Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 221046
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
446 AM MDT Wed Mar 22 2017

.SHORT TERM...(Today and tonight)
Issued at 446 AM MDT Wed Mar 22 2017

Cooler air with southeast winds across the plains today. There
are some low clouds along the eastern border, but the air is drier
further west. Expect these clouds to dissipate during the day, but
it will help keep temperatures cooler near the border.

Meanwhile the mountains are in a warmer and drier southwest flow
ahead of the approaching system. There may be some minimal
convection this afternoon, but the main story will be increasing
wind, especially overnight. South to southwest direction is not
favorable for our normally windy areas but will hit some spots
that don`t usually blow too hard, especially southwest of Denver.

The Denver area will be in between these two regimes. The
combination of the plains winds and inversion will maintain a
Denver cyclone with some kind of lighter northerly wind prevailing
across the city much of the day. HRRR insists on gradually washing
out the cyclone and bringing some warm/dry west winds off the
foothills late in the day. This looks overdone. Upgraded NAM is
actually capturing the circulation fairly well, so its wind fields
were used heavily this morning.

Some moisture increase overnight may bring light showers to the
mountains, but this should be limited and the snow level will
remain high, between 9 and 10 thousand feet.

.LONG TERM...(Thursday through Tuesday)
Issued at 446 AM MDT Wed Mar 22 2017

On Thursday, one more warm day ahead of our incoming storm system.
Gusty southerly winds, coupled with low relative humidities and
dry fuels will elevate the fire danger along the Palmer Divide
region in the afternoon, reference the discussion below. Next
trough over the Great Basin region 12z Thursday, will be near the
Four Corners region by 00z Fri, and intensifies over sern CO by
12z Friday. All the mdls are in fairly good agreement regarding
its location by 12z Friday. Mid level qg ascent increases rapidly
over east central CO Thu aftn, Weak to moderate qg ascent over
northeast CO Thursday aftn, with enough instability to warrant a
slgt chc of tstms. Rain and snow showers will develop in the
mountains during the day, but the intensity of the pcpn will pick
up significantly Thursday evening, with strong qg ascent over
eastern CO as the upper low closes up over sern CO. Increasing
northeasterly upslope with the ams saturating THU night. Should
see heavy snowfall develop in the Front Range Mountains and
foothills especially from Jefferson County southward overnight.
Heaviest snowfall will be 03z to 15z Friday, then the low and mid
level flow transition to northerly through the day Friday. Snow
level still a big question mark for the Urban Corridor, but the
mdls have been trending a little colder, nudging the snow level a
little lower. No highlight yet since its the fourth period, but
will likely need to hoist a Winter Storm Watch later today for the
Front Range Mountains, Foothills and possibly the Monument Ridge
above 6 kft or ZN 41. Very strong northerly winds gusting to 50
mph on Friday will likely produce blowing and drifting snow over
the Palmer Divide as well. Mdls still showing rain or a mix of
rain/snow for most of the the urban corridor but could see some
accumulating snowfall above 5500 feet near the foothills of
Jefferson/Douglas Counties. Gradient from rain to snow will likely
be pretty tight. Further north, if the low and mid level flow
transitions to northerly too fast, than downslope off the Cheyenne
Ridge could be stg enough to keep mainly rainfall north of
Boulder. Storm will transition to the plains of CO on Friday as
the system makes its way into scentral KS/northern OK by 00Z
Saturday, with diminishing pcpn fm west to east Friday night.
Trend for drier and warmer on Saturday still on track. The next
system is progged to move across CO midday Sunday so another chc
of snow mountains with rain across northeast plains Sunday
aftn/evng. Drier Sunday night into Monday, with another chc of
pcpn for the region by Wednesday of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 446 AM MDT Wed Mar 22 2017

VFR through tonight. Winds will remain a challenge for KDEN and
KAPA as a Denver cyclone circulation will wobble around resulting
in wind shifts. By 19z we expect the south winds on the plains
will shift east of the airports, with light northerly winds this
afternoon. Sometime tonight the winds will likely become southerly
again.

&&

.FIRE WEATHER...
Issued at 446 AM MDT Wed Mar 22 2017

Low humidities and mixing of southwest winds to the surface may
result in conditions approaching Red Flag criteria for a few hours
this afternoon in South Park and the foothills from Boulder county
southward. There is a small chance these conditions could spread
down across the lower foothills and into the Denver area, Douglas
and western Elbert counties. Elsewhere humidities will be higher.

On Thursday, combination of gusty southerly winds ahead of the
next storm system coupled with dry fuels and very low relative
humidities under 15 percent warrant a Fire Watch in the aftn. Main
concern will be east of I25 and south of I76 where it is progged
to be the windiest and the driest. Cooler temperatures and decent
pcpn across the cwa should put an end to the fire weather concerns
through the remainder of the forecast period.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch Thursday afternoon for COZ240-241-245>247-249.

&&

$$

SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Gimmestad
FIRE WEATHER...Cooper



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