Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 111646
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
946 AM MST Mon Dec 11 2017

.UPDATE...
Issued at 927 AM MST Mon Dec 11 2017

Dry front making its way south into Colorado increasing winds from
the mid levels with gusts to 30 mph. RH levels still in the lower
to mid 20s but do expect them to drop slightly by the afternoon
into the teens and lower 20s. Continued high fire danger on the
plains given dry fuels and increased wind.

&&

.SHORT TERM...(Today and tonight)
Issued at 355 AM MST Mon Dec 11 2017

A relatively thick cloud band showing up on IR satellite imagery
extends from sern Montana to nwrn Nebraska along a nw-to-se
aligned baroclinic zone and nose of a 120kt jet. Models show these
features racing southeastward over swrn NE/nern CO/nwrn KS by
early to mid-morning, and the core of strongest winds aloft
passing just east of our forecast area around mid-afternoon.
Difficult to pin down the baroclinic/frontal zone attm. However,
model 850-700mb wind, moisture, temp and pressure fields show
this zone backing into nern Colorado mid to late morning, with the
best low-level cooling and strongest post-frontal nly winds during
the afternoon hours. Strongest winds are forecast to be east of a
Cheyenne-to-Limon line with peak gusts approaching 35kts for a
few hours this afternoon. With the cooler air, comes higher Rhs.
A Red Flag Warning has been issued for much of northeast Colorado.
warning runs from 11 am to 5 pm today. Wind speeds should certainly
meet the criteria for a warning, whereas min RH values may only
be marginal at best, esply in the cooler air across the nern
corner of the CWA. For now, will hold onto the warning with winds
as strong as they should be.

Elsewhere, such as along the Front Range, winds are not likely
to be anywhere as strong. HiRes models show some of the cooler air
on the plains backing into the I-25 corridor on light easterly
winds this afternoon. The incoming air does not appear all that
moist, and therefore if any any clouds are expected to form over
and along the Front Range. The high country will probably see
little more than a few deg drop in max temperatures from yesterday.

Tonight, the high plains cool air mass will continue to slip south-
southeast away from the area with light drier/warmer west-
southwesterly breezes by sunrise. In the high country, should see
another night of near zero readings and patchy dense fog on the
high valley floors such as around Kremmling.

.LONG TERM...(Tuesday through Sunday)
Issued at 355 AM MST Mon Dec 11 2017

Upper ridge of high pressure continues to meander around the
Western U.S. through Thursday with generally dry and mild
conditions for Colorado. There is a weak wave that moves over the
top of the ridge and across Colorado in the late Wed and Thursday
time frame. Looks like just enough moisture and weak QG ascent for
a chance of snow showers in the mountains but only minimal accumulations.
Some cooling of 10-15 degrees by Thursday behind the trof but
temperatures will still be above normal readings for this time of
year. For now will keep the plains dry, but models are hinting at
a few snow showers possible over the Palmer Divide.

There is some break down of the ridge by Friday and for the
weekend as a stronger northwest flow regime develops more moisture
in the flow. This should result in a bit more snow shower activity
and gusty winds for the mountains from late Friday night through
the weekend. Still dry and mild over lower elevations with
downslope flow in place.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 927 AM MST Mon Dec 11 2017

VFR conditions will prevail through the period. Winds will
gradually veer around to the north with the passage of a dry cold
front to the east of KDEN. Expect NNW winds by 17z with NE
possible between 18 and 19z. Speeds will remain between 6 and 10
kts. Winds will move around to SE by the late afternoon before
going to drainage this evening.

&&

.FIRE WEATHER...
Issued at 355 AM MST Mon Dec 11 2017

Northerly winds will increase across the northeast plains of
Colorado later this morning behind a weak cold front. Could see
gusts in the 30-40 mph for a few hours this afternoon up along
the Wyoming and Nebraska borders and across Washington County
where the pressure gradient and winds aloft will be strongest.
Min RH values are expected to be slightly higher today with the
cooler temperatures especially under the intermittent cloud
coverage in Sedgwick and Phillips Counties. That said, the
stronger winds will be sufficient to produce critical rangeland
fire behavior. Therefore, the Red Flag Warning will still go into
effect at 11 AM MST today.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 5 PM MST this afternoon for COZ238-242-
244-246>251.

&&

$$

UPDATE...Bowen
SHORT TERM...Baker
LONG TERM...Entrekin
AVIATION...Bowen
FIRE WEATHER...Baker



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