Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 291647
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1047 AM MDT FRI JUL 29 2016

.UPDATE...
Issued at 1040 AM MDT Fri Jul 29 2016

Good low level moisture is in place again today but without the
multiple outflow surges we had yesterday the plains should warm up
more today. Seeing that somewhat already with the low clouds near
the front range burning off. There has been a persistent area of
forced weak convection out near akron with no lightning and this
area should gradually diminish. There is an east to west smoke
layer from the beaver creek fire that is moving southward now
crossing boulder to morgan counties. Denver morning sounding has
quite a worked over lower level but is quite moist. above the
boundary layer it remains quite warm and unstable with a dry
adiabatic lapse rate, so plenty of potential instability but once
again well capped and will likely be tough for any convection to
go on its own on the plains. There is a weak Denver Cyclone in
place but it is not very organized and so any forcing along its
boundary which will be in the vicinity of DIA is likely to be too
weak. That leaves storms forming on the higher terrain as a
likely source for potential storms later this afternoon and this
evening. With 30 to 40 knots of nw flow at and above 500 mb
enough shear for longer lived supercell storms should they hold
together, hence the slight risk from the storm prediction center.

Convection allowing models (NAM Nest and HRRRs) both show late
afternoon storms over the cheyenne ridge by late afternoon. Both
versions of the HRRR (last couple of runs at least) hold some
storms together with long lived cells moving south and threatening
dia around 03z. Similar development in the nam nest moves off the
cheyenne ridge and dies off quickly with nothing across the plains
this evening. Certainly both scenarios are possible but with
warmer temperatures today have to think the HRRR solutions are
not out of line. Large hail and strong winds biggest threat while
tornado threat while less is there as well given vertical shear.

&&

.SHORT TERM...(Today and tonight)
Issued at 350 AM MDT Fri Jul 29 2016

Moist low level air remains over the plains with much drier air
west of the Front Range. Drier air aloft will be moving in from
the west today, but a light easterly flow at low levels will help
maintain some moisture on the plains. There may be some mixing out
of the moisture close to the mountains. The drying aloft will
allow for some sunshine before convective cloudiness increases
again. Meanwhile there is a little shortwave producing some storms
in the northeast at this time that should be exiting by mid
morning. Another wave will move from Montana towards Nebraska
tonight dragging a bit of lift over the northeast plains this
evening. This will help keep the upslope winds going, and also
help with any weak capping that might remain. Not real clear on
the timing of the forcing mechanisms but leaning toward a few
afternoon storms but most of the activity in the evening again.
CAPEs will probably be around 1000 J/kg or maybe even a bit less
over the western part of the area due to the bit of drying. Best
areas with enough heat and more moisture could approach 2000 J/kg.
Still adequate shear, so it looks like another day of strong to
severe storms though the coverage again could be limited by the
need for the extra forcing due to marginal temperatures. Once
again large hail should be the main threat with just a low risk of
damaging winds or enough rain to cause minor flooding. With a more
southerly component to surface winds there could be a bit more of
a tornado threat this evening, but we will still be working with a
pretty linear shear profile so this threat seems small. Decreasing
activity later tonight, though with the moisture and maybe still a
little lift there could be a few lingering storms again.

West of the Front Range little or no thunderstorm activity in the
drier air. Breezy again with low humidities, but not up to red
flag conditions. Should still be an active day for the Beaver
Creek fire which has been very active on warm dry days with
moderate wind speeds, so expect continued smoke spilling into
Larimer county and a solid plume to redevelop in the afternoon.

.LONG TERM...(Saturday through Thursday)
Issued at 350 AM MDT Fri Jul 29 2016

The upper ridge is centered over the south Saturday and Saturday
night. Some of it stays to our southwest, but a strong portion is
over the southeastern United States Sunday and Sunday night. The
QG Omega fields have benign synoptic scale energy for the CWA all
the periods. The boundary layer winds will adhere to standard
diurnal patterns through Sunday night. Moisture is limited late
day Saturday with more late day Sunday. Precipitable water values
range form 0.25 west to 1.00 inch east late day Saturday. They
increase to 0.75 to 1.30 inch for late day Sunday. There is a lot
of CAPE progged for most of the CWA late day Saturday and Sunday.
The lapse rates are steeper Sunday then on Saturday. There is
limited measurable rainfall on the QPF fields for late day
Saturday, with the mountains having the most. There is somewhat
more for all the CWA late day Sunday. For pops, "slight chance"s
will do in the mountians only late day Saturday. Will increase
them for late day Sunday, with "chance"s in the high county and
"slight chance"s out on the plains. For temperatures, Saturday`s
highs are 1-4 C warmer than today`s highs. Sunday`s highs are a
tad cooler than Saturday`s with more clouds expected. For the
later days, Monday through Thursday, models migrate the upper
ridge center to the southeast of Colorado later Tuesday through
Thursday. There is pretty decent mid and upper level moisture
progged all four days. For the most part, will go with 20-40% pops
for the late day periods.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1040 AM MDT Fri Jul 29 2016

Weak Denver Cyclone which will make dia winds a bit tricky though
for now remain light and variable. Threat for potential strong
storms would likely be after 00z and maybe even 02z and bigger
threat at dia than at apa or bjc. Right now tomorrow looks drier
although this could change since likely decent low level moisture
will still be around.

&&

.BOU Watches/Warnings/Advisories...
None.
&&

$$

UPDATE...Szoke
SHORT TERM...Gimmestad
LONG TERM...RJK
AVIATION...Szoke



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