Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 252102
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
302 PM MDT WED MAY 25 2016

.SHORT TERM...(This afternoon through Thursday)
Issued at 302 PM MDT Wed May 25 2016

An upper low over southern California this afternoon will move
into northern Arizona tonight then into southern Colorado
tomorrow. A surface low has formed over southeastern Colorado with
easterly flow into the forecast area bringing in low level
moisture. Drier air streams in aloft with with dewpoints in the
single digits to teens in the mountains with gusty westerly winds.
A few boundaries over northern and eastern plains are helping to
fire convection this afternoon. CAPE values of 500 J/kg near the
urban corridor to 1500 J/kg near the Kansas border this afternoon
will allow for some stronger storms with small hail and gusty
outflow winds to form...however no severe strength storms are
expected. There may be a small chance near the Nebraska border.
Left over moisture will likely produce patchy fog and low clouds
out near the Kansas border...affecting areas near Julesburg down
to Akron and possibly down to Limon.

The upper low will move closer tonight bringing upward QG lift
while surface winds begin to turn northeasterly upslope as the
surface low pushes southeast. Will look for moisture to increase
and some showers possibly forming over the upslope favored areas
by early Thursday morning. Enough CAPE will still hang around for
a chance of a thunderstorm over the plains as well. The surface
low will be reforming and deepening over southeastern Colorado
Thursday afternoon as the upper low moves into southwestern
Colorado. CAPE values are expected to increase to 750 J/kg near
the urban corridor to near 3000 J/kg out over Washington and
Lincoln counties with 0-6km shear in the 35 to 50 kt range. This
will likely support the development of severe strength storms with
large hail and strong winds being the greatest threats. QPF values
will be increasing with the upslope flow...models have up to half
an inch of rain occurring by evening...with thunderstorms able to
put down localized areas of greater amounts.

.LONG TERM...(Thursday night through Tuesday)
Issued at 302 PM MDT Wed May 25 2016

By 00z Friday a broad upper low will be over southern and central
Colorado. A well defined boundary is forecasted by various models
to lie from a surface low over SE colorado into portions of
western Kansas. To the North of this boundary NNE winds with
increasing RH will interact with SSW drier winds from the south
to create a significant dryline. NAM and GFS showing intrusion of
mid level cold air with the low as it progresses into SE colorado
increasing lapse rates. Model soundings for 00z Friday show a
strong potential for severe hail with CAPE values of 1000 j/kg or
more and deep shear values in the 40s. In addition...NAM
soundings are still indicating some CIN but with high low level
shear...especially over portions of southern Lincoln county where
the boundary is currently forecasted to set up I can not rule out
a possible tornado at this time.

In the mountains strong easterly upslope flow combined with high
levels of moisture and wet bulb zero levels dropping close to
10,000 ft will result in increasing chances of accumulating snow
thursday night into Friday morning. 24 hour accumulations ending
by 12z Friday morning are showing 4 to 20 inches for the higher
elevations of the Front Range mountains and Mosquito Range. I will
hold off on an advisory for now but upcoming model runs will need
to be monitored for consistency. The western plains will have a
slight chance of showers and thunderstorms by the afternoon with a
higher chance south to the Palmer Divide. The surface low will
continue to move eastward through the day Friday bringing the
boundary further south in Kansas. By 12z Friday there is
increasing QG descent and subsidence as the upper level ridge
moves into western CO. This will help to end convection across the
region with a slight chance of rain continuing into the early
evening. Highs on Friday will be cooler with temperatures only
getting into the mid 60s on the plains.

Friday night and through the weekend ridging will move over the
state with decreasing precipitation chances on Saturday.
Temperatures will rebound with highs closer to seasonal normals in
the mid 70s through Tuesday. On Sunday...zonal flow into a weak
trough will push in increasing moisture into the high country
bringing another round of showers and afternoon thunderstorms
Sunday and Monday. The plains will see a slight chance of
thunderstorms by Monday that will continue into Tuesday as the
upper level low continues to spin over southern CA.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 302 PM MDT Wed May 25 2016

Storms are expected to stay north and east of the Denver area this
afternoon and evening. Easterly winds over the Denver area are
expected to trend to the northeast this evening...then likely
going to drainage briefly overnight. A surface low will deepen
over southeastern Colorado to increase northeasterly winds
Thursday morning and into the afternoon. Increasing moisture will
produce showers near the foothills and Palmer Divide tomorrow
morning then increase across the area in the afternoon with
thunderstorms likely. Visibility and ceilings will stay VFR
through Thursday afternoon...with a slight chance of ceilings
lowering to 4500 feet with storms.

&&

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

$$

SHORT TERM...Kriederman
LONG TERM...Bowen
AVIATION...Kriederman



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