Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 181047
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
347 AM MST Sat Feb 18 2017

.SHORT TERM...(Today and tonight)
Issued at 347 AM MST Sat Feb 18 2017

Satellite shows the deep upper level trough off southern
California and Baja already becoming negatively tilted. This will
provide for short wave ridging and a return of warm advection
across Colorado today. There is some light snow falling over the
mountains toward the Rabbit Ears Pass area, but that`s about it.
Radar returns are already decreasing on the west slope so should
see a break in the light showers. By afternoon, enough heating and
moisture advection should bring a few more rain and snow showers
to the high country, but any accumulation would be light and
scattered with the very warm airmass and unfavorable southerly
flow for no orographic support.

On the plains, look for another mild day with return of warm
advection. Some clouds may hinder warming a couple degrees but
still some sunshine expected from time to time, favoring the
afternoon hours. Southerly winds will bring elevated fire danger
to the plains this afternoon, but humidities are not low enough to
warrant Red Flag conditions.

For tonight, any mountain showers will be ending in the evening
with stabilization and even more short wave ridging as trough
continues to become more negatively tilted along the
Arizona/Mexico border. This should also result in some clearing
skies, with cool but still above normal temperatures.

.LONG TERM...(Sunday through Friday)
Issued at 347 AM MST Sat Feb 18 2017

An upper level low will move quickly across the area Sun aftn
into Sun night. Both the ECMWF and GFS have this system nr Denver
by early Sun evening while the NAM is further south over sern CO.
For now will go with the further north solution. Meanwhile sfc
low pres will intensify nr the foothills with gusty sly winds over
the plains thru the aftn into the early evening hours. Aftn highs
will remain well abv normal with readings in the 60s across nern
CO.

As far as pcpn moisture will increase across the area along with
favorable mid lvl ascent by aftn thru the evening hours thus will
see an increasing chc of showers in the mtns by aftn with a slight
chc along the front range. As the main upper level tracks across
Sun evening should see a better chc of showers and possibly even a
few tstms across nern CO. In the mtns the mid lvl flow will
become more nwly Sun night which will lead to favorable
orographics and periods of snow. Late Sun night into Mon morning
as the upper level low moves northeast of the area there will be
some potential for high winds in and nr the nrn foothills as
component along winds increase to 50-55 kts.

On Mon drier air in nwly flow aloft will move into the area with
snow chances ending in the mtns during the morning hours.
Meanwhile with fairly stg flow in the mid lvls combined with
mixing expect gusty nwly winds to continue over the higher terrain
and across the plains. As for highs readings will remain mild with
temps in the upper 50s to mid lower 60s across the plains.

For Mon night into Tue the flow aloft will become more wly. There
will be some moisture affecting the mtns so will mention a slight chc
of -shsn. Across the plains it will be dry with well above normal
temps due to favorable downslope wly flow. Expect highs will reach
the upper 60s to mid 70s.

By Wed the flow aloft becomes more wsw with the GFS showing some
shallow moisture affecting the mtns while the ECMWF is completely
dry. Overall would probably favor the ECMWF solution so will keep
pops on the lower end at this point. Once again nern CO will be
dry with highs remaining well above normal.

On Thu an upper level trough will move into the rgn with the main
upper level low fcst to stay over WY. There are significant
differences between the ECMWF and GFS with handling of low lvl
features. The ECMWF has a sfc low over sern CO while the GFS has
the low further northeast over nwrn KS. As a result the ECWMF has
a fnt moving across nern CO with upslope component by aftn into
Thu evening while at the same time the GFS has a stg downslope
component instead. Furthermore the ECMWF has favorable mid lvl
ascent across the area while the GFS does not. Overall will see a
good chc of snow in the mtns with some potential for pcpn over
nern CO if ECMWF solution is correct. As for highs readings will
be colder as highs drop back into the 40s across most of the
plains.

By Fri the upper level trough will move east of the area with nwly
flow aloft. There will be some lingering moisture in the flow so
will keep in a slight chc of snow in the mtns. Across nern CO it
will be dry with blo normal temps for a chc as readings only reach
the upper 30s to mid 40s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 347 AM MST Sat Feb 18 2017

VFR conditions will persist, with only sct-bkn mid to high level
clouds above 10 thousand feet. Main issue today will be winds.
Denver cyclonic convergence zone should develop by this afternoon
so could see light/variable winds on the north side of zone, and
stronger southeast winds gusting to around 20-25 knots on the
south side of the zone. Right now, the boundary appears to set up
very close to KDEN 21Z-02Z which would have implications on
north-south operational plans. Will favor southeast winds during
this period in the TAF, and then adjust as needed per latest radar
and observational trends this afternoon/early evening.

&&

.FIRE WEATHER...
Issued at 347 AM MST Sat Feb 18 2017

Fire Danger will increase across the plains Mon afternoon due to
gusty winds and low humidity levels. The Fire Danger will also
remain high across the plains for Tuesday and Wednesday due to
well above normal temperatures, low humidity levels and gusty
winds at times especially in the afternoon.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Barjenbruch
LONG TERM...RPK
AVIATION...Barjenbruch
FIRE WEATHER...RPK



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