Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 211632
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1032 AM MDT Wed Jun 21 2017

.UPDATE...
Issued at 1032 AM MDT Wed Jun 21 2017

A very warm start to the day with KDEN reaching 90 degrees a
little before 10am. Highs on track to be in the mid 90s to lower
100s today. Adjusted high temperatures up a degree or two for this
afternoon. A decent chance at tying or breaking the record high
of 99 at KDEN. GOES 16 satellite water vapor imagery showing dry
air and subsidence over the area at this time. Moisture should
increase from the west later today and help produce another round
of high based showers and thunderstorms late this afternoon and
evening. Rainfall will light with the convection. Lightning and
gusty outflow winds will be the main threats.

&&

.SHORT TERM...(Today and tonight)
Issued at 339 AM MDT Wed Jun 21 2017

Only minor changes from yesterday. At first, we expected more
moisture today, but it looks like WNW flow aloft will actually be
bringing in drier air behind a weak shortwave this morning. The
end result will likely be a similar day. Guidance has mid to upper
90s with the NAM MOS pegging DIA at 100. Record for Denver today
is 99, and it should be close. Expect any convection to be weak
and late in the day. We could wind up with decent coverage of
weak convection in the evening again, but with the low/mid level
drying from the northwest, this would likely favor the central
mountains and Palmer Divide areas. With a little more northwest
wind aloft, there will be a bit more of a breeze at the surface
today. This will bump the fire danger up another quarter step, but
we are still marginal at most for fire weather highlights, as the
fuels continue to dry. Areas with highest fire danger are
Gilpin/Clear Creek/Park counties.

.LONG TERM...(Thursday through Tuesday)
Issued at 339 AM MDT Wed Jun 21 2017

On Thursday, the ridge over the desert southwest shifts southward
as a short wave trough moves into the the Dakotas in the
afternoon. A weak cold front associated with this passing system
will push into the northeast plains in the afternoon. The models
still show good boundary layer CAPES in the afternoon, around 1500
j/kg along and south of the frontal boundary. It will not be as
hot but still close to 90 prior to fropa. Precipitable water
values will be close to an inch as well with good directional
shear in the NAM12 forecast soundings. As a result, could see some
of those storm produce large hail and damaging winds but could
not rule out a brief tornado. On Friday, a stronger surge of cool
air spreads across the northeast plains. The best chc of
thunderstorms on Friday will be over the elevated terrain to the
west and south of Denver. Much cooler on Friday with a stronger
inversion present around 675 mb. As a result, vertical extent of
the cells will be severely hampered so could see more showers vs
tstms over the plains. Saturday, systems passing to the north
continue to bring cold frontal surges into northeast Colorado.
Best chc of showers/tstms at that time may be south of Interstate
70, over the Palmer Divide and southern Front Range Foothills.
The stable airmass remains in place on Sunday as well with little
temperature recovery. Best chc of thunderstorms on Sunday should
again be over the higher terrain.  The trend will start to shift
by Tuesday of next week with the ridge progged to rebuild over the
west. Drier and warmer, with a west/southwesterly flow aloft with
primarily just isolated thunderstorms coverage in the aftn and
evening.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1032 AM MDT Wed Jun 21 2017

No aviation issues expected through Thursday. Outflow winds from
showers and thunderstorms may produce a wind shift or two at the
Denver airports 21Z through 04Z. Otherwise, light normal diurnal
winds are expected.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

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



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