Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 220131

Area Forecast Discussion
National Weather Service Denver/Boulder CO
731 PM MDT SAT MAY 21 2016

Issued at 725 PM MDT Sat May 21 2016

Convection has refused to develop in our part of Colorado. This
was what the mesoscale models showed but when you have over 3000
cape in the northeast corner you expect something. There was a
fairly significant warm pocket on the evening sounding at 500 mb
that ensured there would be no convection. have reduce pops for
the remainder of the evening.

low clouds have persisted in the northeast corner...and the next
thing to look for with the high dewpoints will be the development
of fog. Like the day shift I believe it will stretch tonight from
eastern Larimer back to the northeast corner...but not down to DIA.
There is a Denver cyclone in place...on the east side of the
cyclone in eastern Denver dewpoints are in the mid 20s to around
30. On the northwest side of the cyclone dewpoints are in the
lower to mid 50s.

.SHORT TERM...(This evening through Sunday)
Issued at 333 PM MDT Sat May 21 2016

High resolution mesoscale models remain insistent that afternoon
convection will stay east of our forecast area, primarily in
Kansas. Indeed, the dew point temperatures as far east as Fort
Morgan and Limon have dropped into the lower 30s, while Akron`s
dew point is expected to fall from the current 61 degree reading
in the next hour or so. With the dry line evident over Yuma and
northern Washington Counties, any convective showers in Colorado
this evening should be confined to Logan, Sedgwick and Phillips
Counties. Have held on to isolated evening showers in case they
develop. The storms that do develop will be quite potent with CAPE
values of 2000-3000 j/kg over the northeast corner of the state.
Just enough capping at mid-levels will remain in place to keep
things in Colorado from getting to active.

The other location to get showers this evening will be the higher
terrain of Larimer County, where a few brief thunderstorms may
develop. After the evening convection dissipates, a lee trough of
low pressure will remain over northeast Colorado, and the
circulation around the surface feature will advect low level
moisture back into the region. Patchy fog is forecast to develop
from Logan County back into and across Weld County.

For Sunday, southwesterly flow aloft will continue, and another
dryline set-up is expected. Drying winds off the Palmer Divide
should once again push the threat of thunderstorms out to the
eastern border. Temperatures in the Denver area are expected to be
some 5 to 10 degrees cooler than today. There may also be a little
more shower activity over the mountains than we are seeing today.

.LONG TERM...(Sunday night through Saturday)
Issued at 333 PM MDT Sat May 21 2016

Deterministic models continue to show large scale troughing to
the west of Colorado and high amplitude ridging to our east on
Monday. Not until the latter half of the upcoming week do models
show this trough/ridge pattern shifting east. During the period
Monday-Wednesday the forecast area remains under the influence of
a relatively warm and dry swly flow with the possibility of a
weak mid-level pertabation passing over the area late in the day
Monday. Strong solar heating and the instability and lift
associated with this feature sufficient for scattered showers/
isolated t-storms in the high country and mainly isolated t-storms
on the plains. Although could see a bit more convection/t-storms
across the northeast corner of the state along a dry line/wind
shear bndry models straddling the area. Tuesday appears a bit
drier and warmer with only a few heat generated storms mtns and
plains late afternoon and evening. Temperatures both day expected
to run near average. Wednesday may end up being a repeat of Monday
with the passage of a weak mid- level disturbance carried along by
strengthening swly flow aloft. T-storm chances slightly better
esply on the plains late in the day along what looks like along
dry line/sfc trough bisecting the nern corner of the cwa.

For the Thursday-Saturday time frame...models show the upper
trough slowly progressing eastward over Colorado. GFS shows a more
organized and wetter system...the ECMWF a drier...slower and less
amplified system...while the Canadian model a faster... wetter and
cooler trough pattern. For now will rely on a blend of these and
other model guidance and introduce slightly higher precip chances
starting Thursday and a trend towards cooler temperatures. Best
chance for measurable precip/t-storms appears to be Thursday
according to the GFS. GFS also indicates some pretty impressive
qpf amounts. Whereas the ECMWF hardly and measurable precip until
Friday when it forms a closed upper low over northeast Colorado.
Will keep precip chances going through the weekend with reflect
this timing uncertainty.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 725 PM MDT Sat May 21 2016

Vfr conditions should persist tonight and sunday. There will be
some fog north of denver...and it should get close to the metro
area but we expect dia to remain fog free. On Sunday scattered
thunderstorms are expected over the mountains...and in the
afternoon isolated storms will drift across the plains...mostly
north of Denver.


.BOU Watches/Warnings/Advisories...


SHORT TERM...Dankers
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