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Area forecast discussion
National Weather Service Denver/Boulder Colorado
812 PM MDT Tue Jul 23 2019

Update...
issued at 805 PM MDT Tue Jul 23 2019

Scattered showers and thunderstorms are showing a weakening trend
and now mainly confined across southern Summit and park counties.
Still some lightning, light to moderate rainfall and gusty winds
with the lingering showers. Expect all this activity will diminish
by around 10 PM with clearing skies overnight. Will adjust
evening forecast with latest trends. Should see more activity move
over the plains Wednesday afternoon as the upper high shifts a
bit more southward.

&&

Short term...(this evening through wednesday)
issued at 246 PM MDT Tue Jul 23 2019

There are only a few showers over the mountains and foothills at
this time. There is very little convective cloudiness over the
plains at this time. Models have the upper ridge center over The
Four Corners tonight and Wednesday. The flow aloft will remain
northwesterly tonight and Wednesday. There is benign synoptic
scale energy over the County Warning Area tonight and Wednesday. Models are now
showing just limited amounts of of measurable rainfall this
evening mainly over the mountains and foothills. Rainfall coverage
and amounts are considerably higher on the models for Wednesday
afternoon. Will pear down the pops this evening over the mountains
and foothills and will go with almost nothing for the plains.
Pops look to be higher late day Wednesday. For temperatures,
wednesday's look to to be 2-3 c warmer than this afternoon's
highs.

Long term...(wednesday night through tuesday)
issued at 246 PM MDT Tue Jul 23 2019

With the upper ridge continuing to dominate the region into
Wednesday, a fast moving Pacific trough treks across southern
Canada while pushing slightly cooler surface air southward onto
the High Plains. By late Wednesday evening this cool surge reaches
northern Colorado. Cape values for Wednesday afternoon and evening
reside in the 800-1800 j/kg range and with the weak late day surge
this may keep some storms going later into the evening hours
especially near the Cheyenne Ridge and far NE I-76 corridor. With
specific humidities holding above 8 g/kg, any storms that hold
together will likely contain heavy rain. With the flattening of
the ridge and zonal flow over the northern states this should
allow for much quicker storm motion as flow aloft becomes more
westerly.

With little change to the stagnant upper ridge pattern Thursday, a
similar moisture, instability and sounding profile holds across
the region. With light easterly low level winds expected across
the plains during the day, moisture content in the lower to mid-
levels will remain fairly high. Another round of scattered
afternoon and evening storms containing potentially containing
brief heavy rain will be expected.

Much drier air builds into northern Colorado for Friday as the upper ridge
reamplifies behind the first passing Canadian disturbance. Enough
subtropical moisture under the ridge will still be in place for
scattered afternoon and early evening showers and storms. Forecast
soundings for Friday afternoon would indicate storms
characteristics mostly containing gusty outflow winds.

By Saturday, a second fast moving trough skirts the US/Canadian
border. This flattens the ridge once again while sending an even
cooler surface surge southward into the area. A better coverage of
late afternoon and evening thunderstorms coverage will be
expected, again most numerous near the higher terrain with less
coverage out on the plains. This cooler surge of air will bring
the coolest temps in the extended forecast for Sunday with highs
likely retreating back into the upper 80s. After this second and
last Canadian trough which passes over the northern states, the
ridge ridge restrengthens for late Sunday into Tuesday. Enough
stagnant subtropical moisture will be available under the ridge
for scattered afternoon and evening storms near the higher terrain
with temperatures rising back into lower to mid 90s.

&&

Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 805 PM MDT Tue Jul 23 2019

Expect winds to settle down to more south and southeast at 03z at
kden after a an hour of erratic winds as circulation center moved
right over the airfield. Otherwise typical drainage winds tonight
and then a better shot for thunderstorms on Wednesday afternoon.

&&

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

$$

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