Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 262002
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
202 PM MDT FRI AUG 26 2016

.SHORT TERM...(This evening through Saturday)
Issued at 133 PM MDT Fri Aug 26 2016

Challenging forecast today with the main branch of the upper level
trough still hanging out over Nevada bringing increasing westerly
flow over the state. A more diffuse trough is currently pushing
through the eastern plains with mid level forcing seen on water
vapor. This is helping to created scattered convection on the
plains. It appears the mountain and plains convection are driven
by two pieces of energy from the separate troughs with subsidence
between over the lower foothills and urban corridor. This will
help to keep storms at bay at least over the next few hours. Some
storms may come off the foothills and with dewpoints currently
hovering in the 40s to lower 50s cannot rule out a storm or two
over the Denver metro area. Main threats will be moderate
rain...lightning and gusty winds with the stronger storms. Some
graupal will be possible at higher elevations with a rain and snow
mix later this evening above 12000ft.

Overnight some showers may persist over the mountains as the
trough to the west will help to keep forcing over the area.
Elsewhere conditions will scatter out...especially over the
eastern plains as subsidence moves in. This will help to lower
overnight temperatures and create some areas of fog in the early
morning hours.

Tomorrow models have the upper trough firmly entrenched into
southern CA with weak SW flow aloft. Moisture is lingering around
and will be enough for a slight chance of storms in the mountains
by saturday afternoon. Temperatures will be slightly warmer with
highs reaching back into the 80s.

.LONG TERM...(Saturday night through Friday)
Issued at 133 PM MDT Fri Aug 26 2016

Saturday night into Sunday: Long range models are in agreement
that a mid and upper level short wave trough will be over the
lower Colorado River Valley (NV/AZ) on Sunday, placing Colorado
in a southwest flow pattern. The best synoptic scale vertical
lift associated with the trough remains across Arizona, New Mexico and
the extreme southern parts of Colorado on Sunday. Expect a few
thunderstorms to form in the mountains with the heating of the
day. Instability is limited east of the mountains so any storms
that form Sunday afternoon will have a hard time surviving as they
move over the Plains. Temperatures will warm into the mid 80s
across the Plains under mostly sunny skies, with afternoon clouds
via mountain convection spreading over the Plains through the late
evening hours. Mountains will warm into the 60s before isolated
thunderstorms form early afternoon.

Monday: The short wave trough remains disconnected from the
strong westerly flow across the northern U.S. and as a result does
not progress much. On Monday the trough should weaken and slide into
southern Arizona, reducing the synoptic scale lift across the
state. A robust mid and upper level ridge develops Monday and
continues to dominate Colorado weather through the week. Low
levels are dry on Monday with dewpoints in the mid 40s throughout
the Plains. PWATs remain below 0.75" for all but the far NE part
of the CWA.

Tuesday through Thursday: The mid and upper level ridge remains
in place and in fact build strength during the week because of
what is occurring upstream off the West Coast. An anomalously
strong long wave trough remains just off the West Coast, 3
standard deviations below normal for this time of year in that
region. The net result is a downstream ridge parked right over
Colorado with above normal temperatures and very low chances of
rain across the CWA. Can`t rule out isolated diurnal convection in
the mountains but the Plains should remain dry throughout the
remainder of the week. Temperatures across the Plains of Colorado
will be in the upper 80s to near 90, mountains will be in the mid
to upper 60s through Thursday. Will be watching the progression
(or not) of the anomalously deep/strong long wave trough along the
West Coast as it could become a player in Colorado`s weather late
next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 133 PM MDT Fri Aug 26 2016

Winds will start to transition to a ESE direction by 21z before
switching to drainage overnight. Storms will form over the
foothills but confidence is low it will make it over DIA before
daytime heating ends. Some gusty winds from outflows will be
possible between 04 and 07z. Winds will become light and variable
toward the end of the period. Ceilings will remain VFR until early
tomorrow between 14 and 16 where some stratus and low ceilings may
form. Do not anticipate fog affecting but BR lifting into a BKN
deck will be possible between 003 and 005.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...Schlatter
AVIATION...Bowen



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