Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 111156
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
456 AM MST Sun Feb 11 2018

.SHORT TERM...(Today through Monday)
Issued at 455 AM MST Sun Feb 11 2018

The sky cleared out quickly after Saturday`s cold front exiting to
the southeast. Sunny skies should prevail today. Late tonight an
interesting situation develops. As a deepening trough moves into
the Great Basin a strong jet rounds the bottom of the trough and
stretches over the four corners. Moisture will advect into the
four corners from the south and southwest. Cloud bases should
lower and the lower atmosphere should moisten quickly. After
about 09z snow should be falling over the higher peaks of the San
Juans with rain or rain and snow mixed over the lower elevations
of the four corners. The uplift over the area should increase
after about 9 AM and will also spread north and west over much of
the forecast area during the afternoon and evening. 700 mb
temperatures will start on the warm side, -2 to -4 depending on
the model, then decrease late Monday afternoon and night. The
presence of a well positioned jet, warm advection and moisture
arriving from the south will bring a chance of thunderstorms
Monday afternoon, probably isolated in coverage. Believe the snow
will pile up quickly enough to justify and winter weather
advisory for the San Juans. Later shifts will have to look at the
possible need to spread the advisory north and west.

.LONG TERM...(Monday night through Saturday)
Issued at 455 AM MST Sun Feb 11 2018

Unsettled southwesterly flow will persist overhead Monday night into
Tuesday as the closed upper level low retrogrades back to south-
central California. Models have been quite heavy with QPF and, while
confidence is high for precipitation to develop over much of the
higher terrain, confidence is low for the more widespread coverage
the models seem to favor. The reason for this is the lack of upper
level support in this split flow. But, as the previous forecaster
mentioned, the San Juans and higher peaks of the Grand Mesa and West
Elks will be favored in the southwesterly flow and may have the
potential for advisory level criteria to be met. Greater detail will
be hashed out over the next few shifts and model runs.

The closed low dives even further south late Tuesday into Wednesday
with mild southwesterly flow continuing across our forecast area.
Temperatures will remain above seasonal as a result with daytime
highs climbing back into the mid 50s for the lower valleys by
Wednesday. Model discrepancies increase late Wednesday onwards as
the GFS slowly tracks the closed low across the far southwestern
CONUS/Mexico border, keeping all precipitation well to our south,
and brings another potential shortwave to the northern half of the
forecast area late in the week. Meanwhile the Euro attempts to
reintroduce the closed low into a much broader upper level trough
with significantly more moisture to work with. Needless to say,
given this wide range in potential synoptic solutions, confidence in
the forecast for the latter half of the work week is low.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 455 AM MST Sun Feb 11 2018

VFR conditions will clear skies will prevail until 09z tonight,
then a storm approaching from the southwest will bring increasing
and lowering clouds to southeast UT and southwest CO. Snow will
start falling over the higher peaks of the San Juan mountains with
rain developing at lower elevations.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory from 3 AM Monday to 6 AM MST Tuesday for
     COZ018-019.

UT...None.
&&

$$

SHORT TERM...CC
LONG TERM...MMS
AVIATION...CC



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