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Area Forecast Discussion (AFD)

Issued by Denver/Boulder, CO (BOU)

FXUS65 KBOU 201036

Area Forecast Discussion
National Weather Service Denver/Boulder CO
436 AM MDT Tue Aug 20 2019

.SHORT TERM...(Today and tonight)
Issued at 307 AM MDT Tue Aug 20 2019

An upper level ridge will continue over the area with weak 
southwest mid level flow.  At the sfc, low pres will extend from the 
front range into sern CO.  This will allow fow the low level flow to 
be more easterly by aftn, however, main cold front won't move into 
nern CO until this evening.  Thus expect another hot day over the 
plains with highs in the 95 to 100 range.  Record high at Denver is 
99 so it could be tied.

Meanwhile, as for tstm potential, there isn't much agreement among 
the models as to what may transpire over the plains.  The ECMWF 
keeps most activity over the far nern plains while the GFS has 
activity closer to the foothills.  The hi res data is just as 
confusing with varying solutions as well. Overall, will keep pops
in the chance category, except closer to the WY-NE border for 
tonight, where this some agreement for better tstm coverage. Over
the higher terrain there will be some widely sct high based 
activity this aftn into the early evening hours. 

As for severe potential MLCAPE will be above 2500 j/kg over the
far nern plains late this aftn into this evening. Mid level flow 
is only around 15 kts but with decent cape can't rule out isold 
severe storms. Furthermore with hi theta-e values in the
850-700 mb layer and weak flow aloft certainly could see very 
heavy rainfall with the storms as well this evening closer to the 
WY-NE border.

.LONG TERM...(Wednesday through Monday)
Issued at 430 AM MDT Tue Aug 20 2019

Models show upper ridging over the forecast area Wednesday 
through Thursday night. There is a weak upper trough over the 
Great Basin through much of that time. There is weak upward 
synoptic scale energy noted on the QG Omega fields Wednesday and 
Wednesday night, with neutral energy progged Thursday and Thursday
night. The low level wind and pressure fields have easterly winds
on Wednesday and Wednesday evening then weak normal drainage 
patterns overnight. Southeasterlies are expected on Thursday, with
more drainage Thursday night. Concerning moisture, it increases 
on Wednesday and Wednesday night with precipitable water values in
the 0.75 to 1.25 inch range for the plains and lower foothills. 
There is only slightly drying on Thursday, but more drying 
Thursday night. CAPE values are pretty decent Wednesday and 
Wednesday evening over the CWA east of the divide. On Thursday, 
CAPE is even higher for the plains, but then values decrease 
significantly by Thursday evening and overnight. Lapse rates on 
the cross sections show a pretty decent low level cap in place 
over the plains for much of the Wednesday with the new airmass in 
place. However, above 700 mb, lapse rates are pretty steep. The 
QPF fields have fairly decent amounts of measurable rainfall for 
the CWA Wednesday afternoon through the evening. Same goes for 
late day Thursday, with just a tad less than the previous day. 
Will go, or leave in 30-60% pops late day Wednesday and 20-50% 
pops late day Tuesday. For temperatures, Wednesday's highs are 
3-7 C cooler than today's expected highs behind a cold front that 
is progged for the CWA later this evening. Thursday's readings 
come back up 1-4 C for much of the CWA. For the later days, Friday
through Monday, the upper ridge flattens on Thursday and Friday, 
with the upper ridge building back into Colorado from the due west
over the weekend. Models show it to be pretty dry all four days.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 307 AM MDT Tue Aug 20 2019

Light west to southwest winds will continue thru 15z and then become 
light northerly.  By early aftn they will become easterly.  There 
will could be a chc of higher based tstms from 23z thru 03z.  These 
storms may produce gusty winds up to 50 mph with erractic directions 
as well.  Overnight a cold front will mover across after midnight 
with winds becoming northerly.  Could see some MVFR ceilings late 
tonight after 09z.


Issued at 307 AM MDT Tue Aug 20 2019

Elevated fire danger will continue over the higher terrain and
along the front range today due to low humidities and hot 
temperatures. However winds will remain generally light.