Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 160259

Area Forecast Discussion
National Weather Service Denver/Boulder CO
859 PM MDT Thu Mar 15 2018

Issued at 851 PM MDT Thu Mar 15 2018

No significant changes at this time. Main center of the upper low
apparent on radar, over southeastern Weld County. As this feature
shifts to the east, then wrap around moisture will fill into the
northeast plains overnight. Best round of pcpn for the Denver area
appears to be this evening, then the focus will shift to the north
and east. Some minor adjustments in terms of timing this evening,
have delayed the higher pops by a couple of hours, otherwise will
leave the rest of the grids.


.SHORT TERM...(This evening through Friday)
Issued at 315 PM MDT Thu Mar 15 2018

Water vapor satellite imagery showing the upper level trough
tracking across the Great Basin at this time. At the surface, a
broad low is centered over east central Colorado. This surface low
is bringing northeast to east winds to most of northeast
Colorado. The easterly winds will also advect moisture into the
area. Snow showers will continue to increase over the mountains
this afternoon as the upper level trough nears the state. Showers
will progress eastward onto the near by plains late this
afternoon. Surface based CAPE climb to 200-400 J/kg late this
afternoon, so expect a few thunderstorms over the mountains and
the plains through early evening.

Going forecast of 5-10 inches of snowfall for the mountains
appear on track and will continue with the Winter Weather
Advisory. Snowfall rates under heavier showers and thunderstorms
will be near 2 inches per hour. However, this intense rate will be
short lived.

Biggest forecast challenge will be the potential for snow and
strong winds on the eastern plains. The last few runs of the RAP
and HRRR have been slower with moving the surface low out of
Colorado. The latest model trends have also been a little more
north than the previous runs. The position of the surface low will
help determine where a band of rain/snow forms. Precipitation
intensity and the surface low pulling in cold air should make it
cold enough for snow after midnight across parts of the plains.
Will go with a Winter Weather Advisory for the northeast plains.
Snowfall amounts will greatly very depending on where the band of
heavy precipitation forms. A few locations may see up to 6 inches.
Winds will also be a concern as the surface low deepens. Will go
with gusts to 50 mph and blowing snow in the advisory as well. If
the low intensifies and slows even more. Some areas may need a
High Wind Warning/Blizzard Warning, all depends where the band of
snow forms.

As far as the High Wind Watch goes for the foothills, will cancel
it. Models do show a mean state critical layer, however winds
speeds in the models along the east slopes stay well below high
wind criteria. Will go with gusts to 60 mph at this time as it
does look windy.

.LONG TERM...(Friday night through Thursday)
Issued at 315 PM MDT Thu Mar 15 2018

After Friday`s weather system moves off to the central plains, an
upper ridge will build over the state with drier and warmer
weather. Mild southwest flow aloft will be dry. The flow pattern
across the western half of the country will be progressive as a
developing trough over the west coast moves inland Saturday night
and Sunday morning. Much like today`s upper system moving over the
desert southwest, the next trough will track eastward through
Sunday night. The latest runs of the medium range models are in
fair agreement with positioning of the upper level low over
northeast New Mexico Sunday evening. At the surface, a low
pressure area is forecast to develop over southeast Colorado. This
should produce another round of precipitation across the mountains
and northeast plains. Quasi-geostrophic diagnostics shows another
period of decent rising motion across eastern Colorado.
Temperatures will again be critical as to whether precipitation on
the plains falls as rain or snow. We will be watching the next few
runs for where the best place to put the rain/snow line on the

Monday and Tuesday look like moist westerly flow producing a
little more snow in the mountains and dry conditions on the
plains. A passing shortwave Tuesday night or Wednesday morning
will produce some more showers across the forecast area. Beyond
that, a strong ridge over the western United States will bring
drying and warming back to the region.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 851 PM MDT Thu Mar 15 2018

Areas of MVFR conditions are expected through this evening due to
showers. Still some uncertainty in the placement of precipitation
bands which could lead to lower visibilities, especially at KDEN
late this evening. Wrap around moisture from the upper trough
could impact KDEN by 06z and continue until 09z. Do not expect
cigs and vsbys to be as bad at KBJC and KAPA after 06z.


Winter Weather Advisory from midnight tonight to noon MDT Friday
for COZ042-044-048>051.

Winter Weather Advisory until 9 AM MDT Friday for COZ031-033-034.



LONG TERM...Dankers
AVIATION...Cooper is the U.S. government's official web portal to all federal, state and local government web resources and services.