Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 161023

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
423 AM MDT Fri Mar 16 2018

.SHORT TERM...(Today through Saturday)
Issued at 423 AM MDT Fri Mar 16 2018

The latest storm is currently spinning over northwest Kansas as
lee side cyclogenesis is taking place. Earlier this morning,
satellite indicated the flow around this low was southeasterly,
creating an upslope component over the Front Range foothills and
mountains. What was evident on satellite was eroding of the cloud
layer from Steamboat down towards Eagle, which indicated
downsloping. The best ascent appears to be over Wyoming in the
wraparound flow on the northern side of the upper level low.
Current satellite trends indicate warming cloud tops over the
western slope, so this lee side cyclogenesis is taking all the
energy east with the low. Meanwhile, radar indicates scattered
showers still moving across mostly the central and northern
portions of western Colorado. These showers remain light and
webcams that we can see indicate little impact. There may be a
brief burst of moderate snow but not expecting much additional
accumulation through the rest of the morning. Therefore, in
coordination with the BOU, PUB and CYS offices, we have all
decided to cancel the remaining winter weather advisories.

Drier air moves in late this morning into the afternoon with
southwest flow returning to the region, resulting in partly to
mostly sunny skies and temperatures bouncing back to near normal
or slightly below normal values. The parent upper level low
remains over the Pacific Northwest while its child that affected
the region yesterday through this morning moves further away from
home into the Plains. Breezy conditions will ensue Friday night
into Saturday afternoon as H7 winds increase to 20 to 30 kts ahead
of the parent upper level low over the Pacific Northwest that has
decided to chase after its child. Saturday afternoon will be
fairly mild, with some building cumulus possible over the higher
terrain as lapse rates increase to 7 to 9 degrees C/km. Low levels
will be dry initially with these cumulus possibly squeezing out a
virga shower or two. Overall, the best potential for moisture and
precipitation will not move in until Saturday evening, with models
favoring eastern Utah at first. More on this storm system
discussed below in the long term section.

.LONG TERM...(Saturday night through Thursday)
Issued at 423 AM MDT Fri Mar 16 2018

The parent upper level low which has been bringing rain and snow
to the western US is considering pushing one last storm through
Utah and Colorado late Saturday and Sunday before building
slightly drier northwesterly flow into the region early next
week. Forecast models are fairly in sync on the strength, timing
and track of this system, which brings the cold front and trough
axis through the region Sunday afternoon. Precip type looks to
start off as rain in the lower valleys and snow in the mountains,
with eastern Utah being favored Sunday morning, spreading across
western Colorado Sunday afternoon. The best upper level support
and large scale ascent will occur across SE Utah and SW Colorado
as this system moves from SW to NE through the region. Rain will
changeover to snow in the lower elevations as this system moves
through Sunday afternoon, which would mean that snow accumulations
at lower elevations will be mainly on grassy surfaces, and snow
at higher elevations will likely be wet and slushy. If this system
slows down and the bulk of precip comes in late Sunday, snow
accumulations will be much higher. In any case, heavy snow is
possible across eastern Utah and western Colorado on Sunday with
the set up looking wet for the region. If traveling Sunday, you`ll
definitely want to be ready for rapidly deteriorating conditions
on the roads. Convection also appears to be a factor with this
system as lapse rates remain steep in the realm of 7 to 9 degrees
C/km, resulting in the chance for more thunderstorms as well. Hey,
it`s spring in the Rockies!

A couple of weaker weather disturbances look to roll through
in northwesterly flow early next week before transitory ridging
gives the region a break. Another round of exciting windy and
potentially wet conditions rolls in late next week. All the models
are in surprisingly good agreement with the synoptic pattern
through next week, lending to higher confidence in this wetter and
more unsettled pattern.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 423 AM MDT Fri Mar 16 2018

Some scattered light to moderate showers will linger across
portions of northwest and central Colorado through the morning
before dissipating by late morning. CIGS and VSBY could fall below
ILS breakpoints at times due to showers and potential fog.
Conditions improve after 18Z with partly to mostly sunny skies
prevailing for the rest of the day.




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