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Area forecast discussion 
National Weather Service Grand Junction Colorado
425 am MDT Monday Aug 31 2015

Short term...(today through tuesday)
issued at 425 am MDT Monday Aug 31 2015

A moist and unstable southwest flow will continue across the area
through Tuesday. This flow regime has been...and will continue to
be...the result of the area being positioned between general
troughiness along the West Coast and high pressure extending from
Texas into the Ohio Valley. A moderately weak upper jet stream will
stretch SW-NE across eastern Utah/western Colorado today...then will
become more west-east on Tuesday as the Texas high pressure center tries
to spread westward a little. Disturbances embedded in the
southwest flow...along with minor jet maxima...will stream over
the area at times today through Tuesday. Meanwhile...deep moisture
over Sonora to southern Arizona will continue to provide a source for
moisture to work northward towards the forecast area. However...
it does appear that the deepest moisture across western Colorado and
eastern Utah occurred yesterday afternoon through last night...but
the nam12 keeps close to an inch of precipitable water stretched
nearly to the Wyoming border through Tuesday.

For today...the lingering morning showers/thunderstorms will
increase during the afternoon as daytime heating combined with jet
support overhead boosts the convective potential. Isolated to
scattered late day activity will be possible across much of the
area...with better coverage over the mountains. Isolated storms
may produce small hail and heavy rain. However storms are not
expected to be as strong as what was seen Sun afternoon/evening.
Today lacks the significant shortwave and its associated cold
front that passed to our north sun evening. Also less nocturnal
storms are expected tonight...however I would not rule out a few
overnight showers.

Tuesday looks to be a repeat of today. The NAM actually shows a slight
uptick in showers and thunderstorms as an embedded waves passes
during the afternoon.

Daytime temperatures will be near normal...with lows on the warm
side due to better moisture across the area.

Long term...(tuesday night through sunday)
issued at 425 am MDT Monday Aug 31 2015

The synoptic pattern featuring a mean trough over the Pacific
northwest and a ridge of high pressure over the Central Plains
will persist during the medium range period. Moisture over the
region erodes as the subtropical moisture plume is forced just to
the east at midweek. With less fuel for moist convection...
diurnally driven storms will become more isolated in coverage
Wednesday into Thursday. As has been the case over the past
several weeks...the San Juan Mountains will be right on the edge
of the moisture plume and therefore...the favored location for

Activity is indicated to increase Friday and Saturday as the
Pacific northwest trough first digs southward Friday...then
ejects another shortwave trough across the northern rockies
Saturday. The European model (ecmwf) solution not quite in sync with the GFS
solution...but similar. However...minor variances in flow seemed
to have significant impact on moisture advection with the European model (ecmwf)
markedly drier Friday. Given model differences...left probability of precipitation in the
low scattered coverage category both Friday and Saturday. By
Sunday...both models were drier except over the San Juan

Forecast temperatures reflect the quasi-stagnant pattern described
at the beginning of this section and are projected to remain
within a few degrees of normal throughout the period.


Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 425 am MDT Monday Aug 31 2015

Scattered showers and a few lightning strikes will continue along
the I-70 corridor...northwest Colorado...and the eastern Uinta
Mountains this morning. This activity will generate little wind
and ils breakpoints are unlikely to be impacted except possibly at
kase. Expect shower and thunderstorm activity to increase over the
mountains after 18z...continuing through 02z/Tue. There is roughly
a 30 percent chance that storms will move over airports across the
forecast area and lesser chances for visibility or ceilings to be
significantly impacted. A few storms may linger past 02z but
chances for impacts on aviation are quite small.


Gjt watches/warnings/advisories...




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