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fxus65 kbou 201502 

Area forecast discussion
National Weather Service Denver/Boulder Colorado
902 am MDT sun Oct 20 2019

issued at 902 am MDT sun Oct 20 2019

Web cameras and radar indicate snow is lingering in the mountains
this morning. Many higher mountain roads are still snow covered
and slippery. As snow decreases and roads thaw, conditions will
slowly improve through the day. Plan on keeping the Winter Weather
Advisory in effect until noon. Other issue today will be strong
west to northwest winds. Hrrr model over the past several runs has
been showing wind gusts of 50-60 kts over the northeast plains
this afternoon and early evening. Given the deepening low pressure
off to the northeast and strong winds aloft, this seems on track.
Will keep the High Wind Warning as is.


Short term...(today and tonight)
issued at 320 am MDT sun Oct 20 2019

Main concern today is the snow and strong winds
in the mountains today and the high wind potential in the
foothills and portions of the northeast plains by this afternoon.

The heavy snow band has already moved across the north central
mountains and Continental Divide area now with the most intense
snow diminishing before daybreak. Expect more lighter snow for the
rest of the day but winds will increase over the mountains with
gusts upwards of 50kt and plenty of blowing snow possible. Surface
cold front also rapidly spreading across the northeast plains with
gusts up to 40kt with the front.

A strong upper trof will intensify across Nebraska this afternoon
with very strong west and northwest winds mixing down to the
surface. Increasing subsident flow as qg Omega fields showing
anywhere from +30 to +70mb/hr of descent. Cross sections showing
45-50kt cross barrier flow developing this morning and through the
afternoon with just a hint of a critical later developing this
afternoon. Forecast soundings also look well mixed which would
help drive the 50-60kt down to the surface. Latest high
resolution models from hrrr/rap showing wind gusts around 65-75kt
developing over the Front Range foothills this morning around 15z
and up to 50kt over the plains this afternoon, especially from
locations north of a line from Fort Morgan to Akron, strongest
near the borders of Wyoming and Nebraska. The only negative for
high winds in the foothills would be the upstream moisture over
the mountains which may de-amplify the wave a bit. Still believe
the large scale subsidence will trump some of the local effects
and a strong enough signal to warrant high wind warnings for the
foothills and portions of northeast plains this afternoon.

Decent cold advection with this system as 700mb temperatures
plunge to around -7c today. This will put high temperatures this
afternoon only in the upper 40s and 50s across lower elevations.
There could be a few snow and rain showers across the far northern
plains this afternoon behind the intensifying upper low. Airmass
dries out tonight but there will be strong northwest flow and
lingering moisture embedded in the flow. This will keep the threat
of snow showers in the mountains but overall amounts should remain
on the light side.

Long term...(monday through saturday)
issued at 320 am MDT sun Oct 20 2019

In the wake of the fast exit of sunday's disturbance, cold
northwesterly flow aloft ensues across the state for Monday as the
edge of a 120-130 kt jet drives over northern and central
Colorado. Despite qg fields indicating strong mid and upper level
subsidence, forecast cross sections still hold on to mainly
orographically driven snowfall for the mountains through much of
the day with light amounts under highlight criteria. Out on the
plains for Monday, should be a windy day with cool steady
northwest flow at the surface. Frequent gusts above 25mph will be
expected through the day Monday, however no critical fire weather
concerns are expected at this time mainly due to the short window
of humidities in the 20s.

As an extensive ridge of high pressure continues to build over
the eastern Pacific and a deep trough slowly moves into the Great
Lakes region, a moist northwest flow aloft will persist over the
entire rockies, including northern Colorado, for Tuesday into
early Wednesday. With no discernible synoptic features in this
northwest pattern, the mountains should have windy conditions with
scattered light orographic snow showers each day. Temperatures
region wide will be slightly below the seasonal average each day
under this cool flow aloft.

As a weak short wave rides across the top of the Pacific Ridge
over British Columbia late Tuesday into Wednesday, the next
significant weather feature will be in the making for northern and
northeast Colorado. As this wave begins to phase with a trough
axis on the west edge of the Great Lakes trough Wednesday morning,
cold north-south meridional flow develops over southern Canada
and the northern US Great Plains in the form of a 130kt jet. This
wave will strengthen as it moves across the northern rockies of
Montana and eventually into northern Colorado. Out ahead of the
strongest winds aloft, a fairly strong surface cold front and
wind shift is expected to push onto the northeast plains Wednesday
afternoon. By 00z Thursday, forecast soundings indicate a quick
saturation of the column from surface to 400mb along with rapid
mid-level cooling of 7-10 degc by 06z Thursday in a low static
stability environment. A north to northeast surface wind component
is likely for late Wednesday into much of the day Thursday with
northerly flow up to 700mb in the soundings. At this time, can't
run away with the wintry features just yet as the latest run of
the qg fields indicate fairly weak ascent with this quick hitting
shot of potential wintry conditions. However, snow should be a
good bet for the high country along with the possibility for snow
over areas along the Front Range. A weather impacts focus will be on
the Wednesday evening and especially Thursday morning commuting
periods for urban areas for slow and difficult driving
conditions. Details on intensity and duration of snowfall will
become better apparent in later models runs.

By late Thursday into Friday, rapid drying accompanied with
strong subsidence is expected across the region as the axis from
the dominant Pacific Ridge edges to the central rockies. On it's
heels however is another fast moving trough riding southeastward
along the Canadian rockies. This may bring another cold front and
chance for precip for Saturday.


Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 902 am MDT sun Oct 20 2019

Strong west to northwest will prevail today. Wind gusts are
expected to approach 40 knots by 16z. Through the day winds will
turn north of due west, about 290-300 degrees. Wind gusts to 40-45
knots will remain possible through 00z. Winds will slowly
decrease this evening and eventually back to a drainage wind after


Fire weather...
issued at 320 am MDT sun Oct 20 2019

Critical fire conditions expected across the Palmer Divide this
afternoon with very windy conditions and low humidities. Could see
wind gusts 30-45 mph range this afternoon with blowing dust.
Humidities will be down towards 12 percent. Further north it will
be even windier on the plains but humidity levels will be
generally above 20 percent. No red flag warnings up north but high
wind warnings have been posted with gusts up to 65 mph possible.


Bou watches/warnings/advisories...
High Wind Warning until 7 PM MDT this evening for coz042>044-

High Wind Warning until 7 PM MDT this evening for coz035-036-038-

Winter Weather Advisory until noon MDT today for coz031-033-034.

Red flag warning until 8 PM MDT this evening for coz241-246-247.



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