Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 200300

Area Forecast Discussion
National Weather Service Denver/Boulder CO
900 PM MDT THU MAY 19 2016

Issued at 859 PM MDT Thu May 19 2016

Almost all of the convection has remained in the mountains and
foothills this evening, although there will still be a few light
showers attempting to drift onto the I-25 corridor through late
evening. Skies are already beginning to clear. There is another wave
of moisture as seen in satellite imagery over western Colorado and
eastern Utah but per current surface and radar obs moisture is
relatively starved with this one. Therefore, only a slight chance
of showers redeveloping over the higher mountains late tonight.
Rest of the forecast area will remain dry.

Other concern tonight is fog. Dewpoints were surging into the mid
to upper 40s over the plains. Continued moist south/southeasterly
flow will promote fog and stratus development along the
southeastern crest of the higher terrain from the Palmer Divide to
Limon and Akron overnight, with some stratus and fog also
expected to develop over Weld and eastern Larimer counties into
early Friday morning. Visibilities could drop to 1/4 mile or less.
Developing Denver cyclone could bring fog threat as far south as
the far northern Denver suburbs but relatively mild temps should
keep main threat farther north and east.


.SHORT TERM...(This evening through Friday)
Issued at 205 PM MDT Thu May 19 2016

Scattered showers and thunderstorms have at this point stayed over
the higher terrain due in part to large amounts of CIN over the
plains and calm transport winds. Models still indicate large CAPE
over the mountains and into the higher foothills. Most cells will
not move over the urban corridor as cells seem to die once they
move off the higher terrain...however satellite and short term
models show storms moving south out of Wyoming that could bring
rain...small hail...gusty winds and lightning. Cross sections
showing wet bulb zero temperatures getting down to 10k ft so light
snow showers will be mixed in at higher elevations. The main
threats with any storms on the plains will be light rain and
gusting winds up to 30 mph.

For tonight and into tomorrow...the upper ridge will continue to
build in with the surface low deepening on the lee side of the
mountains. Storms over the higher terrain will die off by 6 pm
with clearing on the plains. This clearing with continued
increased levels of moisture will bring another round of low lying
fog over central and southern Lincoln county tomorrow morning.
With the ridge moisture is more limited for Friday but there is
still a chance of scattered thunderstorms over the mountain with
CAPE values of 1000+ j/kg with a slight chance on the plains by
the late afternoon. The best CAPE will be on the far Eastern
plains. The main threats will be similar today with light to
moderate rain with PW values around 0.7 and gusty winds up to 40

.LONG TERM...(Friday night through Thursday)
Issued at 205 PM MDT Thu May 19 2016

Upper level low will be over the northwest part of the country
while a ridge resides over the central states. This will produce a
southwest flow aloft across Colorado through the weekend. For
Friday night, a few showers and thunderstorms may linger into the
early evening, otherwise it will be dry.

On Saturday, a surface low is progged to form over
Montana/Wyoming. In addition, southwest flow aloft will increase
as the upper ridge and low shift east. A south-southwest flow will
bring drier air into the area. There will be some moisture and
perhaps fog over the northeast corner during the morning. If
enough moisture hangs on, a few strong to severe storms will be
possible. Elsewhere, the drying airmass is expected to keep
convection isolated and weak. Saturday will be warm with many
locations topping 80 degrees across northeast Colorado.

A strong wave and cold front will move across the state Sunday.
This will provide lift, however moisture will be limited. Expect
scattered to isolated showers and storms Sunday afternoon and
evening. The best chance will be over the higher terrain. The
warmest temperatures will be found over the eastern plains where
the cold front will be last to push through.

For next week, troughiness will prevail over the western half of
the country. Flow aloft across Colorado will generally be
southwesterly and weak. A couple of waves embedded in the
southwest flow aloft will bring a better chance for showers and
storms, though it is too early to tell when this will occur. Will
broadbrush isolated/scattered pops during the afternoon and
evening hours. Temperatures will cool to near normal for early to
mid next week.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 859 PM MDT Thu May 19 2016

VFR conditions will persist through Friday, but there is a low
threat of fog at KDEN and KBJC 12Z-15Z Friday as Denver cyclone
develops late tonight into early Friday morning drawing higher
dewpoints into the area. At this time, any fog is expected to
remain along and north of a KFNL-KGXY line, and also farther south
and east toward KAKO and KLIC where visibilities could drop to 1/4
mile. About a 10-20% chance of high based thunderstorms after 21Z
Friday with around a 30% chance of gusty outflow winds.


.BOU Watches/Warnings/Advisories...


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