Severe Thunderstorm Warning 334, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
543 PM MDT Fri Jul 21 2023

.SHORT TERM...(This afternoon through Saturday)
Issued at 1028 AM MDT Fri Jul 21 2023

A much quieter afternoon across Colorado versus yesterday given a
drier and subsident northwest flow pattern. Latest radar showing
an isolated shower/storm trying to brew across Jackson county and
isolated thunderstorms further north across Wyoming. There is
still enough moisture and marginal instability for isolated
thunderstorms over mountains and higher terrain, especially over
the CYS ridge. Latest HRRR and recent runs insistent on a storm
forming just over the border and into northern Weld and Morgan
counties through this evening. Will have isolated pops through
this evening for mountains and adjacent plains. The far northeast
plains look to be too capped for any storms. Any storms that do
form will diminish quickly by late evening with loss of solar
heating and subsident airmass.

Saturday looks to be similar to today with mainly dry conditions and
warming temperatures. High pressure ridge aloft remains west of
Colorado and continues to build across the Great Basin. Thermal
ridge building from the west with 700mb temperatures rising another
2-4 degrees C. This will support high temperatures around 90
degrees on the plains. The convective outlook is pretty sparse
with mayhap a few weak showers/storms over the mountains and
higher terrain.

.LONG TERM...(Saturday night through Thursday)
Issued at 230 PM MDT Fri Jul 21 2023

Key message: Summer heat is here for a lengthy stay.

A ridge of high pressure will dominate the region for the next
several days to come. The upper level high will shift slowly
eastward over the Southern Rockies through the weekend, while a
rather high amplitude ridge will extend northward from that
across Colorado and into the Northern Rockies/High Plains. This
pattern will bring a return of hot temperatures to the forecast
area, with highs pushing into the mid to upper 90s and possibly a
couple 100F degree readings across the plains and I-25 Corridor
for Sunday and Monday. The airmass will remain relatively dry,
although expect a few high based showers and storms late Monday as
moisture slowly builds under the ridge.

By Tuesday and Wednesday, a shortwave will move across the
Canadian/US border, flattening the ridge just a bit. That should
also drag mid level moisture across the forecast area increasing
the chance of showers and storms. We don't see any big monsoonal
push with this, but just enough for a little higher coverage of
precipitation. Most storms will likely only produce light rain
with gusty winds considering lack of low level moisture and
inverted-v profiles. Temperatures will remain above normal with
mostly lower to mid 90s over the plains and I-25 Corridor, just a
couple degrees cooler thanks to increasing moisture and a few
late day storms around.

Thursday could have a chance of a little more cooling with
potential for a backdoor cool front. At the same time, we could be
looking at increasing fire weather potential for the high country
as westerly flow increases in the wake of the passing shortwave.

For Friday and probably through next weekend, we're shaping up for
more heat as prognostications show a 600dm high building over the
Four Corners area.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 541 PM MDT Fri Jul 21 2023

At this time don't expect isold tstms to the NW and North to
affect DIA.  Otherwise look for winds to become more southeast
in the next few hours and then go to drainage by 06z.

&&

.HYDROLOGY...
Issued at 230 PM MDT Fri Jul 21 2023

The hi-res models generate the best thunderstorm coverage over
Larimer County today, so the flash flood risk for Cameron Peak
will be limited, with minimal risk elsewhere. Only isolated
showers are expected on Saturday afternoon over the burn scars
with little or no chance of flash flooding.

Drier conditions expected, although a few storms will develop
toward Monday through the middle of next week. For the most part
these storms will be weak and only produce light rain, and little
or no threat of flash flooding even in the burn scars.

&&

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

SHORT TERM...Entrekin
LONG TERM...Barjenbruch
AVIATION...RPK
HYDROLOGY...Entrekin/Barjenbruch

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
938 AM MDT Fri Jul 21 2023

COZ030>051-221545-
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-
938 AM MDT Fri Jul 21 2023

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

.DAY ONE...Today and Tonight

Thunderstorm activity will decrease considerably today with only
isolated to scattered thunderstorms, mainly over the mountains and
higher terrain over the Cheyenne ridge and Palmer Divide. One or
two storms could briefly produce hail up to one inch and/or wind
gusts to 60 mph. The airmass over the far northeast plains will
likely be too stable for any thunderstorm development.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Temperatures heat back up this weekend and next week. For Sunday
and Monday, highs are expected to reach the mid to upper 90s
across northeast Colorado. Chances for thunderstorms will be low
through Monday. Moisture increases across the area Tuesday. This
will bring a better chance for showers and thunderstorms beginning
Tuesday and continuing through at least Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today and tonight.

Special Weather Statement
National Weather Service Denver CO
542 PM MDT Fri Jul 21 2023

COZ038-039-043-220015-
Central and South Weld County CO-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County
CO-Larimer County Below 6000 Feet/Northwest Weld County CO-
542 PM MDT Fri Jul 21 2023

...A strong thunderstorm will impact portions of southwestern Weld
and southeastern Larimer Counties through 615 PM MDT...

At 542 PM MDT, Doppler radar was tracking a strong thunderstorm 4
miles northwest of Berthoud, or 15 miles south of Fort Collins,
moving southeast at 30 mph. A second storm was located just east of
Berthoud, also moving southeast.

HAZARD...Winds in excess of 30 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Southwestern Loveland, Firestone, Johnstown, Frederick, Milliken,
Berthoud, Mead, Platteville, Gilcrest and Carter Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4032 10524 4040 10519 4032 10471 4008 10488
TIME...MOT...LOC 2342Z 295DEG 27KT 4034 10511

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH

HIRIS

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