Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 190222

Area Forecast Discussion
National Weather Service Denver/Boulder CO
822 PM MDT Sun Mar 18 2018

UPDATE Issued at 708 PM MDT Sun Mar 18 2018

Issued a Winter Weather Advisory for the Denver area, southern
foothills, eastern Adams, and eastern Arapahoe, and Washington
counties. With the earlier change over to snow expect snowfall
amounts of 2-5 inches in the Denver area. Roads are being slushy
in places, mainly at slightly higher elevations. As temperatures
falls and with the loss of sunshine, most roads should become
slushy or snow covered and be slippery this evening.

UPDATE Issued at 620 PM MDT Sun Mar 18 2018

Strong spring storm will race across the region tonight.
Precipitation west of I-25 has changed to snow or will shortly in
the few locations it hasn`t. Nudged snowfall amounts up a little to
reflect the earlier change over the snow. This puts snowfall amounts
in the 2-4 inch range for the Denver area. HRRR and RAP models show
the precipitation ending in the metro area around or a little before
midnight. If the heavy precipitation rates linger for a few hours or
if it appears snow will last a little longer may need to expand the
winter weather advisories.


.SHORT TERM...(This evening through Monday)
Issued at 258 PM MDT Sun Mar 18 2018

Satellite pictures are showing an oblong circulation right over
the four corners at the bottom of the upper trough to our west.
Convection is breaking out over the high mountains and foothills
and Palmer Ridge at this time. There is a bit of lightning
detected over southwestern Larimer County. The cloud shield of the
system is slow to get across the CWA. Have been backing
off/delaying the cloudiness on the GFE grids all day. The wind
field over the plains shows mainly northeasterlies in place at
this time. The 12Z models all show an upper closed low over the
northeastern corner of the Texas Panhandle at 06Z and over
southeastern Kansas at 12Z. I suppose it better get moving.
Weakening zonal flow aloft is progged all day Monday. The
strongest QG ascent is progged at 00Z late this afternoon. The
system is moving quickly and by 06Z-09Z tonight downward energy
is in place over the CWA; pretty strong too. The low level winds
are progged to be north-northeasterly into mid evening, then more
north-northwesterly for the rest of tonight. They are due
northerly all day Monday. Moisture-wise, there should be plenty
over the CWA tonight, and fairly deep as well. Models have quite
a bit still around on Monday too. The QPF fields have measurable
precipitation across all of the the CWA tonight. There is some in
the high mountains all day Monday. Overall, the 12Z model runs
showed a bit less precipitation than the previous runs. Will keep
the current highlights going as is. Strong wind gusts will cause
havoc to travelers later tonight with blowing snow. Areas under
decent convection could see more precipitation and snow then is
expected otherwise. Monday`s highs will be about 10-15 F below
normals for the plains and foothills.

.LONG TERM...(Monday night through Sunday)
Issued at 238 PM MDT Sun Mar 18 2018

By Monday night, the upper level trough will push eastward bringing
NW flow over the state. Conditions on the plains will be dry, but
some light snow will continue in the mountains with model cross
sections showing decent mid level moisture through the morning
hours. Less than an inch in accumulations will be possible.

Tuesday and Wednesday will see upper level ridging increasing
bringing a period of dry conditions and warming temperatures.
Temperatures should rebound back to above normal conditions with
highs in the 60s.

The next weather system will be moving onshore over the western
coast by Thursday with continued ridging over the state. WAA will
increase 700mb temps in the +6-7C range. This will give surface
temperatures on the plains of lower 70s, the warmest day of the
week. In the mountains, increased subtropical moisture from the SW
ahead of the trough will bring increased chances of light rain and
snow to the western slopes through the day Thursday. Thursday night
into Friday and upper level shortwave combined with some CAA from
the WNW will help to bring cooler temperatures and accumulating snow
to the mountains Thursday night into Friday. A deep surface low over
the CO/KS border will help to maintain dry conditions on the plains
through Friday morning according to the GFS. The EC is slightly
slower with the progression of the upper level energy that could
bring a slight chance of rain to the plains by Friday afternoon.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 815 PM MDT Sun Mar 18 2018

IFR and LIFR cigs and vsbys due to snow and fog exist at all
Denver area air terminals as of 02z/Monday. These conditions are
expected to improve first across northwest portions of the metro
area such as at KBJC within the next few hours, then at KDEN by
around 07z/tonight, followed by KAPA an hour or two after that.
Roads and runways could become snow and/or slush covered with
slowly falling temperatures, if they haven`t done so yet. However,
road surfaces remain rather warm, so serious ice accumulation is
not anticipated. Should see MVFR conditions at all airports by 10z
tonight and VFR conditions on or before 12z/Monday with this
latest storm system racing off to the east. Winds are forecast to
remain northerly overnight at sustained speeds of 10-22kts, with
higher gusts in the 20-30kt range prior to 07z tonight.


Winter Weather Advisory until 6 AM MDT Monday for COZ035-036-

Winter Weather Advisory until noon MDT Monday for COZ031-033-034.



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