Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 270539

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1139 PM MDT Mon Jul 26 2021

Issued at 754 PM MDT Mon Jul 26 2021

Only minor changes needed to current forecast. Satellite does show
some increase in smoke so expect hazy skies to continue.


.SHORT TERM...(This evening through Tuesday)
Issued at 252 PM MDT Mon Jul 26 2021

Temperatures have been warming under mostly clear skies as the
ridge began to build today, up to around 94 F at Denver so far. I
adjusted temperatures up a bit to match but otherwise the forecast
trend is good. Convection has been very limited this afternoon,
only over the high terrain and producing little to no
precipitation or hazards so far. That 500 mb noted in the morning
sounding and mentioned in discussions this week appears to be
suppressing development as expected. Continue to expect some
isolated convection but confidence in any impacts is low. Models
have continued to back off considerably on convection and I
concur, and continued to reduce PoP. Our highest PoP remains over
Park and Summit Counties due to the better moisture in the
southwest part of Colorado.

It will be mostly clear overnight, with lows similar to or a few
degrees warmer than last night for most areas. Temperatures will
trend a bit warmer still tomorrow under mostly clear skies again
and rising heights. Expect the mid to upper 90s across most of the
plains, mid to upper 80s in the foothills and mountains valleys,
and 70s to low 80s in the mountains. Convection will probably be
even more limited tomorrow than it has been today.

.LONG TERM...(Tuesday night through Monday)
Issued at 252 PM MDT Mon Jul 26 2021

The upper level ridge continues to dominate the synoptic picture
Wednesday with PW values around half an inch across the higher
elevations and up to 0.8 for most of the far eastern plains
counties. According to model soundings there is a substantial dry
intrusion in the mid-levels with a slightly cooler surface flow from
the southeast that will help to keep conditions mostly dry. There is
a small chance of weak moisture helping to kick off isolated
convection over the higher foothills so will keep a mention of low
pops in the forecast for Wednesday late afternoon. Otherwise 700mb
temperatures in the 18-19C range will help to bring highs back into
the upper 90s.

For the latter half of the week the upper level ridge will shift
eastward and elongate helping to keep the brunt of the moisture
plume to the west and north of the county warning area. However, we
will see some improvement in PW with values inching up to 0.6-0.8
inches for the higher elevations and over an inch across portions of
the eastern plains. On Thursday, a lee side surface low will form
over the eastern plains that will drop south with a weak influx of
air from the north. This flow will not be substantially cooler or
more moist but will help to pull some higher dewpoints over the
southern foothills with an increase in convection potential by the
late afternoon. Flow through the column will be weak so could create
slow moving storms where they form into the evening hours. Similar
story for Friday with continued increased chances for storms over
the higher terrain. Instability will be weak over the plains so
expect most of the convection to remain over the higher terrain
Thursday and Friday. Temperatures will stay higher then average with
with temperatures in the upper 90s for both days.

For the weekend the upper ridge shifts southeast bringing the
monsoon plume of moisture back over the region. Details are still
coming together but there is some agreement on a front pushing in
Saturday into Sunday. This will help with the mesoscale set-up for
convection for the weekend with increased coverage for storms both
days. Slow moving storms will increase short term flood potential
across the region and especially for the area burn scars. The
slightly cooler airmass behind the frontal push will help to bring
highs back down into the 80s with lows in the 60s.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1137 PM MDT Mon Jul 26 2021

VFR through the period. Smoke during the day will not impact
surface visibility but may impact slant visibility on approach and
so included P6SM FU during the daylight hours. Otherwise southerly
drainage wind overnight will shift around to east to southeast
during the day Tuesday.


Issued at 252 PM MDT Mon Jul 26 2021

Isolated thunderstorms in the mountains this afternoon are
expected to produce light precipitation, and only a minimal threat
of burn area flash flooding. Tuesday will be similar, with
probably even more limited thunderstorm activity and
precipitation, and the burn scar flooding threat will remain

Wednesday will see limited thunderstorm activity over the
mountains. Storms will be slow moving but the moisture supply is
limited, so the threat of burn scar flooding will still be very
low. Thursday and Friday will see both more coverage of storms and
a bit more moisture, so there will be some increase in the
threat. Saturday and Sunday look to have much more thunderstorm
activity in an environment that is favorable for heavy rainfall,
so the threat of heavy rain and burn scar flooding will be higher.




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