Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus65 kbou 180955 
afdbou

Area forecast discussion
National Weather Service Denver/Boulder Colorado
355 am MDT Wed Sep 18 2019

Short term...(today and tonight)
issued at 353 am MDT Wed Sep 18 2019

Satellite pictures are showing a few clouds over the far western
County Warning Area at this time, otherwise it is clear elsewhere. Models have 30
to 60 knot southwesterly flow aloft at the jet level over the County Warning Area
today and tonight. A fairly significant upper trough is progged to
move into the northern Great Basin by 12z Thursday morning. There
is no synoptic scale energy for the County Warning Area on the qg Omega fields
today or tonight. The low level pressure and wind fields show
southeasterly winds for much of the forecast area today, and
normal drainage patterns overnight. A Denver cyclone is likely to
develop this afternoon. For moisture, precipitable water values
are progged in the 0.50 to 0/75 inch range from west to east
today and this evening. There is slight drying aloft over the
western County Warning Area later tonight. The low level moisture is lacking much
of today, however later in the day and tonight, it increases
somewhat from west to east. There is some minor cape over the
mountains and foothills this afternoon. The lapse rates on cross
sections show a weak mid level cap over the County Warning Area this afternoon.
The quantitative precipitation forecast fields show a small amount of measurable rainfall over the
mountains, foothills and adjacent plains this afternoon and early
evening. Will leave a some 10-20% pops in over the mountains and
foothills this afternoon. Dry for the plains. For temperatures,
today's highs look to be 3-5 c cooler than tuesday's highs.

Long term...(thursday through tuesday)
issued at 143 am MDT Wed Sep 18 2019

With a fairly amplified ridge/trough pattern over much of the US
Thursday, Colorado remains under moderate to strong southwest flow
aloft. As a cool Pacific trough moves into the northern Great
Basin Thursday morning, a massive ridge will cover much of the
United States east of the Continental Divide. With sufficient
subtropical moisture under the southern portion of the ridge along
with weak mid-level qg ascent over much of The Rockies, scattered
showers and thunderstorms will be expected over the higher
mountains for Thursday. With the forecast soundings indicating
drier conditions in the lower levels along with southwesterly
downslope flow, only gusty isolated shower and storm coverage is
expected for the foothills and plains.

The best qg ascent arrives over the region late Thursday into
Friday morning and with a tightening of the height gradient by
midday Friday, the main trough axis will pass across northeast
Colorado with strong subsidence to follow Friday evening into
Saturday. For Friday afternoon, with strong and drier
southwesterly flow in the mid and lower levels, will need to
watch for the potential for critical fire weather conditions over
central mountains, South Park and west Palmer Ridge region.

As the trough kicks northeastward into the Dakotas, a surface
front pulls southward with the exit of the main trough late
Friday into early Saturday. This will have cool enough air behind
it to bring highs for Saturday close to near seasonal averages.
Another weak and fast moving short wave rides into the central
rockies late Saturday night. This will push another dry surge into
the plains. Return flow from saturday's front will build a
Theta-E ridge along the Colorado/Kansas border and will likely be a focus
area for scattered thunderstorms across the eastern plains
Saturday night.

Weak ridging will develop over the central rockies during the day
Sunday and persist over the region through Monday. This will keep
the area dry as southwest flow aloft redevelops ahead of the next
trough expected Tuesday. Medium range models currently take this
deep and cold through into Southern California. This will be
watched over the next few runs to see if pulls up short and moves
into the central rockies. If so, it may have enough cold air
associated with it for the potential to mention snow over the
high country Tuesday.

&&

Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 355 am MDT Wed Sep 18 2019

Southeasterly winds are in place at dia behind a weak cold front
that moved across the area earlier this morning. Models show
south-southeasterly winds at the Airport this morning through
tonight. There will be no ceiling issues through the first two
periods and precipitation is not expected at dia.

&&

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

National Weather Service Glossary of Abbreviations