clearing
skies tomorrow night, which will favor strong radiational cooling.
With an already unseasonably cold airmass in place, this brings a
freeze risk to areas where spring growing is already well underway.
Guidance is very keen on a freeze for the Paradox Valley and the
southwest Colorado valleys tonight into tomorrow morning, with a 70-
100% chance of temperatures below 32F, and a 40-60% chance of
temperatures below 28F. As such, went ahead and upgraded the Freeze
Watches for these areas to Freeze Warnings from midnight tonight to
9 AM tomorrow morning. Guidance is less confident regarding the
Grand Valley and Central Gunnison/Uncompahgre River Basin.
Probabilities for temperatures below 32F for the Central
Gunnison/Uncompahgre River Basin is 40-60%, depending on what
guidance one looks at, with just 20-30% probability of temperatures
dropping below 28F. Probabilities are even lower in both categories
for the Grand Valley. As such, have elected to leave the Freeze
Watch in place, and allow the day crew to reevaluate this afternoon
with fresher model guidance. The Freeze Watches for all these zones
as well as Southeast Utah remains in effect for tomorrow night into
Sunday morning. With higher pressure building in and clear, dry
conditions expected, probabilistic guidance is already giving better
chances of freezing temperatures Saturday night into Sunday, even
across the Grand Valley and the Central Gunnison/Uncompahgre River
Basin. So stay tuned.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 322 AM MDT Fri Apr 18 2025

By Sunday morning this trough will be well onto the Plains and the
pattern through the remainder of the forecast will be much less
amplified across the West. This in general means a drier and warmer
outlook through next week as highs settle around 5 to 10 degrees
above normal. There will be a front meandering south of the Wyoming
border at times as a series of system move across the Northern
Rockies and Plains. The will brings some lower chances of
shower/thundestorms activity across the northern part of the CWA
through the week. QPF amounts from Sunday onwards are the highest
over the spine of the northern mountains...topping out at near 1/3
of an inch for the period. The overnight temperatures will remain a
bit cool over the southern valleys and freeze headlines may continue
to be warranted. It doesn`t look overly windy through this period
either but warm afternoons are likely to promote some deeper mixing
and lead to at least some localized areas of critical fire weather
conditions. This may become more of a concern by next weekend as
another deep trough is favored over the West by most models. As this
trough moves inland the southerly flow should tighten over the
Intermountain West and lead to windier conditions.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1121 AM MDT Fri Apr 18 2025

Scattered showers are causing IFR/MVFR conditions at several
sites. As we warm and this storm fills with convective showers
the forecast will become a bit more tricky with exact conditions
and timing so expect amendments through the day. The storm
drops through the southern area late tonight into Saturday
leaving most of the concern in this area. However lingering
moisture could keep low cigs as a threat in many areas.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory until midnight MDT tonight for COZ004-
     009-010-013.
     Freeze Watch from late tonight through Saturday morning for
     COZ006-011.
     Freeze Watch from late Saturday night through Sunday morning
     for COZ006-011-020>022.
     Winter Weather Advisory until 6 PM MDT Saturday for COZ012-018-
     019.
     Winter Weather Advisory until noon MDT Saturday for COZ017.
     Freeze Warning from midnight tonight to 9 AM MDT Saturday for
     COZ020>022.
UT...Freeze Watch from late Saturday night through Sunday morning
     for UTZ022.
     Winter Weather Advisory until noon MDT Saturday for UTZ028.

&&

$$

SHORT TERM...BGB
LONG TERM...15
AVIATION...TGJT