Special Weather Statement, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
252 PM MDT Sun Aug 2 2020

.SHORT TERM...(This evening through Monday)
Issued at 235 PM MDT Sun Aug 2 2020

Forecast still on track with strong storms developing over the
foothills. Low level moisture hanging on with dew points in the
lower to mid 50s north of Denver. This air mass is still weakly
capped, but the northerly component to the flow aloft is keeping
most of the clouds over the mountains. We're still on track to
have enough CAPE for large hail. The one complication is not a
surprise. The HRRR is now trending toward more foothills
convection pushing an outflow boundary eastward in the mid to late
afternoon hours, before a storm drops southward out of Wyoming.
This is probably right. Depending on how fast it comes eastward,
it may be a little earlier than optimal for severe storms against
the foothills. This might push the greatest risk a little further
east--along or a little east of I-25. Another thing pointing to
this is that the easterly flow isn't that strong in the I-25
corridor, it gets better further east. But the current storm over
the foothills is already pretty strong, so there is some severe
risk across the watch area. Main threat still looks to be hail
with moderate CAPE and shear. We're seeing some heavy rain, but
the storms should move fast enough to limit the flood threat to
minor street flooding.

This afternoon's convection should progress southeastward this
evening and be out of the area by about midnight. Monday looks
much like today, though a little warmer and drier so the storm
intensity might be more marginal again with a bit less of a hail
threat and a little more wind threat. Forecast highs are 3-5
degrees warmer and a little above guidance, which looks good.

.LONG TERM...(Monday night through Sunday)
Issued at 235 PM MDT Sun Aug 2 2020

On Tuesday, a persistent pattern will continue with an upper
level over the Desert Southwest with a northwesterly flow aloft
over eastern CO. ML CAPES still high with values 2100-2500 j/kg,
and precipitable water values at or above 1 inch. SPC keeps
eastern CO under a marginal risk of severe thunderstorms for
Tuesday. Large hail and damaging wind gusts the main threat. A
weak short wave is progged to pass to the north and east of CO
around 00z Wednesday with a weak front pushing into the northeast
plains. Temperatures on Wednesday will be a couple of degrees
cooler. The synoptic pattern remains similar as well. The airmass
over the northeast plains may be more stable with a slightly
cooler airmass in place. Focus at that time may shift more to the
Palmer Divide area. Thursday into Friday, a long wave trough move
onto the west coast, with the ridge axis getting pushed eastward
over the Southern Great Plains. The flow aloft over CO will
transition to southwesterly, with weak embedded short wave,
possibly moving southwest to northeast across the state late
Thursday into Thursday night. Friday through Sunday, the ridge
will be centered over Texas. Moisture around the ridge at that
point may shift more to eastern and southern CO, with a drier
airmass over the mountains. This will result in warmer
temperatures and less thunderstorm coverage in the afternoon
and evening.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 235 PM MDT Sun Aug 2 2020

VFR will prevail through Monday. Scattered thunderstorms in the
Denver area through 02z that could produce localized MVFR
visibilities. A severe storm with large hail and wind gusts to 50
knots is possible. More likely storms will produce brief heavy
rain, small hail, and a couple of wind shifts with 30 knot gusts.
Scattered strong storms are expected again late Monday afternoon
with similar threats.

&&

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

SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Gimmestad

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1104 AM MDT Sun Aug 2 2020

COZ030>051-031715-
Jackson County Below 9000 Feet-
West Jackson and West Grand Counties Above 9000 Feet-
Grand and Summit Counties Below 9000 Feet-
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Central and Southeast Park County-
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Northeast Weld County-Central and South Weld County-Morgan County-
Central and East Adams and Arapahoe Counties-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County-
Southeast Elbert County Below 6000 Feet/South Lincoln County-
Logan County-Washington County-Sedgwick County-Phillips County-
1104 AM MDT Sun Aug 2 2020

...SEVERE THUNDERSTORMS POSSIBLE THIS AFTERNOON...

This hazardous weather outlook is for northeast and north central
Colorado.

.DAY ONE...Today and Tonight

Scattered thunderstorms will develop this afternoon over the
Front Range mountains and the I-25 corridor. The storms will
toward the southeast and will be mainly south of Denver by mid
evening. A few severe storms are possible with hail up to golf
ball size and wind gusts to 60 mph, along with heavy rainfall and
minor flooding. The severe storm threat will mainly be over and
near the foothills, west of a line from Cheyenne to Limon
including the Denver metro area, from 3 PM to 7 PM. In other
areas, thunderstorms will be weaker and less numerous but could
still produce small hail and brief heavy rain.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

There will be a good chance of showers and thunderstorms Monday
through Wednesday mainly in the afternoon and evening hours. A few
storms over the plains may be severe Monday and Tuesday. Large
hail and damaging winds will be the main threats.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed after 1 PM.

Gimmestad/Cooper

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