Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 200242

Area Forecast Discussion
National Weather Service Denver/Boulder CO
842 PM MDT Sun Mar 19 2017

Issued at 842 PM MDT Sun Mar 19 2017

Winds have decreased this evening. The cross mountain flow will
increase again later tonight but not much evidence of a mountain
top stable layer upstream on the 00Z soundings. As a result,
gusty winds should stay up high for the most part. Temperatures
will remain very mild overnight with near record temps expected
again on Monday. Cold front will likely push into the northeast
corner of the state later tonight, but then wash out on Monday
before another surge arrives in the afternoon. Forecast on track
with only minor adjustments.


.SHORT TERM...(This evening through Monday)
Issued at 311 PM MDT Sun Mar 19 2017

A strong upper level ridge will continue to bring unseasonably
warm temperatures and dry conditions through Monday. Models
showing a mountain wave will form tonight. Not a great set up and
expect the strongest winds to be over the mountains and higher
foothills where gusts to 40 to 50 mph will be possible in the wind
prone areas. A weak cold front is expected to back into the
northeast corner of Colorado Monday afternoon. This should keep
highs a little cooler here. Elsewhere, airmass remains warm and
expect high temperatures close to today with readings in the upper
70s to lower 80s. Moisture aloft will pick up and increase cloud
cover Monday. A few showers will be possible late Monday afternoon
over western Colorado. These are expected to remain west of the
forecast area.

.LONG TERM...(Monday night through Sunday)
Issued at 311 PM MDT Sun Mar 19 2017

A flat upper ridge with moderately strong west-southwesterly flow
aloft will remain over the forecast area through Tuesday night.
QG omega fields indicate weak large scale ascent over north-
central Colorado with the passage of a couple of weak mid-level
perturbation. Anyhow, the first of these features is forecast to
pass over the fcst area Monday night, and the second one during
the Tuesday afternoon/evening time frame. Both features are
expected to produce scattered rain and snow showers in the high
country and possibly a few rain showers at lower elevations.
Although the chance for measurable rainfall on the plains looks
better late on Tuesday when models show a brisk and somewhat moist
southeast low-level flow spinning up into a Denver cyclone
southeast of the metro area. Models indicate lower 40s dewpoints
flowing up into this area during the afternoon producing sfc based
CAPES in the 300-480 j/kg range from southeast of Denver to
eastern Boulder/ southwest Weld counties. Shear profile produced
by the low-level cyclone and moderate swly flow at mid-levels
appears sufficient to spawn a couple brief, weakly structured
t-storms. The best chance for t-storms to form expected southeast
the Denver metro area where models qpf fields indicate a couple
tenths of an inch of precip during the evening hours. As the wave
moves east, should see a few rain showers forming over the
northeast plains overnight where we may see a few hundredths of an
inch of rain falling from them.

By Wednesday...upper ridge regains its hold on the region...
returning max temps at lower elevations to the upper 60s and lower
70s, and min RHS in the 20s. However through the day...a tightening
north-south pressure gradient is progged to increase south-southeast
winds on the plains, particularly east of the I-25 corridor in the
afternoon. Could see gusts exceeding 25 mph out there and with
low RHS, the rangeland fire danger will likely increase again.
Something to keep in mind going forward.

During the period Wednesday night through Friday...should see a
steady progression towards cooler and wetter conditions as a large
upper-level trough makes its way inland across the Great Basin
and desert southwest. The latest GFS, DGEX, ECMWF and Canadian
models now in better agreement as they all show the upper trough
moving over the 4-corners region on Thursday where it forms a
closed mid-level low. From there, the trough and upper low swing
east with a deep closed low anchoring over southeast Colorado
Thursday night. Although the DGEX is farther north with the 500 mb
low and the Canadian model placed it over n-cntrl New Mexico. By
Friday morning the GFS, EC and Canadian all show the low winding
up over the CO/KS/OK intersection and a rather strong northeast
flow wrapping moisture back into northeast Colorado. GFS is most
ambitious with the moisture particularly over the eastern fringe
of the forecast area. Since we`re looking at something five days
away, will just trend temps downward and trend pops upwards. But,
conceivably it could end up being cold enough for snow on the
plains with snow accums a possibility. Eastern fringe area could
also see locally heavy rainfall.

Finally, should see a return to warmer and drier conditions on
Saturday, and then back to cooler and wetter conditions on Sunday
with another shortwave trough passing over the region.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 842 PM MDT Sun Mar 19 2017

VFR conditions will persist through Monday. Winds at KDEN and KAPA
had switch to north/northeast, but will likely become variable
before transitioning to normal south/southwest winds by or shortly
after 06Z. KBJC should remain westerly overnight. For Monday,
westerly winds are expected to develop again by 18z with gusts
around 20 knots.


Issued at 842 PM MDT Sun Mar 19 2017

Only poor humidity recovery will occur tonight in and next to the
Front Range Foothills. This will keep fire danger elevated but for
the most part gusty winds should stay over the higher foothills
with lack of mountain top stable layer and wave enhancement.

On Monday, fire danger will be elevated with a continuation of
unseasonsably warm temperatures and very low humidities. Breezy
conditions can also be expected at times, but at this time winds
are forecast to be a little lighter than those observed today, and
just shy of Red Flag criteria. Highest fire danger in/near the
foothills and Palmer Divide. Will continue to monitor.




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