Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 271641
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1041 AM MDT FRI MAY 27 2016

.UPDATE...
Issued at 1041 AM MDT Fri May 27 2016

The band of rain across the eastern plains is decreasing in area
as well as intensity late this morning. The band is slowly moving
west but is expected to continue to weaken. Rainfall rates will
likely be below a tenth of an inch an hour below the band, and
will continue to lessen. As the day`s heating continues, am still
expecting a few thunderstorms to be able to develop this afternoon
across the forecast area. However with weak CAPE but a cooler
airmass, could still see small hail falling out from them.

Downward QG vertical velocities along with drying downsloping
pattern will diminish showers and thunderstorms this evening, with
only a slight chance of them remaining in NW flow over the
mountains. There is still thunderstorms in the forecast this
evening, however conditions don`t look very favorable, may strip
these out later.

&&

.SHORT TERM...(Today and tonight)
Issued at 350 AM MDT Fri May 27 2016

The upper level low will track across southeast Colorado and into
western Kansas today. A deformation band has developed on the back
side of the low. This area of rain should shift east with the low
this morning. Lowered pops for the northern half of the Front
Range. Will keep the higher pops south and across the eastern
plains due to the area of rain. Rainfall will be light to moderate
with additional amounts mostly less than a half inch. Most of the
precipitation has remained east of the mountains and is expected
to stay east, so will cancel the Winter Weather Advisory.

Airmass becomes slightly unstable this afternoon, mainly over the
higher terrain and far northeast corner of the state. Will have
scattered showers and thunderstorms in the forecast for this with
higher pops over the eastern plains where the deformation zone is
expected to be.

Rain showers and thunderstorms are expected to decrease late this
afternoon and evening as the airmass stabilizes and the low moves
east of the state. Will have low pops in the for the evening and
then end them most locations after midnight. There may be a few
stray showers over the mountains and far northeast Colorado after
midnight and will keep slight pops in the forecast.

.LONG TERM...(Saturday through Thursday)
Issued at 350 AM MDT Fri May 27 2016

The Memorial Day weekend should start out dry Saturday morning
with a weak mid-level shortwave ridge over the area and a light
west-northwesterly flow spreading drier and warmer air over the
fcst area. by afternoon some of the models show this ridge nosing
up into the Dakotas and a weak shortwave trough on its heels
passing over the CWA during the late afternoon/early evening
hours. Strong solar heating resulting in steep lapse rates and the
lingering presence of low-level moisture should manage to produce
isolated to scattered showers/t-storms over the Front Range mtns
and higher foothills by early afternoon. Destabilization aloft and
additional heating of the boundary layer may be sufficient to
spark a few late afternoon/evening t-storms on the plains and
Palmer Divide. Potential instability and shear do not appear
adequate to produce strong/deep convective updrafts leading to
severe t-storms. Furthermore qpf guidance indicates the bulk of
the precip that day will fall over higher elevations...and most of
that less than a quarter inch. As for Temperatures on
Saturday...model guidance indicates a 10-12deg f warmup for most
areas. That seems reasonable with the warming aloft and with a few
more hours sunshine.

Sunday may begin about the same with morning sunshine and mild
temperatures. however by mid to late morning a tight lee slope
pressure gradient creates gusty south-southeasterly sfc winds on
the plains according to the NAM...GFS and Canadian models which
then drives increasing amounts of low-level moisture up into
east-central and northeast Colorado. Could see isolated to widely
scattered t-storms forming on the plains by mid-afternoon...but
the stronger convection will probably stay east of the CWA as it
now appears. Meanwhile mountain areas should again see another
round of afternoon and early evening showers/t-storms but probably
with the coverage expected on Saturday since there does not appear
to be any forcing mechanism aloft. Sunday temperatures should
continue to rise by another 3-5 deg f for most locales with mid-to-
upper 70s on the plains.

For Memorial day...models are offering mixed signals. The NAM
shows another shortwave trough swinging over the area during the
day and interacting with a moisture rich sely low-level flow
together with bndry layer cyclongensis across the northeast
corner of the state. This would potentially result in a stormy
afternoon and evening for this area. Whereas...the GFS...ECMWF
and Canadian models indicate a drier day for the CWA with a warm
and dry swly flow aloft. I like a blend of the models here since
I`m not sure the boundary layer will dry out as much as the models
indicate as they all generally indicate sely sfc winds on the
plains. Temperatures on Monday about the same or perhaps a deg or
two lower than the day before.

For the period Tuesday-Thursday...models continue to indicate
troughing over the Rocky Mtn Region and as a result a slight dip
in temperatures and a slightly better chance of afternoon and
evening showers/t-storms. The best chance for this activity
appears to be on Tuesday and Wednesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1041 AM MDT Fri May 27 2016

Rain band has backed west slightly at the same time diminishing. Ceilings
are expected to range from 3000 to 6000 feet through 22z, then
start improving through the rest of the afternoon and clear out
this evening. There will be a slight chance for weak
thunderstorms after 18z, but they`ll be very isolated, so will not
include in the TAFs at this time. Gusty north to northeasterly
winds with gusts to 25 knots possible will decrease after 00z and
eventually back toward drainage. Light winds are expected through
18z Saturday.

&&

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

$$

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



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