Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Junction Colorado
959 PM MST Thursday Nov 20 2014

Short term...(tonight through Friday night)
issued at 326 PM MST Thursday Nov 20 2014

Weak trough was moving across the forecast area this afternoon with
extensive cloudiness...though some clearing is working into southeast
Utah. With some echoes on the kgjx radar...some virga or isolated
light instability snow showers over the higher terrain is not out
of the question. This will persist through evening before
diminishing as the trough/deformation axis exits to the east after

Satellite images show the next storm system moving into northern calif.
This system is expected to dive southeast on Friday. May see some
isolated light snow showers over the San Juan/Abajo/La Sal Mountains
Friday afternoon in difluent flow northeast of the upper trough.
Otherwise...partly to mostly cloudy conditions for Friday afternoon
with little change in temperatures.

Long term...(saturday through thursday)
issued at 326 PM MST Thursday Nov 20 2014

Northwest Pacific moisture is still on track to reach the forecast area
on Saturday afternoon...bringing the next winter system into the
region. Issued some winter weather watches today over northwest Colorado to
cover the highest confidence areas for heavy snow on Saturday
afternoon through Sunday afternoon. The cold front is still
expected to pass from northwest to southwest on Saturday night.
Other details are a bit different today on this storm...with the
spec humidity fields on both the GFS and NAM now indicating the
bulk of the moisture being contained to Saturday night...then more
quickly decreasing by Sunday afternoon behind the cold front
passage. The jet maximum also stays a bit further to the south yet
500 mb vorticity fields suggest the north and central mountains are still the
favored spot. Models are less enthused today to allow snow in the
Grand Valley...but the possibility of a trace of snow is not out
of the question with the nighttime timing of the precipitation. Concerned
the valley will become shadowed as winds become northwest behind
the front.

We are expecting a break in the precipitation Sunday evening
before another disturbance reaches western Colorado again on
Monday morning driven by a jet maximum. The model solutions
diverge Monday night so there is low confidence on the extended
past this timeframe. The long term blend does reflect the
potential of a storm barreling into western Colorado for
Thanksgiving day next week...though the GFS is completely out of
phase with the ec and keeps dry high pressure overhead for the
Holiday. Cannot rule out the possibility of a storm next
Thursday...but confidence is too low to get excited at this point.


Aviation...(for the 06z tafs through 06z Friday night)
issued at 947 PM MST Thursday Nov 20 2014

Widespread clouds will continue to move across eastern Utah and
western Colorado late tonight...though all taf sites are expected
to remain VFR. At times higher mountains will see obscurations and
ceilings near 3k feet from overnight. Clouds are expected to thin for a
time Friday morning before thickening again during the afternoon
and evening. However...VFR is expected to persist.


Gjt watches/warnings/advisories...
Colorado...Winter Storm Watch from Saturday afternoon through Sunday
afternoon for coz004-005-009-010-012-013.

Winter Storm Watch from Saturday afternoon through Sunday
morning for coz002.



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

National Weather Service Glossary of Abbreviations