Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 190214

Area Forecast Discussion
National Weather Service Denver/Boulder CO
814 PM MDT Wed May 18 2022

Issued at 804 PM MDT Wed May 18 2022

Entire area is now shower/thunder free as remaining showers across
the Palmer Divide have ended. Skies are mostly clear across
Northern Colorado this evening but there will be some increase in
high clouds overnight given clouds already working into northwest
Colorado. The clouds over far eastern Colorado will gradually
dissipate from earlier thunderstorms.

UPDATE Issued at 556 PM MDT Wed May 18 2022

Have just cancelled remainder of the severe thunderstorm watch
across Lincoln county for the evening. Still some scattered
showers over southeast Lincoln county and those will be ending by
8 pm as the severe weather threat is over. Elsewhere, expect
mostly clear skies and gradual clearing across the Palmer Divide
by later this evening.


.SHORT TERM...(This evening through Thursday)
Issued at 253 PM MDT Wed May 18 2022

Thunderstorms will continue through this evening pushing eastward
towards the Colorado/Kansas border mainly across the Palmer Divide
and nearby eastern plains. These storms will produce small hail and
wind gusts up to 35-45 mph; there has been reports of pea size hail
so far. With PWATS near 0.50 from the sounding this morning and
current dew points in the mid 30s to lower 40s, not expecting much
rainfall accumulation from these storms. Tonight, zonal flow will
end and an upper level trough will push into our region where
pressure gradients increase the early morning hours on Thursday.
Additionally, strong downslope westerly winds will occur by late
Thursday morning into afternoon. This pattern, along with widespread
dry conditions of low relative humidity levels near 10-12
percent, will bring critical fire weather conditions mainly for
the entire Front Range including South Park through Thursday

.LONG TERM...(Thursday night through Wednesday)
Issued at 253 PM MDT Wed May 18 2022

...Winter storm to impact the region starting early Friday and
continuing through Saturday...

...Wet and unsettled pattern extends into mid week with increased
precipitation chances...

A closed upper low will be over the US/Canada border Thursday night
with a trailing trough extending across the northern Rockies. This
will leave Colorado in predominately zonal flow with a lee surface
low over the eastern plains. The low will shift east and a strong
cold front will drop south Thursday night increasing moisture and
advecting cooler temperatures helping to bring critical fire weather
conditions to an end. The upper trough will continue to drop south
with a jet max pushing into northwestern Colorado during the
afternoon on Friday. Ahead of the trough increasing moisture will
form over the northern mountains with a gradual increase in mid-
level moisture over the lower elevations. There is expected to be
enough instability with increasing QG along with moderate NW flow to
produce snow over the Park and Gore ranges as early as 3-4 am Friday
morning. Increasing northeast flow at the surface in the post-
frontal airmass will help to create an upslope effect for the
foothills that should get precipitation going Friday morning. As the
trough drops south so will the moisture and better instability with
model soundings showing a saturated and snow producing profile by
the afternoon on Friday. This will be aided by the aforementioned
instability as well as the enhanced northeast upslope through 700
mb. At this point it appears that precipitation will start out as
rain for the lower elevations with snow likely above 6500ft. The
snow level will drop into the evening on Friday with rain changing
over to snow for the Urban Corridor and Metro area by midnight. With
the warm temperatures beforehand combined with the higher sun angle
given it`s May and not December the snow to liquid water ratio will
be quite low with a great deal of initial melting expected.

Latest ensembles are zeroing in on lows around freezing for Friday
night into Saturday for the metro area with temperatures expected to
stay in the 30s through the day. Precipitation will be in the form
of snow and will continue overnight and through the afternoon on
Saturday. The synoptic pattern for the weekend has the trough
elongating and turning zonal across the state with the jet max and
is not expected to lift north until Sunday. Both the GFS and EC have
prolonged upslope components at the surface that will keep snow
going into Saturday afternoon for the metro area and eastern plains
and into Saturday evening for the southern foothills and Palmer
Divide areas. The snow will end north to south starting early Sunday
with snow ending currently expected by Sunday afternoon.
Temperatures Saturday into Sunday will drop below freezing with
ensembles showing possible 20s for the metro. The biggest things to
note with this storm are the impacts it will have to flowering
plants and trees. The weight of the wet snow could cause branches to
break and power interruptions or outages. For this reason we have
expanded the Winter Storm Watch to include the high mountain
valleys, foothills and the Urban Corridor starting Friday afternoon
and going through Saturday afternoon. These times could be updated
as the system timing continues to evolve.

For Sunday night into Monday a shortwave will pass over Colorado
bringing another round of rain and snow mainly to the Central
mountains and southern foothills then pushing onto the plains with
the right entrance region of the upper jet max into the morning
hours. There continues to be good upslope over the lower elevations
with surface winds from the north to northeast that will help keep
precipitation going into the overnight hours on Monday.

Wednesday is where the models begin to diverge with the GFS keeping
a train of shortwaves moving in NW flow with no signal for the EC.
Will maintain a model consensus for this time period with highs
gradually recovering into the 70s and low 80s by mid-week.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 804 PM MDT Wed May 18 2022

VFR through period with some increase in high level cloudiness
after 06z. Surface winds have shifted southeast across the
terminals and expect a further shift to south and southwest before
midnight. Main impact on Thursday will be increasing gusty
westerly winds after 17z with gusts up to 30kt possible. Strong
cold front expected to push through Thursday evening between
04-06z with increasing northeast winds.


Issued at 253 PM MDT Wed May 18 2022

Critical fire weather conditions will occur late Thursday morning
through Thursday evening. Widespread 10-12 percent low relative
humidity levels will impact parts of South Park, foothills,
Palmer Divide, urban corridor, and eastern plains Thursday
afternoon before a cold front moves through. Expect strong
westerly winds producing 30-40 mph wind gusts through Thursday
evening. Relative humidity will recover to 40-55 percent across
the region as a cold front moves through Thursday night.


Issued at 253 PM MDT Wed May 18 2022

A snow storm will be moving into the region Friday morning with
increasing precipitation along the foothills by Friday afternoon
and continuing through the day Saturday. Snow levels will drop to
6500 ft by Friday night with the possibility of 0.02-0.10 inches
in a hour. There is currently not a flash flood threat for the
burn scar areas.


Red Flag Warning from 11 AM to 8 PM MDT Thursday for COZ214-216-

Winter Storm Watch from late Thursday night through Saturday
morning for COZ031-033-035.

Winter Storm Watch from Friday afternoon through Saturday
morning for COZ030-032-034-036>041.



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