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Area forecast discussion 
National Weather Service Grand Junction Colorado
458 PM MDT Friday Oct 24 2014

Short term...(tonight through Saturday night)
issued at 324 PM MDT Friday Oct 24 2014

Sunny and mild conditions continued across the forecast area this
afternoon as the region languished under a ridge of high pressure
aloft. A trough approaching the West Coast will force the ridge
axis east overnight with flow aloft shifting to the southwest in
response. Very little moisture within the southwesterlies so skies
will remain clear overnight and into Saturday. Temperatures aloft
cool just a bit as the trough axis moves east...but deep mixing
will ensure temperatures remain unseasonably warm. In fact
..guidance indicated that highs will be near record levels
Saturday afternoon. Clouds will increase Saturday night as the
eastern Pacific trough sweeps over the western Great Basin. A weak
surge of moisture ahead of this system may generate a few light
showers over the higher terrain after midnight.

Overnight lows will be near normal tonight becoming a bit milder
Saturday night as clouds increase over the region. As mentioned
above...Saturday will be unseasonably warm.

Long term...(sunday through friday)
issued at 324 PM MDT Friday Oct 24 2014

The ridge will continue to break down on Sunday under the strain of
the trough moving off the left coast toward the Great Basin. On the
satellite scope this afternoon the ridge is now expanding across the
west but the more interesting features lie upstream. A robust
northern stream polar jet is reforming on the downside of eastern
Pacific energy and tapping into a narrow feed of Pacific moisture.
Farther south derived imagery is showing sub-tropical moisture
actually moving up the Baja California coast due to the cyclonic flow around
the western ridge...while farther west a branch of the sub-tropopause jet
is pushing mositure toward Southern California. Theta surfaces show
this source of moisture drifting overhead early Sunday morning as
our flow veers more westerly by the approaching trough. Precipitable water
increases up to near half of an inch but cross section show the bulk
of this moisture as high level cloudiness and outside of the
dendritic layer. There is some jet dynamics to add ascent to
orographics but still not confident much will come out of it besides
virga or light sprinkles so have backed off on some
probability of precipitation...especially in the valley locations. Cloud cover will still
impact the temperature forecast and highs will be knocked down
several degrees...but stay above normal.

The ascent associated with the passing trough Sunday night into
Monday appear to focus north...then east...then south of our County Warning Area
looking at the qg parameters. The favored area for the past models
runs remains across our northern mountains today and with this
confidence did boost probability of precipitation Sunday night over the park and Flat Tops
favored in westerly flow. Jet forcing and orographics will combine
with frontal forcing...cold air advection and instability across the far north and
we should the better conditions for snowfall...but for only about 6
to 8 hours. Will watch the trend but it appears 1 to 3 inches on the
peaks is still valid. The front continues to sag southward but
drying and weakening as it does so...showers will be scattered at
best in the eastern mountains. Drying and cooling behind the front
drops temperatures down near normal for Monday and will be a
rather significant change from the past week or so. Temperatures
Tuesday morning may bring some freezing temperatures to some areas
for the first time...but guidance not trending this way yet.
Ridging returns beyond this with another dry warmup expected to
end out next week.&&

Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1035 am MDT Friday Oct 24 2014

VFR conditions continue under clear skies through the next 24
hours.

&&

Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 457 PM MDT Friday Oct 24 2014

VFR conditions will continue for the next 24 hours under near
cloudless skies and light diurnal winds.

&&

Gjt watches/warnings/advisories...
Colorado...none.
Utah...none.
&&

$$

Short term...no layers
long term...15
aviation...cirrocumulus

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