Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Denver/Boulder Colorado
405 am MDT Tuesday Sep 30 2014

Short term...(today through tonight )
issued at 400 am MDT Tuesday Sep 30 2014

Deep upper air cyclone centered over extreme northwestern Nebraska at
this hour will continue to quickly track north-northeastward across
North Dakota this morning and then up over Manitoba later today.
Strong middle-level subsidence on the back side of this departing low
pressure system was now over Colorado. NAM and rap qg vert velocity
fields and on water vapor Sat imagery nicely reveal this sinking.
Stabilization of the mountain top layer past few hours has produce a
standing mountain wave along the Front Range...resulting in gusty
west-northwest winds at higher elevations of the Front Range. NAM
and rap cross sections indicate cross barrier winds in the
45-55kt range by around 12z this morning...then only slightly
weaker at 15z. Wind sensors atop the high ridges were already
indicating gusts in the 45-55 miles per hour range. Could see some of this
momentum spreading to lower east slopes of the Front Range during
the next few hours. Do not see winds reaching high wind criteria
at this time. Furthermore...do not anticipate these strong winds
will spread out onto the nearby the plains. Although the
northeast corner of the County Warning Area could see west-northwesterly wind gusts to 40 miles per hour
late this morning and early this evening with momentum mixing down
from aloft.

Clearing early this morning will give way to increasing middle and
high clouds east of the mountains later today. Cloudy skies will also
return to areas along and west of the Continental Divide with a
weather disturbance racing in from the northwest. Qg vertical velocity reverse
and go positive this afternoon as this next wave of moisture and
energy nears. Could see scattered showers and isolated T-storms
in the mountains and high valleys by middle- to late afternoon. Snow level
will Hoover around 11 thsnd feet today...and drop to around 9500 feet
this evening. However any snow accumulation should be minimal.
By evening skies should also fill with clouds east of the mountains as
this weak pertabation passes by...then partial clearing late
with its departure. Precipitation is not anticipated through 12z/Wednesday east of
the mountains

Long term...(wednesday through monday)
issued at 400 am MDT Tuesday Sep 30 2014

The next upper level trough will move across Colorado on Wednesday
afternoon and night. An associated cold front will move across
northeast Colorado during the afternoon hours with increasing
northerly flow at low levels. Qg fields showing increasing ascent
during the day Wednesday...peaking over the Front Range in the
afternoon and further east on the plains during the early evening.
Short range models are fairly consistent on timing with this trough. Given
the front and forcing aloft will bump probability of precipitation up further to likely
over most sections during Wednesday afternoon and evening. The
trough is quite progressive so showers will end from northwest to
southeast Wednesday night as precipitation duration will be in the 3-6
hour range. The airmass will be cold enough to support some snow
accumulation in the mountains.

For Thursday and beyond...there will be a drying and warming trend
as Colorado will be under a moderate...northwest flow pattern.

&&

Aviation...(for the tafs through 12z Wednesday morning)
issued at 400 am MDT Tuesday Sep 30 2014

VFR conditions will prevail at Denver area terminal and gates
through 12z/Wed. Although ceilings may lower below 10 thsnd feet
above ground level after 22z today and possibly lower to around 8 thsnd feet above ground level
early this evening as a weak upper air disturbance passes by. At
this time...do not anticipate any precipitation with this system. Expect
drainage winds of 5-12kts at dia and apa through middle-
morning...then a gradual clockwise shift to westerly winds of 7-14kts
by midday where they should remain through early this evening
before resuming a typical drainage pattern. On the other hand
..west-southwest winds of 10-25kt can be expected at bjc near the
foothills through midday...then 7-13 northwesterly winds in the
afternoon...and then S-southwesterly winds of 4-8kts overnight.

&&

Bou watches/warnings/advisories...
none.
&&

$$

Short term...Baker
long term...entrekin
aviation...Baker

National Weather Service Glossary of Abbreviations