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Area Forecast Discussion (AFD)

Issued by Denver/Boulder, CO (BOU)

FXUS65 KBOU 231000

Area Forecast Discussion
National Weather Service Denver/Boulder CO
400 AM MDT Tue Jul 23 2019

.SHORT TERM...(Today and tonight)
Issued at 400 AM MDT Tue Jul 23 2019

The upper level ridge will bump up just a little more today,
centering itself over eastern Utah and Western Colorado. Current
water vapor imagery shows some drying on the northern and eastern
side of this ridge, over our forecast area. Precipitable Water
trends have been declining, with amounts down a good 0.25-0.35
inch since this time yesterday. Overall, the forecast of a little
less storm coverage and lower intensity is on track. That said,
the higher terrain and diurnally driven upslope across the Front 
Range Mountains and Foothills should still be supportive of 
relatively high coverage. Storm coverage should drop off rather 
quickly to the east including most of the I-25 Corridor where a 
stronger cap is noted, but southern Denver and Palmer Divide would
have a weaker cap with convective inhibition (CIN) only around 
20-30 J/kg, so we'll maintain our middle of the road storm 
chances there. Main threat from the storms today would be brief 
heavy rain, gusty outflow winds to 40-50 mph, and mostly small 
hail given less MLCAPE (around 600-1200 J/kg) and weak wind shear 
profile. The eastern plains will remain capped and dry. 
Temperatures will warm several degrees across the plains as cooler
surface high pressure erodes to the east. 

Activity will come to a relatively quick end this evening as the 
airmass stabilizes. We'll then see clearing skies with near normal
low temperatures.

.LONG TERM...(Wednesday through Monday)
Issued at 400 AM MDT Tue Jul 23 2019

The remainder of the week looks like a continuation of monsoonal
moisture over the state with rounds of afternoon thunderstorms
each day. Thursday appears to be the wettest day of the bunch as
cross sections show deep and weak north-northeast flow from the
surface up through middle levels which will add a weak upslope
component to the daytime warming and afternoon de-stabilization of
the airmass. The center of the upper level ridge is forecast to
remain over the Four Corners region through the end of the week
which will produce the weak flow aloft and allow the advection of
monsoonal moisture into the state. Model soundings indicate that
precipitable water values will exceed 1 inch Wednesday and
Thursday afternoon along with freezing levels above 15,000 feet
MSL. Warm afternoon temperatures will precede afternoon
thunderstorm development, with highs into the lower 90s for a few
of the days. Locally heavy rainfall will be possible wherever
thunderstorms form, but it is difficult to pinpoint any region
that will be more favored than others, so no Flash Flood Watches
for now.  

Through the weekend, the threat of heavy rain producing
thunderstorms will continue as the upper level ridge remains over
the Four Corners. Temperatures are forecast to be a little cooler
on Sunday, but that may be caused by an increase in shower
coverage. The presence of the monsoonal moisture will keep
overnight temperatures warmer than normal. The shower activity
will also hopefully help to keep fire danger levels down.  


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 400 AM MDT Tue Jul 23 2019

VFR conditions are expected through tonight, with just a slight 
risk of a thunderstorm 21Z-02Z.  Today's storm chances are much 
less than yesterday, only around 20%. There is better chance of 
some outflow/gust fronts with gusts to around 25-30 knots, most 
likely out of the west given expected storms dying as they come 
out of the foothills. However, some chance of a storm developing 
south/east of DIA with gusty southeast winds. 

Outside of any of these storm boundaries, south/southwest winds 
will become light and variable 16Z-18Z, before transitioning to 
east/northeast at 10 to 15 knots 19Z-21Z. Winds turn back to 
normal south/southwest 02Z-04Z tonight. 




SHORT TERM...Barjenbruch
LONG TERM...Dankers