FXUS65 KBOU 190341

Area Forecast Discussion
National Weather Service Denver/Boulder CO
941 PM MDT Mon Mar 18 2019

Issued at 940 PM MDT Mon Mar 18 2019

The radar is show a couple of areas of light showers right now;
one area across the southern CWA, the other across southern Weld
and northern Morgan Counties. There is little to no precipitation
hitting the ground. There is still a decent batch of cloudiness
upstream to move across the CWA in the western flow aloft. You can
also see an upper trough moving southward out of Montana
currently on the water vapor satellite pictures. Will make to
changes to the pop, weather and sky grids based on reality.


.SHORT TERM...(This evening through Tuesday)
Issued at 258 PM MDT Mon Mar 18 2019

An upper trough over the Dakotas and back into Wyoming will be
reinforced tonight by a second shortwave trough dropping south
from Canada. Some instability and added moisture ahead of this
feature will allow some showers over the higher terrain, as well
as near the Palmer Divide this afternoon into the early evening.
May hear a rumble of thunder or two over the high terrain of South
Park as well this afternoon. The reinforced trough will push a
cold front down over the forecast area this evening, lowering
clouds and potentially producing a few light snow showers,
especially out east over the far eastern plains where QG lift will
be stronger. Some snow showers will continue over the mountains
in the favored northwest flow aloft.

The upper trough axis will push over the area on Tuesday with high
surface pressure slipping down from eastern Montana down to
northern Nebraska. This will turn surface winds more upslope to
hold in the low clouds over most of the area and produce snow
over the high terrain, foothills and the Palmer Divide. Expected snow
amounts will be a trace to two inches. There will be a chance for
some snow showers to form further east over the Denver metro area
in the afternoon, but less than half an inch is expected as
moisture will be less and high temperatures will be in the upper
30s to near 40. Winds over the easterly plains will be gusty out
of the north-northwest with speeds of 10-20 mph.

.LONG TERM...(Tuesday night through Monday)
Issued at 258 PM MDT Mon Mar 18 2019

An upper level trough will move southeast of nern CO Tue evening.
Cross-sections show rather limited moisture with this feature,
however, can't rule out some showers over the higher terrain south
of I-70, and across the Palmer Divide early in the evening.

For Wed into Thu a blocking pattern will be in place as an upper
level high resides over the nrn Rockies. This will allow for an
upper level low to develop over the swrn US by Thu. Overall expect
dry conditions with seasonal temps both Wed and Thu. Some moisture
could eventually move north northeast from Arizona and New Mexico
into swrn areas late in the day so will keep in a slight chc of
showers over the higher terrain.

From Thu night into Fri the upper level low is fcst to move into the
four corners area. This will produce southerly flow aloft across
the area. Combination of QG ascent, increasing moisture and
favorable lapse rates would lead to a better chc of showers and even
a few tstms especially on Fri. Meanwhile with no front affecting
the area temps will remain near seasonal levels with any snow
confined mostly to the mtns.

By Fri night into Sat there isn't much agreement between the ECMWF
and GFS. The ECMWF has one piece of energy lifting north into srn
WY while a 2nd piece of energy moves into sern CO. Meanwhile the
GFS moves the main upper level into central WY. Overall, neither
solution would lead to a widespread pcpn event over the area.
However, with steep lapse rates and available moisture, there would
still be a chc of showers and a few tstms especially in the aftn and
evening hours. Meanwhile, the OOZ run of the ECMWF and some of the
GFS Ensemble Members have a more consolidated system ending up
further south on Sat across cntrl or srn CO. If this were to occur
then pcpn chances and amounts would be higher. Suffice to say
there is still a lot of uncertainty regarding how things will
evolve late in the week.

For Sun the ECMWF has another upper level trough moving eastward
into the area while the GFS has a flat upper level ridge. Not sure
what to believe at this point since it's not obvious how the first
upper level trough will act. Thus will just go with the blended
solution for now and keep a chc of showers in the mtns with dry
conditions over nern CO.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 940 PM MDT Mon Mar 18 2019

Models show weakening north and northwesterly low level winds at
DIA all night. Not sure is the normal drainage winds will ever
get in there overnight. Some low level moisture looks possible
according to the new 00Z model cross section. Current TAFs show
some SCT-BKN030-040 overnight into Tuesday morning. May keep
something like that going in the new 06Z TAFs. Do not think there
will be any showers at DIA tonight, but will leave the VCSH in for
Tuesday afternoon.



SHORT TERM...Kriederman
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