Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 061033
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
433 AM MDT Thu May 6 2021

.SHORT TERM...(Today and tonight)
Issued at 433 AM MDT Thu May 6 2021

Dry and subsident northwest flow aloft will be across the forecast
area today. We`ll start our advertised warmup with mostly sunny
skies and downslope flow. This should push high temperatures into
the lower 70s across most of the plains, with 60s in the
foothills and mountain valleys, and upper 40s and 50s over the
mountains. There was some patchy stratus across the plains early
this morning, but this will dissipate with the drier northwest
flow developing.

Mostly clear skies will persist through tonight as the ridge axis
moves across the state. Low temperatures will be a few degrees
above normal as warm advection continues.

.LONG TERM...(Friday through Wednesday)
Issued at 433 AM MDT Thu May 6 2021

Friday, Colorado will be under the axis of the ridge and the
warmest conditions of the period. Models are still showing those
700 mb temperatures greater than 10 C across most of northeast
Colorado, which imply highs in 80s F on the plains and 70s F in
the mountain valleys. There will be strong mid level instability
with steep lapse rates over 9 C/km in many areas, and there should
be enough mid level moisture on the back end of the ridge to
support the development of isolated thunderstorms over the higher
terrain during the afternoon. These storms will move over the
plains in the evening but the lower levels will be dry, so expect
mostly virga and gusty outflow winds from high-based storms. Over
the plains, there are swaths of high DCAPE to around 1000 J/kg in
the afternoon.

Saturday, moisture and lift will increase ahead of a trough
advancing from the Pacific Northwest to the Great Basin. A front
will also push through the plains in the late day or early
afternoon, bringing increase in low level moisture and cooler air.
Highs should fall to the upper 60s F and lower 70s F on the
plains and upper 50s F and lower 60s F in the high country, and
snow levels will begin to fall again as well. Expect scattered
thunderstorms and showers, with snow in the mountains.

Sunday, models show the trough starts to stall as it advances to
the northern Rocky Mountains, then heights fall to our west over
Nevada and Utah, and another cold front with some shallow upslope
flow pushes into the Front Range. Moisture will continue to
increase and precipitation will become more widespread and
intense. Upslope flow will favor the foothills and adjacent
plains, where there is still a wide range of QPF but generally
around 1 to 1.5 inches currently seems likely based on ensembles.

There is still low model consensus about the synoptic situation
early next week, but continue to show good moisture and lift, with
colder air and widespread precipitation. The ECM and GDPS are
slightly more progressive with the system than the GFS, but all
have the trough exiting by late Wednesday or early Thursday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 433 AM MDT Thu May 6 2021

VFR conditions will persist through Friday. We expect the patchy
stratus to stay north of KDEN this morning and dissipate. Very
low chance that patchy fog would develop now til 14Z due to the
light and variable winds and narrowing of T/Td spreads. Winds will
become more easterly by 18Z, and then expect a slow transition
back to 10 kt drainage winds tonight 03Z-07Z.

&&

.HYDROLOGY...
Issued at 433 AM MDT Thu May 6 2021

No precipitation will occur today or tonight.

Friday will see a slight chance of showers and storms that will
be high based and provide mainly gusty winds with very little
rainfall. Saturday will see isolated to scattered showers and
storms through the afternoon and evening, with generally light
rainfall and low flood potential.

Precipitation coverage and intensity will increase by Sunday
afternoon and continue into Monday. There is still uncertainty on
amounts with a colder airmass bringing snow levels down into
Monday helping to lower the potential impact slightly.

&&

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

$$

SHORT TERM...Barjenbruch
LONG TERM...Direnzo
AVIATION...Barjenbruch
HYDROLOGY...Direnzo


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