Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 302224
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
324 PM MST Wed Nov 30 2016

.SHORT TERM...(This evening through Thursday)
Issued at 246 PM MST Wed Nov 30 2016

Dry and cool air are in place over the state this afternoon with
weak upper level ridging also in place. Mostly clear conditions
will prevail overnight. A weak upper level disturbance will move
in from the west overnight...bringing increasing moisture and a
chance of snow to the mountains. Quasi-geostrophic diagnostics
shows only modest forcing with this system. Moisture amounts will
also be relatively low, so only light amounts of snowfall are
expected in the mountains, mainly through the day tomorrow.
Temperatures will be similar to the highs we saw today. Dry
weather should continue across the plains due to the general
westerly flow pattern that will be in place.

.LONG TERM...(Thursday night through Wednesday)
Issued at 246 PM MST Wed Nov 30 2016

Shortwave trough currently over the Pacific Northwest will drop
southward towards the Desert Southwest by Friday and then continue
on into Mexico where it will close off and stall over the
weekend. On its way south it will bring some moisture to the
mountains but no favored orographic flow of note so expect
generally light snowfall amounts from late Thursday through
Friday. East of the mountains moisture will be even more
limited...some weak upslope could develop by friday but at this
point snowfall chances look fairly low and did not change the
grids which had generally slight chance POPs. Best chance of some
snow accumulation east of the mountains would be south of Denver
up the Palmer Divide and also to the southwest. Temperatures
should be mainly in the 30s on the plains on Friday with more
cloudiness. Then milder over the weekend with the area between the
upper low well to our south and the next system that will be
approaching from the northwest. Did not see support for the snow
chances being so high in the mountains that came from the model
blend and lowered these over the weekend.

Model differences continue with the potential storm for next week.
The trough that eventually moves into the Rockies for Monday and
Tuesday is currently located in the mid Pacific. It will progress
eastward towards the Pacific Northwest and then drop into the
Rockies, similar to the much weaker system now there as the
overall pattern remains stable with a blocking pattern over
Canada. Much of the model differences have come in how the closed
low in Mexico evolves, with the GFS and some other models
consistent in leaving the closed low in place and then gradually
shifting it eastward while the ECMWF has waffled between a similar
solution to the GFS and one that is far more progressive and
phases the ejecting closed low with a northern wave. This was
quite pronounced in earlier runs of the ECMWF before changing more
to a GFS like solution yesterday, but then became more progressive
with last night`s run, with a corresponding more progressive
trough for Monday to Tuesday here. Now the 12z ECMWF is slower
again and as for the trough next week is also slower, with a
deeper system than the GFS that would also delay the main snow
until later Tuesday into Wednesday. This new solution was not part
of the model superblend so did some modification to at least keep
some chance of snow lingering into early Wednesday. Of course too
early to say just how significant this storm will be for us but
there is potential for a pretty decent snowfall for both the
mountains and plains. Much colder temperatures as well beginning
on Tuesday with the coldest air so far this fall.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 246 PM MST Wed Nov 30 2016

Skies are expected to remain mostly clear overnight as the dry
airmass stays in place. High clouds will increase tomorrow, but
no aviation impacts are expected. Winds will be light as pressure
gradients remain weak. Mountains will become obscured in clouds
and snow showers by tomorrow afternoon as a weak weather
disturbance moves over the western half of the state.


&&

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

$$

SHORT TERM...Dankers
LONG TERM...Szoke
AVIATION...Dankers


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