Johnstown, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

161
FXUS65 KBOU 150511
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1011 PM MST Thu Nov 14 2024

.KEY MESSAGES...

- Dry through Friday with above normal temperatures.

- Chance for light snow on Saturday in the northern Mountains.

- Another storm system is expected to arrive by Tuesday with
  colder temperatures along with a chance of snow across the
  region.

&&

.UPDATE...
Issued at 825 PM MST Thu Nov 14 2024

Current satellite pictures show no cloudiness over the CWA at this
time. There is some upper level cloudiness west of the CWA pushing
northeastward in the southwesterly flow aloft. In the lower
levels, weak drainage winds are in place across all the CWA.
Temperatures are mainly in the 30s across the plains, with some
teens and 20s in the alpine valleys and mountains. Again this
evening, there is very little to change in the grids; just some
minor tweaks to sky cover, temperatures and winds.

&&

.SHORT TERM /Through Friday/...
Issued at 115 PM MST Thu Nov 14 2024

Upper level ridging over the region is bringing sunny skies to
the state today. Most areas across northeast Colorado have climbed
into the upper 50s to mid 60s. However, it`s still quite cool
over the snow covered areas across the plains with temperatures
hovering around 40 degrees. For tonight, clear to mostly clear
skies will continue with mainly light winds. This will result in
prime radiational cooling conditions again. The mountain valleys
will be the coldest with lows in the single digits and teens. The
cooler low lying areas under the inversion across the plains are
expected to fall into the 20s with teens possible where there is
snow on the ground. Over/near the base of the foothills, above the
inversion, low temperatures will be mild with readings in the 30s
to lower 40s.

For Friday, southwest flow aloft will increase through the day
ahead of an upper level trough over the Great Basin. This will
bring windy conditions (gusts to 40 mph) to the higher terrain.
Southerly winds will also be breezy (~25mph) along the Palmer
Divide. This is expected to produce a Denver Cyclone Friday
afternoon. Northerly winds form on the backside of the cyclone
across western and northern parts of the Front Range, resulting in
slightly cooler temperatures. Highs will mainly be in the 50s
across northeast Colorado (except cooler over the snowpack).

&&

.LONG TERM /Friday night through Thursday/...
Issued at 115 PM MST Thu Nov 14 2024

Overnight Friday, an upper level trough will push eastward across
the western United States, resulting in dry southwest flow aloft
over Colorado. This pattern should lead to dry conditions and near
to slightly above normal temperatures.

As the upper level trough moves eastward on Saturday and Sunday, it
splits. One trough will travel over northern potions of the United
States, while a stronger closed low deepens over the Baja California
region. With Colorado being in-between these two systems, the best
chance for snow showers will be late Saturday afternoon over the
northern mountains. Due to limited moisture and weak
orographics, only light snow is expected in the high country. This
does match the NBM output which shows QPF less than 0.10" and
snowfall amounts less than an inch. Otherwise, models show dry
conditions and seasonal temperatures for the rest of the CWA
Saturday and Sunday.

For Monday, models are in more agreement that the upper level closed
low will have moved from Baja California into the Texas Panhandle by
18z Monday and into central Kansas by 00z Tuesday. With this more
eastward track, only the southeastern and far eastern Plains could
see some precipitation on Monday late morning into the evening, with
most of the precipitation falling east of our CWA. Both the ECMWF
and GFS forecast mixed precipitation between snow and rain, but
disagree on where exactly in the eastern Plains the snow will fall.
Ultimately, it will depend on how cold the temperatures can get
while the system moves through. If snow does fall, an accumulation
of less than an inch is expected.

As a new upper level trough moves in on Tuesday, models are still in
disagreement on the location and progression of it. As previously
discussed, the ECMWF has a closed low in central Arizona by 18z
Tuesday, while the GFS shows an upper level trough blending into a
storm system in the central United States. The CWA could see 0-2
inches of snow depending on the progression of the upper level low.
Regardless, temperatures will be colder.

By Wednesday, the upper level trough will travel eastward resulting
in northwest flow aloft. Due to a lack of moisture transport into
the region, precipitation chances are low.

&&

.AVIATION /06Z TAFS through 06Z Saturday/...
Issued at 1008 PM MST Thu Nov 14 2024

VFR conditions thru the period. Drainage winds overnight will
become more SW by 12z and then variable by 16z. A weak Denver
cyclone will be in place for Fri aftn. At this point it looks
like it will be SW of DIA which would allow for a east or
southeast component by early aftn. Later in the aftn winds
may switch to SSW if cyclone moves NW of DIA.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE.......RJK
SHORT TERM...Meier
LONG TERM....Ideker/JK
AVIATION...RPK