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000
FXUS65 KBOU 190938
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
338 AM MDT Sat May 19 2018

.SHORT TERM...(Today and tonight)
Issued at 338 AM MDT Sat May 19 2018

Radar trends and models indicate an upper level low will stall
over northeast Colorado this morning and then slowly weaken and
move off to the east by early evening. Based on radar and reports,
estimate that 1-2 inches of rain has fallen over north central
Weld, Morgan, western Logan, and northern Washington counties.
Rain is expected to persist much of the day north of a line from
Briggsdale to Fort Morgan to Akron. This area will need to be
monitored for flooding since up to 2 more inches of rain is
expected through this afternoon. Will continue with the Flash
Flood Watch for these areas.

It is uncertain how far west precipitation will make it today.
Many of the 00Z model runs show the rain making it to the base of
the foothills and into the Denver area. However, the few 06Z
models in so far now keep most of the rain where it is with little
west/southwest progression. Looking at radar trends, believe this
is a reasonable solution. Cold air advection will occur over
northeast Colorado due to northerly winds on the back side of the
low. This is helping low clouds form at this time. Expect clouds
to lower more through the morning. Best chance for precipitation
along the Front Range and in the Denver may come in the form of
drizzle. Temperatures are expected to remain steady in the upper
40s to lower 50s today due to cloud cover.

Rain associated with the upper level low is expected to stay east
of the higher foothills and mountains. Cold air aloft will help
destabilize the airmass this afternoon. Isolated to scattered
showers and thunderstorms will be possible. Will cancel the Winter
Weather Advisory for the mountains since widespread snow is no
longer expected.

For tonight, rain is expected to end this evening as the low
weakens and exits the area. Low clouds will linger through the
night and could see some drizzle and fog in places. Temperatures
will be chilly with readings in the lower 40s expected.

.LONG TERM...(Sunday through Friday)
Issued at 338 AM MDT Sat May 19 2018

On Sun the flow aloft will become more WSW as a weak disturbance
moves across late in the aftn into Sun evening. MLCAPE values
are around 500 j/kg over the higher terrain with very little CAPE
over nern CO. Thus best chc of showers and storms will be over
the higher terrain with some of the activity possibly affecting
the front range urban corridor. As for highs, readings will rise
into the 60s across the plains.

For Mon an upper level low will develop over srn California with
WSW flow aloft remaining over nrn CO. Meanwhile a weak sfc lee
trough will develop along the front range. This should allow for
deeper low level moisture to gradually increase over the plains.
So expect better instability by aftn with MLCAPEs in the 500-1000
j/kg range. Overall will keep in a chc of storms in the mtns with
a slight chc across nern CO. Temps will continue to rise as
readings reach the 75 to 80 degree range over the plains.

By Tue the upper level low will begin to move north into Nevada
with the flow aloft becoming more SSW across nrn CO. There will
still be favorable CAPE across portions of the plains so will keep
in a slight chc of storms. Over the higher terrain there will
still be enough moisture for a chc of storms as well. Highs across
nern CO will continue to warm as readings rise into the lower to
mid 80s.

On Wed the upper level low will continue to move basically northward
into the nrn Rockies as SSW flow aloft remains over the area.
Some drier air may spread across the area which could reduce the
chc of storms over the higher terrain. Over nern CO will keep pops
mainly in the slight chc category. Highs on Wed will be similar
to Tue.

By Thu the upper level low will move across the nrn Rockies with the
flow aloft becoming more SW.  Once again there is limited moisture
over the higher terrain so will keep pops on the low side.  Across
nern CO there should still be decent instability across portions of
the plains so will keep in a slight chc of storms.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 338 AM MDT Sat May 19 2018

Low clouds with ceilings of 500 to 2500 feet are expected to
persist through 12Z Sunday. There is a chance for ceilings below
500 feet and visibility down to the quarter mile between 12Z and
18Z today due to fog and rain showers. North to northwest winds
will prevail today with gusts to 25 knots possible after 12Z. Rain
showers are expected to end across the area by early evening.
However, low clouds should linger through Sunday morning. Could
also see fog with quarter mile visibility after 06Z Sunday.

&&

.HYDROLOGY...
Issued at 338 AM MDT Sat May 19 2018

Rain will continue over northeast Colorado for most of today.
Areas north of a line from Briggsdale to Fort Morgan to Akron have
received 1 to 2 inches of rain. An additional 1 to 2 inches of
rain is expected today. This may cause flooding of low lying and
poor drainage areas. Fortunately, rainfall rates will be less than
a half per hour, so significant flooding is not expected. Will
keep the Flash Flood Watch in effect for the above mentioned
places. Elsewhere, will cancel it since only light rainfall is
expected.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through this afternoon for COZ042-044-048>051.
&&

$$

SHORT TERM...Meier
LONG TERM...RPK
AVIATION...Meier
HYDROLOGY...Meier