Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Junction Colorado
431 PM MST Thursday Dec 25 2014

Short term...(this evening through Friday night)
issued at 359 PM MST Thursday Dec 25 2014

Interesting storm today...a bit slower than anticipated and turned
quite convective during the late morning. The Grand Mesa is the
Winner so far with over a foot of new snow on top. With the slow-
down of the low pressure system...decided to upgrade advisories to
warnings for the Grand Mesa...central mountains...and northern mountains
left the San Juans in an advisory anticipating less wrap around
flow on Friday. The cold front associated with this system is
currently just east of the Wasatch Range. With cooler air moving
in from the west aloft...convective bands have developed and are
moving from southwest to northeast ahead of the front. This aligns
well with instability shown in the 500 mb to 300 mb potential vorticity
fields. The center of the low pressure system is still expected
to sag south to SW Colorado by noon Friday...which will help to
keep intermittent snowfall across the forecast area. As the low
drops south...prevailing wind directions at the time will change
and therefore the snowfall amounts will be rather dynamic due to
topographic influences. Wrap around moisture will be most
prevalent over the central mountains and potentially the
southcentral San Juans as well.

The closed low is expected to fall apart as it reaches the
Continental Divide and its associated trough will slowly exit to
the northeast on Friday night.

Long term...(saturday through thursday)
issued at 359 PM MST Thursday Dec 25 2014

Other than a few lingering showers in northwest flow over the
northcentral Colorado mountains...elsewhere is expected to be cold
and dry by Saturday morning. Zonal flow develops during Saturday
evening before the next system approaches the forecast area.
Precipitation is prognosticated to begin Sunday morning over NE Utah and
northwest Colorado then gradually drop down to affect the northern half
of both states. This system looks to be unique in that it is a
broad and wide trough with a multipart long lived weather system.
There hasn/T been great run to run consistency on where a closed
low may develop midweek...but the general consensus has been a
chance of snow over NE Utah and northwest Colorado on Sunday into
Monday...then the precipitation threat moves south Monday night
into Tuesday while a closed low develops somewhere from socal to
southern Nevada. This might affect southern Utah by Thursday...but
confidence is low so will have to wait and see what future model
runs hold.


Aviation...(for the 00z tafs through 00z Friday evening)
issued at 432 PM MST Thursday Dec 25 2014

Upper level low continues to slide southeast towards The Four-
Corners region. The main focus during the next few hours will be
a band of snow which is affecting cny and gjt taf sites. Expect
this activity to dissipate over the next few hours with only vcsh
continuing overnight. Snowfall will develop over the remainder of
the Colorado taf sites over the next few hours as flow becomes
more favorable. Expect snow with low ceilings/visibility for dro through
12z and through Friday afternoon for the Colorado taf sites.


Gjt watches/warnings/advisories...
Colorado...Winter Weather Advisory until 6 PM MST Friday for coz001-002-007-

Winter Weather Advisory until 3 PM MST Friday for coz006-020.

Winter Weather Advisory until midnight MST Friday night for

Winter Storm Warning until midnight MST Friday night for coz004-

Winter Weather Advisory until 5 am MST Friday for coz022.

Utah...Winter Weather Advisory until 6 PM MST Friday for utz023-025-028.

Winter Weather Advisory until 3 PM MST Friday for utz024-027-029.



Short term...jam
long term...jam

National Weather Service Glossary of Abbreviations