Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 190156
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
756 PM MDT Thu Apr 18 2019

.UPDATE...
Issued at 756 PM MDT Thu Apr 18 2019

Winds have decreased some over the eastern plains and will
continue to decrease through the evening. Current forecast appears
on track. Only changes will be to line up with current trends.

&&

.SHORT TERM...(This evening through Friday)
Issued at 330 PM MDT Thu Apr 18 2019

Drier air is working in from the north now. There is
still quite a bit of weak convection but this will decrease with the
drying and cooling this evening. Mountain snow showers also look to
be decreasing quickly with the drying. The low level pressure
gradient is also diminishing, though mixing will keep winds up the
rest of the afternoon. These to should diminish sharply in the early
evening, though there will still be some wind over the higher
mountains and on the eastern part of the plains.

The forecast for tonight and Friday looks in good shape, with warmer
and drier air moving in and weakening northwest winds aloft.
Forecast temperatures are near guidance and will be about 15 degrees
warmer for highs on Friday. Humidities will be low with afternoon
breezes in some areas, but not Red Flag criteria, and most places
have green fuels now anyway.

.LONG TERM...(Friday night through Thursday)
Issued at 330 PM MDT Thu Apr 18 2019

Mid to upper level ridging will be over Colorado Friday night into
Saturday morning before a weak trough begins to break down the
ridge Saturday evening. Generally light, downslope winds
throughout the day Saturday will allow temperatures to warm well
above normal with a chance that Denver reaches 80 degrees.
Soundings indicate convective temperatures will be in the upper
70s and with the strong morning sunshine, it is expected these
temperatures will be reached. Therefore, scattered high-based
rain showers will develop during the afternoon but most of the
moisture from these showers will evaporate before it reaches the
surface. I expect these showers to create some gusty winds up to
35 mph as the pockets of rain-cooled air underneath the showers
will accelerate toward the surface.

A cold front will move southward out of Wyoming and Nebraska
on Sunday bringing more moisture and cooler air to northeast
Colorado. At the same time, a trough with relatively cool mid to
upper level air will move eastward toward the Four Corners area.
The phasing of the low level moisture and upslope flow with the
ascent from the approaching trough will create widespread
precipitation across north-central and northeast Colorado Sunday
afternoon through most of the day Monday. With precipitable water
values near 0.8" and weak mean flow, these showers will produce
moderate to briefly heavy rain showers over the plains and snow
showers in the mountains. In addition, thunderstorms over the
plains will have the potential to produce small hail Sunday
evening due to good lapse rates and weak instability. It is not
out of the question that a couple storms over the Palmer Divide
could see severe hail as that area will have the best instability
with CAPE values between 1000-2000 j/kg and will be closest to the
mid to upper level jet streak which will allow for the best deep
layer shear.

Those expecting to travel in the mountains this holiday weekend will
likely see hazardous travel conditions by Sunday night with the
moderate to heavy snow with the worst conditions across the
northern Front Range. On Monday, I lowered high temperatures as
low clouds and showers will persist throughout much of the day.
The intensity of these showers should be much lighter than on
Sunday.

Models begin to differ greatly by Wednesday. The GFS and Canadian
are more progressive with the trough that affects Colorado on
Sunday and Monday with a ridge building over Colorado by
Wednesday. However, the Euro has the trough cutting off and
sagging southward toward Texas on Wednesday and Thursday.
Considering the trough of interest is still over the Pacific
Ocean at this current time, there is low confidence in the
forecast during this period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 756 PM MDT Thu Apr 18 2019

Winds will continue to decrease and turn clockwise ending up a
southerly direction by 04Z. There is uncertainty on wind direction
Friday morning. Expect winds become northwest and then north to
northeast after 18z. Winds speeds should be light Friday, mainly
less than 10 knots.

&&

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

$$

UPDATE...Meier
SHORT TERM...Gimmestad
LONG TERM...Danielson
AVIATION...Meier


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