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Area forecast discussion 
National Weather Service Denver/Boulder Colorado
315 PM MST sun Feb 1 2015

Short term...(this evening through monday)
issued at 129 PM MST sun Feb 1 2015

Radar and satellite pictures show a mostly clear County Warning Area right now.
The exception being a pesky area of stratus and even some light
snow over the greater Denver metropolitan area...the eastern parts of
Adams and Arapahoe...and all of Douglas and Elbert counties. The
plains still have upsloping low level winds. Models have north-
northwesterly flow aloft this evening then it becomes northwesterly
overnight...and west-northwesterly by Monday afternoon. Speeds are
60 to 90 knots at jet level for both periods. The qg vertical
velocity fields show downward synoptic scale energy for the County Warning Area
tonight and Monday. The boundary layer flow will be a combination
of normal drainage and southwesterly downsloping tonight.
Downsloping west-northwesterlies are prognosticated on Monday. For
moisture...the plains dry out this evening...with increasing
moisture for the mountains. Overnight...moisture gets pretty deep
in the mountains...with some upper and middle level cloudiness for
the plains. By 00z Monday late afternoon...there is low and middle
level moisture in the mountains and some in the middle levels for the
eastern plains. The quantitative precipitation forecast fields have nothing this evening...then a
tad of measurable snow overnight and Monday for the mountains. For
probability of precipitation...will have all the plains dry tonight and Monday. For the
mountains...the moisture is on the way...and the satellite
pictures agree with the cross sections on that. So will go with
30-60%s from midnight tonight through Monday. Amounts will not be
great even though there is the moisture and decent orographic
help. There is pretty decent warm air advection...so that will
counter act the moisture and wind somewhat. Concerning winds...
cross sections show a mountain wave set up developing this
evening and continuing into early Monday afternoon. The best
looking wave is on the NAM. Speeds look to be below highlight
criteria. For temperatures...there is warm advection tonight and
Monday. Monday's highs are up 7-14 c from this afternoon's
readings.

Long term...(monday night through sunday)
issued at 129 PM MST sun Feb 1 2015

Monday night not Tuesday...a strong northwesterly flow aloft will
continue remain over Colorado. Nam12 spatial cross-sections
indicate the moisture deepening over the mountains on Tuesday so
will go with likely probability of precipitation...especially along the west facing slopes.
Mainly light snow but gusty winds above timberline will produce
areas of blowing snow. The mountain wave itself is not very well
developed Monday night so suspect stronger winds will remain in
the higher east facing slopes. Downslope/prefrontal winds will make
for another mild day on Tuesday. Tuesday night into Wednesday...
a strong upper jet overrides the ridge to the west and slides
across northern Colorado. The GFS/European model (ecmwf) both develop snow in the
mountains and then spread it eastward across the foothills and
plains. It appears there could be some banded snowfall developing
with the passage of the upper jet. At this time...highest probability of precipitation will
favor the northern tier zones. A front does slide down into Denver
in the afternoon...with shallow but fairly strong upslope for a brief
time. As a result...could see a brief period of moderate to heavy
snow with the passage of the cold front. At this time...all of
this will only translate to a chance in the grids but it does bear
watching. For the rest of the period...dry and warmer for the rest
of the week and into the weekend. Not much moisture apparent at
this time but will go with slight chance probability of precipitation in the mountains by the
weekend.

&&

Aviation...(for the tafs through 00z Monday late afternoon)
issued at 129 PM MST sun Feb 1 2015

The low stratus has hung on over the Airport all day. Satellite
pictures show it eroding away and hopefully it will be done by
00/01z. The expected enhanced drainage/downsloping
southwesterlies should kick in early this even and assure the
ceilings to be gone. There will be no ceiling issues after
01/02z. Drainage winds tonight and downsloping westerlies on
Monday. Speeds do look to exceed 15 knots.

&&

Bou watches/warnings/advisories...
none.
&&

$$

Short term...rjk
long term...Cooper
aviation...rjk

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