Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 201733
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1133 AM MDT Sun May 20 2018

.UPDATE...
Issued at 1121 AM MDT Sun May 20 2018

The low cloud deck is slow in dissipated this morning. The
drizzle and fog have ended at present. Will adjust some sky cover
in the GFE. Pops are on track with most of the plains the plains
to cool and stable fro convection.

&&

.SHORT TERM...(Today and tonight)
Issued at 330 AM MDT Sun May 20 2018

Water vapor satellite imagery showing a short wave trough
spinning over northwest Arizona and southern Nevada. Models lift
this wave northeast across Utah and western Colorado. This is
expected to trigger isolated to scattered thunderstorms over the
western and central Colorado mountains this afternoon.

East of the mountains, along the Front Range and across the
eastern plains, it will be a cool and cloudy morning as the upper
level system that brought rain to the state exits the region.
Easterly surface winds around a surface high over the Central
Plains will help keep cloud cover through mid to late morning.
Because of this easterly upslope slope, drizzle will also be
possible in and near the foothills. The sun will come out late
this morning and bring some warming. Highs will be cool still with
readings in the 60s. Mid and high clouds will increase late this
afternoon due to convection over the mountains. There will be a
slight chance a few off these move off the higher terrain. If they
do, they won`t last long because of the stable airmass over the
plains. Best chance for storms moving off the mountains will be
the higher terrain south of Denver. These storms will be weak with
brief moderate to heavy rain. Small hail will also be possible
with the storms, mainly over the mountains.

.LONG TERM...(Monday through Saturday)
Issued at 330 AM MDT Sun May 20 2018

An upper level low will be over srn California on Mon and then will
begin to lift north northeast into Nevada by Tue.  This will allow
for southwest flow aloft across the area.  There will be some
moisture embedded in the flow which will combine with favorable
lapse rates to produce a chc of aftn showers and tstms both days
over the higher terrain.  Over nern CO there will be enough
instability for some aftn/evening tstms both days, however, not
certain about coverage so will keep pops in the slight chc category.
As for highs, readings will be in the upper 70s to lower 80s on Mon
and then in the lower to mid 80s by Tue across the plains.

On Wed the upper level low will weaken as it moves into Montana,
however, the flow aloft will remain southwesterly.  Some drier air
will move into the area so tstm chances will decrease over the
higher terrain.  Over nern CO there still will be some decent
instability especially over the far nern corner so will keep in some
low pops for late aftn/evening tstms.  Highs will remain above
normal with readings in the 80s across the plains.

By Thu the flow aloft will become more westerly with cross-sections
still showing limited moisture over the higher terrain so will only
mention a slight chc of aftn storms.  Across nern CO once again
enough instability will exist to keep in isold/wdly sct
aftn/evening tstms as highs remain around 10 degrees above normal.

On Fri the flow aloft will become more northwest as an upper level
trough moves across the nrn and central US.  Once again there isn`t
much moisture over the higher terrain so will keep pops on the low
side. Over nern CO will keep in isold to widely sct tstms in the
aftn/evening with little change in high temperatures.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1121 AM MDT Sun May 20 2018

Models keep weak easterly flow at DIA well into this evening,
then they allow for pretty normal drainage winds to kick in
around 04Z-06Z. The Stratus deck is slow in eroding this morning.
Now models show it getting above BKN060 by late afternoon. I
doubt there will be an precipitation at DIA for the rest of
today.


&&

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

$$

UPDATE.......RJK
SHORT TERM...Meier
LONG TERM....RPK
AVIATION.....RJK



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