605 
FXUS65 KBOU 010950
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
350 AM MDT Mon Jul 1 2019

.SHORT TERM...(Today and tonight)
Issued at 345 AM MDT Mon Jul 1 2019

An active weather day is shaping up for the forecast area on this
first day of July. Current satellite shows a healthy plume of 
mid/upper level moisture stretching north/northeast across the 
state. Meanwhile, the low levels had also moistened considerably 
with dewpoints running in the upper 50s to lower 60s across the 
plains, and upper 30s to lower 50s in the high country. 
Precipitable Water (PW) values had increased to around 1 inch 
along the I-25 Corridor, and closer to 1.2 inches over the eastern
plains. Meanwhile, bulk shear values will be increasing slightly 
today as an upper level speed max brushes by to our north. 

The combination of these parameters gives us a favorable set up
for storms with locally heavy rainfall, not to mention a threat of
a couple severe storms. MLCAPE is expected to push into the
800-1200 J/kg range, with values upwards of 1500-2000 J/kg
possible on the eastern plains if we see enough sunshine. Sunshine
will certainly be a large factor in the coverage, location, and 
intensity of convection today, and that's very difficult to get a
handle on at this hour. We'll likely have to wait until later 
this morning or even early afternoon to see where more sunshine 
become prevalent before refining any of these heavy rainfall or 
severe weather threats. It's clear the convective allowing/high
resolution models are struggling with this too, with many 
variations between the HRRR, ARW, NMM, NAMNEST, and HRW NSSL. The 
bottom line is any storm could produce heavy rainfall/flooding 
threat - see Hydrology Discussion below. The strongest storms 
would have potential to produce large hail and possibly even a wet
microburst given the MLCAPE and 0-6 km bulk shear increasing to 
25-30 knots. Bulk shear is lower to the south, and the tail end of
the upper level speed max should aid convective coverage tonight,
so would not be surprised to see development of a Mesoscale 
Convective System (MCS) across the plains this evening. 


Convection will decrease with eventual drying and stabilization of
the airmass from west to east through the evening and overnight
hours. 

.LONG TERM...(Tuesday through Sunday)
Issued at 302 AM MDT Mon Jul 1 2019

By Tuesday morning, the shortwave that moved around the periphery of 
a broad mid- and upper-level ridge will have pushed eastward into 
Kansas. Moisture PW values will continue to be elevated with the 
eastern plains seeing between 0.75 and 1 inch by Tuesday afternoon. 
Diurnal convection will start over the higher terrain by the 
afternoon hours and push east off the mountains and onto the plains 
by the late afternoon. Surface hi-res models are showing some 
drying over the far northeastern plains with the influence of a 
deep surface high over Nebraska. This could lead to higher 
dewpoints closer to the foothills vs further east where dewpoints 
could be slightly lower. Due to the higher moisture levels, CAPE 
values will reflect the increased instability West of a Sterling 
to Limon line with values between 1000 and 1500 j/kg. Model 
soundings show good mid- and low-level lapse rates across Denver 
metro with DCAPE values around 1500 j/kg. With PW values still 
registering 0.95, main hazards with convection will be brief 
moderate to heavy rain, gusty winds such as microbursts and some 
hail. High temperatures for Tuesday will be near seasonal normals 
with values in the mid 80s across the plains and 60s in the 
mountains. 

Wednesday will continue the drying trend with PW values dropping 
slightly across the region. Expect less convection for Wednesday 
with only isolated storms forming over the mountains. A cell or two 
could push off the higher terrain onto the plains, however CAPE and 
moisture will be minimal so storms may have trouble staying 
together. Surface winds will turn SW that will help increase 
downsloping and help temperatures reach into the 90s once again for 
the Denver Metro and areas east. Mountains will be in the 60s to 
70s. 

For Thursday, the upper low that was over the Pacific NW will track 
inland and into northern Idaho and Montana. This will keep Colorado 
in moderate SW flow aloft. A surface low in place over southern CO 
will pull in more moist SE winds that will help bring CAPE values 
across the eastern plains from 1100 up to 2000 j/kg across Phillips 
and Sedgwick counties by the late afternoon hours. If diurnal 
convection over the mountains can make it over the more stable Front 
Range and into the deeper and richer moisture of the eastern plains, 
some storms could be capable of moderate to heavy rain along with 
hail and gusty winds. 

For Friday, the models start to diverge on the synoptic set-up and 
surface triggers for storms. The upper level pattern continues to be 
from the SW with some embedded shortwaves pushing around the ridge. 
The GFS keeps things stable with minimal moisture in the mid-levels. 
The EC however has better moisture and CAPE values for Friday with 
deep layer shear up to 45 kts which could support strong to severe 
storms. At this time, will put a slight chance of convection for the 
eastern plains for Friday late afternoon and into the evening hours 
on the plains. Highs toward the end of the week will be in the 80s 
with afternoon storms possible each day. 

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 345 AM MDT Mon Jul 1 2019

Main concern will again be a round of afternoon and early evening
thunderstorms. Coverage should be higher today and storms will
pack more reduction in visibility and ceilings due to embedded
heavy rainfall. Small risk of a severe storm with hail and high
winds. Highest storm threat will be between 20Z and 01Z, so tempo
TSRA and gusty winds warranted for this period. Outside of the
storms, VFR conditions expected with fairly normal diurnal wind 
patterns. 

&&

.HYDROLOGY...
Issued at 345 AM MDT Mon Jul 1 2019

Several streams in the mountains had an extra bump last night due
to yesterday's mountain rainfall on top of melting snowpack. This
puts a few streams in interest today and tonight if we get any 
more appreciable rainfall in the basins. This includes the upper 
reaches of the Colorado River near Grand Lake, upper reaches of 
the Big Thompson near Estes Park, Williams Fork in Grand County, 
Tenmile Creek near Frisco, and St Louis creek near Fraser.

Outside of that, there is an increasing risk of heavy rainfall and
short term flooding from storms this afternoon and tonight. This
depends heavily on cloud cover and destabilization, as well as the
forward propagating speed of the storms. Warm cloud depth will be
between 4000 and 5500 feet on the plains and I-25 Corridor, so
expect fairly efficient rainers considering Precipitable Water
(PW) will range from 1 to 1.30 inches (those higher amounts over 
the eastern plains). Storm motion should only average about 8-18 
mph, with the slower movements south of I-70 where overall shear 
is weakest. Would not be surprised to see development of a 
Mesoscale Convective System (MCS) over our eastern plains to bring
a higher threat of heavier, persistent rain and thunderstorms 
there. At this time, that would favor areas roughly east of a line
from Sterling to Akron and Limon this evening. Burn scars will 
also be more susceptible to local flooding, but storm motion in 
most of our burn scar areas should be fast enough to reduce the 
risk of significant flash flooding. Therefore, no watches at the 
moment but we'll continue to monitor. 

&&

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

$$

SHORT TERM...Barjenbruch
LONG TERM...Bowen
AVIATION...Barjenbruch
HYDROLOGY...Barjenbruch