Area Forecast Discussion
Issued by NWS Grand Junction, CO

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863
FXUS65 KGJT 101753
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1153 AM MDT Sat Apr 10 2021

.SHORT TERM...(Today through Sunday)
Issued at 343 AM MDT Sat Apr 10 2021

The yo-yo spring forecast of fire-and-ice continues through the
next 48 hours. Clear skies, dry conditions and cold air advection
streaming across the region maintains this morning`s brisk
forecast of subfreezing temperatures across higher terrain and
a few valleys. Current freeze highlights are on tack for the
Central Gunny and Unc River Basins, where current temps have
already dipped below freezing along the US-50 corridor.

The temperature roller coaster swings back uphill today with
highs climbing roughly ten degrees warmer. Very dry conditions
linger in the wake of yesterday`s system, leaving dew points in
the single digits to low teens for much of the region. This brings
RH levels back down to single digits this afternoon which, when
combined with sunny skies, will result in a deep mixing layer
redeveloping during peak heating. Expect gusty winds this
afternoon, with strongest gusts focused over NE Utah and
NW Colorado. The next PacNW system diving across the Northern
Rockies will tighten pressure gradients across the northern tier
this afternoon. Red Flag conditions redevelop across these regions
as diurnal mixing transports stronger winds down to the surface.
Have expanded the current highlights to include Utah fire weather
zones 486 and 487, where fuels are critical.

The upswing in temperatures will moderate lows tonight, so no
concern for freeze highlights across crop sensitive valley
floors, attm. The southern two-thirds of the region will notice
very little change in temperature forecasts for Sunday. However,
the PacNW trough clipping the WY border will drive a cold front
across northern zones on Sunday. As a result, high temperatures
drop 5 to 10 degrees lower for areas north of the I-70 corridor.
The clipper will, however, tighten the pressure gradient across
the entire Western Slope leading to strong gusts region- wide
through Sunday evening. Highest confidence in winds reaching red
flag criteria is concentrated over southwest Colorado, where
watches have been upgraded to warnings. Spotty critical conditions
are likely across central valleys. However, have neglected to
expand Sunday`s products due to marginal coverage, temporally and
spatially.

Passing cold front Sunday will allow for subfreezing temps Sunday
night, mainly across NE Utah and NW CO. Therefore, a Freeze Watch has
been added for the Uinta Basin for Sunday night into Monday.

.LONG TERM...(Sunday night through Friday)
Issued at 343 AM MDT Sat Apr 10 2021

Prevailing northwest winds shift to a westerly flow on Monday as the
polar jet digs southward over the Pacific Northwest during the day.
The dry cold front which moved southward across the region on Sunday
becomes stationary over the southernmost portions of the forecast
area. Enhanced flow aloft ahead of the system combined with deep
mixing may again generate enough wind along the frontal boundary to
bring another round of critical fire weather conditions to the Four
Corners region Monday afternoon/evening.

The jet over the northwest mentioned earlier is expected to carve
out a mid-level low pressure system over the northern Great Basin
Monday night into Tuesday. As mentioned in previous discussions this
feature will generate periods of precipitation which will impact the
region from Monday night through Friday. Model differences persisted
with the 00Z cycle and GFS remained the most aggressive with
precipitation coverage and intensity followed by the Canadian then
the ECMWF. Understandably, details with respect to timing and
intensity of precipitation. As a result, snow accumulations will be
largely confined to areas above 9,000 feet with mainly rain below
8,500 feet. Looking at a breakout of snowfall over the period,
accumulations not all that impressive in any 24 hour period, so
unclear if highlights will be needed with this event, but time will
tell.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1151 AM MDT Sat Apr 10 2021

VFR conditions will prevail today with clear skies. Westerly winds
will increase during the afternoon and may become gusty at
southern and western terminals. Expect mainly clear skies
overnight.

&&

.FIRE WEATHER...
Issued at 343 AM MDT Sat Apr 10 2021

An approaching system from the northwest will bring another round
of gusty winds this afternoon. Very dry conditions and a fuel
status upgrade to critical across NE Utah have supported the
decision to expand current highlights to include UT fire zones
486 and 487, in addition to current RFWs for CO zones 200 and 202.
On the backside of the system, gusty winds materialize across the
southern zones, namely CO fire zones 207 and 295 below 8000 feet.
Watches have been upgraded to a Warning through Sunday evening
for these zones. Localized critical conditions will likely be met
across central valley zones, however confidence in coverage is
just not quite there to include in RFWs at this time.

Moisture returning to the region is promising early next week.
Unfortunately, dry conditions preceding the next system may
return fire weather concerns Monday, and likely linger across the
Four Corners region which appears more likely to see a
continuation of dry and winds conditions rather than wetting rain.
However, some lower elevation areas near the Wyoming border may
see wetting rainfall reduce the elevated fire weather threat.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning until 9 PM MDT this evening for COZ200-202.

     Red Flag Warning from noon to 8 PM MDT Sunday for COZ207-295.

UT...Red Flag Warning until 9 PM MDT this evening for UTZ486-487.

     Freeze Watch from late Sunday night through Monday morning for
     UTZ024.

&&

$$

SHORT TERM...ERW
LONG TERM...NL
AVIATION...MAC
FIRE WEATHER...TGJT



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