Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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916
FXUS65 KBOU 191619
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
919 AM MST Fri Jan 19 2018

.UPDATE...
Issued at 905 AM MST Fri Jan 19 2018

Considerable wave cloudiness persists over the Front Range and
plains this morning and appears this may hold in for much of the
day given the moisture still upstream over Nevada and Utah. Given
thickness of cloud deck, this may hold temperatures down a bit at
least through early afternoon. With the stronger west and
southwest flow aloft, there will be some gusty winds over the
higher peaks and exposed east slopes through this afternoon.
Observations are in the 30-45 mph range and some higher gusts up
to 65 mph over peaks, including Berthoud Pass. Will update
forecasts to match observational patterns this morning.

&&

.SHORT TERM...(Today and tonight)
Issued at 356 AM MST Fri Jan 19 2018

Upper ridge will be moving east of Colorado today with westerly
flow aloft increasing a bit. The warmest air aloft will be
shifting east of Colorado, but with a warmer start and weaker low
level inversions, the increased mixing should still produce warmer
highs this afternoon. The stronger flow aloft will produce
pressure falls over eastern Colorado and there will be a battle
between the warm west winds mixing off the foothills and not as
warm air in south to southeast winds over the plains. Given the
weakness of the inversions though, I expect the warmer air to push
across most of the Front Range cities, with places like Greeley
and Limon possibly on the edge of the warmer air. It also looks
like there should be some decrease in the amount or at least the
thickness of the high cloudiness during the day. Denver should be
near its record high of 68 this afternoon.

For tonight, high clouds should thicken again from the west as the
upstream trough approaches. This should bring another mild night.
Models have appeared a bit too high with the mid level moisture
into the mountains, but the real deeper moisture will be
approaching the Rabbit Ears pass area by Saturday morning, so a
slight chance of snow showers in that area late tonight looks
good.

.LONG TERM...(Saturday through Thursday)
Issued at 356 AM MST Fri Jan 19 2018

Increasing SW flow aloft will be over the area on Sat in advance
of a storm system. Sfc low pres will be over ecntrl CO, however,
it will move into sern CO by aftn and allow for a cold front to
move across the plains.

Overall, cross-sections show best moisture and QG ascent will
hold off until Sat night, so most pcpn will be confined to zone
31 thru the aftn hours with dry conditions over nern CO. As for
highs, readings across the plains will range from the lower to mid
40s near the WY-CO border with lower 60`s across Lincoln county.

By Sat night an upper level low will develop near the Four Corners
area, which will move into sern CO by midday Sun and then into wrn
Kansas by Sun evening.

Cross-sections show moisture increasing across the area Sat night
into Sun along with favorable QG ascent.  Low level winds fields
currently are fcst to be more Northerly than Northeastly which could
end up focusing heavier pcpn away fm the Foothills and across the
plains.  However, experience with these type of systems suggest
models may have low level flow to northerly but time will tell. Pcpn
generated fm QG fields is pretty decent across much of the area late
Sat night thru Sun. In addition there could be some heavier banded
pcpn in association with upper level jet Sat night into early Sun.

At this point advisory amounts are a good bet across all of the
area, however, confidence of warning criteria isn`t as high since
since the majority of snow across the plains will occur on Sun.
For now will let the day shift see another model run before
issuing any watches for nern CO.

By Sun night the storm system will move eastward into the central
plains with snow gradually ending over the far ern plains by
midnight.  On Mon drier air in WNW flow aloft will move into the
area with only a slight chc of snow showers in the mtns.
Temperatures will be near seasonal levels.

For Tue into Wed the flow aloft will become more WLY.  The GFS has
quite a bit of moisture embedded in the flow on Tue while the ECMWF
is drier.  On Wed both models show very little moisture embedded in
the flow. For now will just keep a slight chc of snow in the mtns
with dry conditions elsewhere.  Temperatures will remain near
seasonal levels on Tue and then begin to moderate some on Wed.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 905 AM MST Fri Jan 19 2018

Considerable high level moisture will remain over terminals with
mountain wave cloudiness through mid afternoon, with some
thinning out by this evening. Winds will vary in the south to
southwest direction through tonight with an occasional stronger
gusts up to 18kt at APA.

&&

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

$$

UPDATE...Entrekin
SHORT TERM...Gimmestad
LONG TERM...RPK
AVIATION...Entrekin



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