Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 030154
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
754 PM MDT Tue Jun 2 2020

.UPDATE...
Issued at 750 PM MDT Tue Jun 2 2020

Only isolated showers and storms were over the nern plains early
this evening. Satellite shows a disturbance over sern Wyoming
moving eastward with strong storms associated with it. Appears
this activity will stay over wrn Nebraska and not affect the far
nern plains overnight.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 310 PM MDT Tue Jun 2 2020

A few showers and storms are beginning to form but have gotten a
late start due to cloud cover for much of the day. Because of the
cloudiness, the coverage of these showers and storms should remain
limited through the rest of the afternoon and evening.
Nonetheless, slight chance PoPs were kept through 10-11pm because
there will be increasing moisture and upslope flow especially near
the Cheyenne Ridge which could keep storms going. The rest of the
night will be dry and mild as low temperatures will be 5 to 10
degrees above normal.

West-northwesterly mid to upper level flow will increase across
far northern Colorado on Wednesday with 500 mb winds reaching
near 50 knots by the afternoon. Temperatures will once again be
hot with highs reaching the upper 80s to low 90s across the urban
corridor and plains. A dryline will setup across the eastern
plains by the afternoon roughly along a line from Sterling to
Limon. This boundary may provide enough low level convergence to
generate a few strong to severe storms especially across the
northeast corner of the state. With mixed layer CAPEs as high as
2,500 j/kg and deep layer wind shear around 40 knots, any storms
that develop over Logan, Washington, Sedgwick, and Phillips
Counties will be capable of producing large hail up to the size of golf
balls and damaging wind gusts up to 60 mph. Further west,
isolated non-severe thunderstorms will develop and won`t produce
much rainfall but could produce a few wind gusts up to 40 mph.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 310 PM MDT Tue Jun 2 2020

A few storms may still be ongoing over the far eastern plains
Wednesday evening, mainly south and east of I-76, with a few
showers possible in the mountains. Clouds will remain over the
forecast area, helping to keep low temperatures above normal
still.

On Thursday, the upper ridge will move ever so slightly east,
allowing for slightly warmer temperatures and a drier environment.
There won`t even be easterly winds into the plains, so overall,
any convection should be high based with strong outflow winds the
bigger threat of storm hazards. Higher CAPE values are expected
over the far northeast corner of the state, so may see a stronger
or possibly severe storm out that way. A ripple in the westerly
flow aloft is expected to push across northern Colorado in the
evening and overnight, so increased PoPs overnight for this.

On Friday, the flow aloft will turn south-southwesterly as a low
off the southern California coasts quickly lifts northeast into
the Great Basin. High pressure sliding down the Great Plains will
once again push in southeasterly winds carrying in more low level
moisture. This combined with the warmer temperatures being
advected in from the more southerly flow will increase theta-e
values across the plains. Subtropical moisture will also move in
from the southerly flow aloft which will increase showers and
storms across the entire forecast area. Timing of this moisture
however is different between the three longer range models. If the
faster GFS is correct, storms will increase Friday evening and
overnight. Stronger winds aloft will increase shear, so Friday
will have the potential for strong to severe storms. If it`s later
like the EC or even later like the Canadian, will have to wait for
Saturday.

The upper low will be opening to a trough and moving from the
Great Basin northeast across the Northern Rockies and into Montana
Saturday, though there are timing differences between the models.
GFS remains the fastest, with the EC the middle ground and the CMC
being the slowest. This will move the jet across Colorado sometime
on Saturday, with a surface low deepening along the lee of the
Rockies to increase southerly winds across the plains. The
increase in winds along with dry warm air will increase fire
weather concerns over the areas with dry fuels.

Sunday will be even more of a concern as the southwesterly flow
stays over the area with strong speeds, hot temperatures and dry
conditions. Widespread critical fire weather conditions will
likely spread across most of the forecast area. Will be in
constant touch with land managers for fuels updates.

The upper trough over the Pacific Northwest will then move east to
finally bring the next chance for a cool down and more
precipitation Monday and Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 740 PM MDT Tue Jun 2 2020

Main concern, for late tonight, would be the potential for
stratus to affect DIA, in the 12z-15z time frame, as a Denver
cyclone develops. The stratus should burn off rather quickly if it
does form. Otherwise easterly winds this evening will become more
southeast to south by 06z and then become more variable in
direction by 12z due to location of Denver cyclone.

&&

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

$$

UPDATE...RPK
SHORT TERM...Danielson
LONG TERM...Kriederman
AVIATION...RPK


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