Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 152130

Area Forecast Discussion
National Weather Service Denver/Boulder CO
330 PM MDT Mon May 15 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 330 PM MDT Mon May 15 2017

Satellite and radar pictures are showing a little bit of
convection in the high mountains. There is a pretty decent
boundary over the plains moving north-northwestward with pretty
dry air behind it. There is a little bit of Cumulus development on
that boundary. Models have southwesterly flow aloft to continue
over the CWA overnight. Is it progged on Tuesday, but speeds
decrease by afternoon. The QG Omega fields show weak upward motion
tonight, and a bit stronger on Tuesday. Boundary layer winds are
mix of normal diurnal patterns and downsloping overnight. Speeds
are not significant. There is some easterly flow over the plains
Tuesday, then a front of sorts moves in by the end of the day. The
front is better detected on the thickness fields. For moisture it
is pretty dry overnight into Tuesday morning, then there is an
increase from the west. Dew point temperatures are mainly in the
40s for the plains Tuesday afternoon. Lapse rates are pretty steep
for most areas Tuesday afternoon. There is okay CAPE over much of
the CWA Tuesday afternoon, with some areas have around 1000 J/kg.
I will go with minimal pops over the high mountains this evening.
On Tuesday, WIll increase pops from west to east after 18Z. Will
go with 20-50%s by late evening adjoining the even period. For
temperatures, Tuesday highs look to be some 3-6 C cooler than this
afternoon`s highs.

.LONG TERM...(Tuesday night through Monday)
Issued at 330 PM MDT Mon May 15 2017

A pair of weather systems moving over Colorado through the latter
half of the week will bring several days of cool and unsettled
weather to the forecast area. Each of the models show an initial
short wave trough moving over the state tomorrow night which will
help keep afternoon shower activity going through the evening
hours. Shower activity and a surface cold front moving into the
region will cool temperatures off through Wednesday as a weak
upper level ridge develops. The ridging will be short lived as a
stronger upper low quickly drops into place over the Great Basin
by Wednesday evening. The medium range models all move this upper
low slowly over Colorado through Friday morning. Quasi-geostrophic
diagnostics shows a decent amount of synoptic lift with this
system through the day Thursday. Cold air associated with the
system will move over the mountains and drop snow levels down to
6500 or 7000 feet. Areas on the plains may even see some snow
mixed in with the rain at times Thursday and Friday mornings.
Model QPF fields are generating healthy amount of precipitation,
possibly more than an inch across the plains. In the mountains,
snow accumulations may approach a foot above 10,000 feet. Will not
issue any highlights at this point due to uncertainty in the track
and eventual strength of this late season storm system.

The exact track of the system is still in question with each of
the models restricting the coldest air to the mountains and
northwest quarter of the state. If the upper low dives further
south than presently forecast, then even cooler temperatures may
develop across northeast Colorado. For the time being will have
lows on the plains down to the 32-37 degree range, but remaining
above freezing. Thursday and Friday morning both promise to be
quite cool. The upper low will still be lingering over northeast
Colorado Friday afternoon, meaning showers could still be ongoing.
Improving conditions are expected over the weekend as the upper
system finally moves on to the northern plains.

Saturday and Sunday will see gradual moderation in temperatures as
shower activity tapers off. Early next week looks like
northwesterly flow across Colorado as a ridge builds over the
northeast Pacific. Showers may increase again Monday afternoon.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 330 PM MDT Mon May 15 2017

East-southeasterly winds are continuing over DIA at this time.
There is a decent boundary with southerly winds behind it moving
slowly northward right now. This should get into DIA between 22Z
and 23Z. Close to near normal drainage patterns should persist
tonight. There will be no ceiling issues until later Tuesday


Red Flag Warning until 7 PM MDT this evening for COZ214.



LONG TERM...Dankers
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