Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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295
FXUS65 KBOU 281635
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1035 AM MDT SUN AUG 28 2016

.UPDATE...
Issued at 1034 AM MDT Sun Aug 28 2016

This mornings cloud cover and showers over the plains have
decreased as expected while showers continue over the central
mountains and high valleys. As the upper low continues to spin
near the four corners area, lift over the forecast area will
increase through the day, especially over the southern
half...mainly south of I76. High surface pressure over the plains
will push in upslope winds through 700 mb by the afternoon while
divergence occurs aloft. Have increased the chance of
showers/storms over the high terrain and foothills south of I70
and the Palmer Divide this afternoon. Areas north of this,
especially closer to the northern state border look to remain more
stable. Best chance for storms over the southern urban corridor
seems to be after 2pm and into the early evening, with chances
remaining after midnight east over the plains. Comparing forecast
soundings to yesterday...weak shear and higher freezing levels
will keep hail hazard to small hail and gusty outflow winds to 45
mph will be possible.

&&

.SHORT TERM...(Today and tonight)
Issued at 325 AM MDT Sun Aug 28 2016

An upper level low over northern Arizona will slowly move east
through the next 24 hours and be over northwest New Mexico 12z
Monday morning. A wave ahead of the low is producing mid and high
clouds over eastern Colorado. Some of the models show a few
showers and storms associated with this system this morning. Will
have low pops in the forecast for southern parts of the Front
Range.

Should see some clearing behind this wave late this morning and
early afternoon. Expect temperatures to be a few degrees warmer
today with highs mainly in the mid to upper 80s over northeast
Colorado. Precipitable water values will increase today with
values around a half inch over the mountains to an inch over the
eastern plains. CAPE will also increase today with values
climbing to 800 J/kg. The best instability will be found over the
eastern plains and higher terrain. Will have to the highest pops,
30-40 percent here. Main threats with the storms will be brief
heavy rain, small hail and wind gusts to 40 mph.

Expect most of the convection to end by mid to late evening as the
airmass stabilizes. However, could see a few weak showers and
storms linger past midnight as the upper level low moves closer.

.LONG TERM...(Monday through Saturday)
Issued at 325 AM MDT Sun Aug 28 2016

Monday into Tuesday a broad upper level ridge of high pressure
will stretch across the central and southern u.s. A weak
south/southwesterly flow aloft will be over CO. Subtropical
moisture will continue to sit across eastern CO...and sufficient
enough to produce a round of aftn/evng tstms both days...some of
those storms may linger overnight along the CO/KS borders.
Wednesday into Thursday...the ridge axis shifts a bit more to the
east which will allow the plume of subtropical moisture to shift
eastward as well. Still the potential for aftn/evng tstms but
coverage will be lower and temperatures will warm up as well. The
flow aloft will remain weak into next weekend with a persistent
southwesterly flow aloft. Subtropical moisture will still be
around but GFS/ECMWF suggests the overall coverage will more
isolated by late in the week and into the weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday morning)
Issued at 1034 AM MDT Sun Aug 28 2016

Mid and high clouds will be increasing towards 18z with a chance
for thunderstorms this afternoon, especially to airports from
Denver south. Best chance of thunderstorms from 22z-03z. A
somewhat moist airmass will keep mid and high clouds over the area
through the night. Northwest winds will end up northeast to east
this afternoon. Wind speeds will be on the light side, generally
less than 10 knots. High res models show convective activity
pushing north from the Palmer Divide after 21z which may produce
southerly winds for an hour or two, then there seems to be a
westerly component after 00z for a couple hours as well. Have
included this in KDEN TAF...want to see how this afternoons
convection plays out before adding into all TAFs. Drainage winds
overnight will become easterly again Monday.


&&

.BOU Watches/Warnings/Advisories...
None.
&&

$$

UPDATE...Kriederman
SHORT TERM...Meier
LONG TERM...Cooper
AVIATION...Kriederman



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