Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS65 KBOU 212133

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

.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 18Z TAFS through 18Z Sunday afternoon)
Issued at 333 PM MDT Sat May 21 2016

Southeast winds will continue this evening and then return to more
southerly overnight. No showers are expected across the Denver
area. The fog and stratus that are expected to develop over Weld
County after midnight may move into the KDEN area during the early
morning hours. This may produce a couple hours of IFR conditions
from about 6 AM through 9 or 10 AM.


.BOU Watches/Warnings/Advisories...


SHORT TERM...Dankers
AVIATION...Dankers is the U.S. government's official web portal to all federal, state and local government web resources and services.