Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 210128
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
728 PM MDT FRI MAY 20 2016

.UPDATE...
Issued at 728 PM MDT Fri May 20 2016

Only isolated showers were able to briefly push through the
cirrus shield over the forecast area this afternoon, and those
have all dissipated. 00Z soundings from Denver and Grand Junction
show a stable layer, more pronounced on the Grand Junction
sounding. The cap is expected to remain in place through the rest
of the night so no further storm threat.

The eastern plains will see another round of low clouds and
fog, and even some drizzle overnight as moisture continues to
increase in stronger southeast flow. The low clouds and fog may
wrap back as far as the northern sections of Denver by early
Saturday morning with the aid of a Denver cyclone, but main threat
would be from northern Larimer and Weld counties east and
southeast to around Akron, Limon, and points east. Overall
forecast on track, just removed evening thunder and added areas of
drizzle to the eastern plains. Also increased winds on the plains
Saturday afternoon with good mixing and strong pressure gradient
in place.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 220 PM MDT Fri May 20 2016

Current radar and satellite imagery showing increasing convection
over the foothills and northern portions of the CWA. The surface
low that was in place on the lee side of the mountains has
degraded bringing sfc flow more southerly over the eastern
portions of the CWA. A dry line is setting up along a line from
Weld county SE into Washington that will increase CAPE and
convection in that region for storms moving off the northern
foothills. Steering flow is SE so many storms may instead move into
WY vs east across our northern counties. Still maintain a chance
of thunderstorms in the mountains and foothills with a slight
chance on the plains. Further south mid level temperatures will
most likely be too warm for much convection so storms will most
likely produce some light rain and gusty winds.

For tonight the storms will wind down around 5 pm and storms will
end from west to east. Pressure falls ahead of an approaching
trough over CA will again turn winds on the plains more SE. This
will help to usher in increasing moisture west onto the plains.
Models are indicating a Denver cyclone setting up to the north of
the city that will help to pull moisture more west. At this time
will keep the city of Denver and DIA under patchy fog conditions
with heavier areas of fog further east and north. This low fog and
increased moisture will lift into a lowered stratus that will
delay initial warming...however with dry SW flow increasing
through the day conditions should still warm to lower 80s for much
of the plains. Convection is looking less probable with most areas
capped. Kept a slight chance of storms in the mountains with
decent lapse and CAPE values above 1000 j/kg at higher elevations
but have kept it mostly over the far eastern portions of the CWA
for late afternoon. Do not expect severe but light to moderate
rainshowers and gusty winds will be possible with the stronger
storms.

.LONG TERM...(Saturday night through Friday)
Issued at 220 PM MDT Fri May 20 2016

Drier air will move over the area Saturday night. There will just
be a slight chance for thunderstorms during the evening over the
northern mountains and far eastern plains.

Sunday will be warm ahead of a cold front that will push through
during the day. Highs are expected to be in the mid 70s to lower
80s across northeast Colorado. Moisture is somewhat limited
Sunday and will keep convection isolated. Best chance for storms
will be over the higher terrain and northeast corner of the
state. If enough moisture hangs on over the northeast corner
there could be a couple strong to severe thunderstorms.

It will be cooler Monday behind this system. There should be
enough moisture and instability for another round of isolated
showers and thunderstorms. Most of them will be found over the
higher terrain.

A weak southwest flow aloft will persist Tuesday through Friday
over Colorado. Mainly isolated afternoon/evening showers and
thunderstorms are expected. May be a better chance for storms
Thursday and Friday as an upper level trough moves into the
central Rockies. Temperatures will be at or slightly below normal
Tuesday through Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 728 PM MDT Fri May 20 2016

VFR conditions will prevail, although there is still a brief
window of fog potential from 12Z-15Z Saturday. Denver cyclone
will support stratus and fog development over the eastern plains,
wrapping it back toward the Front Range late tonight and early
Saturday morning. Main threat is still from KFNL and KGXY east to
KAKO, KLIC, and points east.  At KDEN and KBJC probability of fog
is only about 20% right now, but still something to watch closely
as any fog development would likely take the visibility down to
1/4SM. No threat of thunder for the Front Range airports and KDEN
through Saturday evening. Southerly winds near 15-20 knots with a
few gusts near 25 knots til 06z gradually weakening and becoming
variable by Saturday morning. Then expect them to increase again
and have bumped up KDEN and KAPA to near 20 knots with gusts 25-30
knots expected to develop by 20Z Saturday during peak heating and
mixing.

&&

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

$$

UPDATE...Barjenbruch
SHORT TERM...Bowen
LONG TERM...Meier
AVIATION...Barjenbruch



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