Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 291638

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1038 AM MDT SUN MAY 29 2016

Issued at 1018 AM MDT Sun May 29 2016

A weak west/southwesterly flow today ahead of an upper low over
southern CA. Some weak mid level qg ascent stretching fm NM into
the OK panhandle. Latest HRRR initially develops some tstms over
the Palmer Divide and Cheyenne Ridge after 19z...then the rest of
the cwa fills in with generally weak thunderstorms east of a New
Raymer to Watkins line. Most the storm will produce brief light to
moderate rainfall...wind gusts to 35-40 mph and cloud to ground
lightning. There may be less tstm coverage over the mountains. I
may lower the coverage just a little bit there... otherwise the
rest of the grids are fine.


.SHORT TERM...(Today and tonight)
Issued at 351 AM MDT Sun May 29 2016

Westerly flow aloft will become southerly later today and tonight
as an upper level low moves across southern California. Water
vapor satellite imagery is showing a weak short wave trough over
southwest New Mexico. Models show this wave lifting northeast
through the day. This wave may help trigger storms over southern
parts of the area. Airmass becomes unstable again this afternoon
with CAPE values up to 1000 J/kg. Could see slightly higher values
over the eastern plains if more moisture advects into the area.
Overall, expect similar thunderstorm coverage as yesterday, mainly
scattered storms. There will be a little better chance for hail
with the storms today because of the increased CAPE. However CAPE
and shear will be on lower side, so not expecting severe storms.
However, can`t rule out one or two storms just reaching severe
threshold over the eastern plains. As far as temperatures go,
highs will be 2 to 6 degrees warmer today.

.LONG TERM...(Monday through Saturday)
Issued at 351 AM MDT Sun May 29 2016

Low amplitude upper level ridge shifts east of Colorado on Monday
allowing a long wave upper trough to pass over the region Monday
night and Tuesday. The closed low associated with this trough over
western Arizona is forecast to weaken as it tracks slowly
southeast towards the U.S./Mexico border...while the upper low
over western Montana is projected to gain strength as its drops
southeast clipping nern Wyoming along the way. Monday should start
out dry and mild across the CWA with near zonal flow aloft. Then
as temperatures quickly warm should see scattered showers/t-storms
blossoming over the high terrain around midday. Should see some
of this convection carried off the Front Range during the
afternoon tied to a weak disturbance embedded in the wly flow
aloft. By evening could see some intensification in these t-storms
as they advance into higher dewpts and steeper lapse rates across
far eastern sections of the CWA. Cannot rule out a few hail and
heavy rain producers in this area during the evening hours.

As the northern low passes to our north Monday night...northerly
flow on its back side drives a cold front through nern Colorado
during the pre-dawn hours. Synoptic scale forcing for ascent
appears weak with the upper trough...however during the day
Tuesday models show a deepening northeasterly/upslope flow on the
plains producing a heavy cloud cover and cooler temperatures as
well as areas of light precip. Most of this showery precip is
expected to fall east of the Continental Divide late Monday night
and much of Tuesday with 12-hour precip totals generally a
quarter inch or less. Could see locally heavier amounts in the
foothills to the west and southwest of Denver. Farther out on the
plains...amounts anywhere from a trace to a tenth of an inch.
High temperatures go from around average on Monday to as much as
10-12 degs f below average on Tuesday...with the greatest cooling
likely to occur east of the Cont Dvd.

Tuesday night and beyond...the upper trough shifts over the
northern Great Plains allowing an upper level ridge to gain
strength over the Great Basin. Models show this building ridge
with its warmer temperatures and drier air migrating eastward over
Colorado by Friday. Should see a significant reduction in cloud
cover and limited chances for showers/t-storms with its arrival.
Guidance indicates highs both days in the low to mid-80s on the
plains of northeast Colorado.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1018 AM MDT Sun May 29 2016

Scattered thunderstorms are expected to form over the higher
terrain...especially to the south/southwest of Denver...then
spread east/northeast through the afternoon and evening. Best time
for thunderstorms in the Denver area is 21z-01z. Will go with vcts
in the grids this aftn at kden and kbjc and ocnl ts to the kapa
taf. The storms will be capable brief light to moderate rainfall
and wind gusts to 35 knots. The latest HRRR keeps the wind less
than 10 kts but transitions it to nnely by midday...then more
east/southeasterly by mid afternoon. outflow winds will disrupt
this wind pattern in the 20-01z window. Will keep vfr cig/vsby
conditions prevailing through the period.


.BOU Watches/Warnings/Advisories...


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