Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 121630

Area Forecast Discussion
National Weather Service Denver/Boulder CO
930 AM MST Sun Nov 12 2017

Issued at 930 AM MST Sun Nov 12 2017

Windspeeds across the plains are increasing slightly faster than
forecast. Have increased speeds and adjusted timing. Otherwise no
adjustments needed.


.SHORT TERM...(Today and tonight)
Issued at 206 AM MST Sun Nov 12 2017

High pressure at the surface and aloft will be over the region
today. The flow aloft will be westerly and a little weaker with
the ridge overhead. Across the northeast plains, surface high
pressure will be in place this morning then will gradually shift
eastward this afternoon. Temperatures today will be 3-5 degrees
cooler than Saturday. For tonight, NAM12 spatial cross-sections
indicate the development of a mountain wave after 03z. Cross
mountain component of 40 kts at 700 mb which could translate to
gusts around 50 mph in the east mountain slopes and higher
foothills. A lee side trough is expected to develop along the
Front Range, which should help to strengthen the sfc pressure
gradient west of the trough. Temperatures will not be as cold in
the windier area where downslope will be the strongest. Some
mountain wave cloudiness can be expected across the northeast
plains, with mostly cloudy conditions developing overnight.

.LONG TERM...(Monday through Saturday)
Issued at 206 AM MST Sun Nov 12 2017

A fast westerly flow aloft over the western U.S. is still on
track for the upcoming week. Ridging in the westerly flow will
move across Colorado Monday. Temperatures will climb well above
normal with 60s and perhaps a few lower 70s across northeast
Colorado. Windy conditions will be possible in the mountains and
foothills Monday morning.

It will remain mild Tuesday as an upper level trough tracks
across Wyoming and Montana. Models are a little drier, and keep
precipitation north of Colorado with this system. However, windy
conditions will be possible near the Wyoming border. A cold front
will push south through eastern Colorado late Tuesday. This will
result in cooler temperatures Wednesday even though weak ridging
will be moving across Colorado.

The next wave embedded in the westerly flow aloft is expected to
push across the region in the Thursday/Friday time range. There is
still differences on the timing and strength of this system. The
GFS is quicker than the ECMWF. Mountains should see a period of
snow with this system. Wouldn`t be surprised to see a few showers
along the Front Range and over the eastern plains with a 160 knot
jet over the area. Will have low pops in the forecast for
northeast Colorado Thursday night and Friday. If precipitation
occurs east of the mountains, it will be light and short lived.
Temperatures will be warmer on Thursday ahead of this system.

Models continue to diverge for next weekend with a ridge on the GFS
model and a cooler northwest flow aloft on the ECMWF. Both models
are dry. Will go with temperatures near normal with readings in
the 50s across northeast Colorado.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 930 AM MST Sun Nov 12 2017

VFR today and tonight. Southeast winds this morning will be
increasing in speed. A Denver Cyclone will set up - high res
models are having a difficult time determining where it will move.
Currently near APA, on average it should move to the northeast
toward DEN. Therefore the wind forecast is difficult for DEN and
confidence is low at this point. For now, believe the stronger SE
winds will continue for the next 2-3 hours then decrease as the
Cyclone nears....and may even turn NW if the cyclone pushes east
of the airport. Have adjusted the winds at least weaker after 22z,
but may have to eventually turn them NW. Otherwise expect the
winds to then turn south/southwesterly later this aftn and
tonight at KDEN and KAPA. At KBJC, east/southeast winds expected,
with a west component possible after 06z tonight. Generally, the
wind should be at or below 10 kts.




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