594 
FXUS65 KBOU 100949
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
349 AM MDT Sat Aug 10 2019

.SHORT TERM...(Today and tonight)
Issued at 203 AM MDT Sat Aug 10 2019

Main story today is for an increase chance for thunderstorms 
across much of the area along with another marginal threat for 
severe storms on the plains. 

Layered precipitable water 500-300mb and 700-500mb products showing 
the plume of deeper moisture has worked back up into northern 
Colorado this morning. Integrated PW values confirm this increase 
with values again nearing an inch of precipitable water, which is an 
increase of around a quarter of an inch increase in the past 12 
hours. There is also a decent swath of mid and high level clouds 
covering much of the northern mountains.  Surface dewpoints are 
currently ranging from the 50s along the Front range to the 60s 
across the far northeast plains with some increase in dewpoints 
still by later today. By later this afternoon, PW values will range 
from 1.25 over the Front Range to near 1.50 inches over the far 
northeast plains. 

Temperatures today expected to be a bit cooler with more cloud cover 
and upslope flow up to 550 mb.  Model CAPE values generally in the 
1000-2000j/kg, highest over the eastern plains with dewpoints in
the lower 60s. Hard to pinpoint the greatest threat of storms
today as high resolution models are all of the board, but expect 
somewhere along and south of the I-76 would be the best consensus 
for now and will play the higher pops there. Main impact will be 
heavy rain with rainfall rates up to 2 inches in less than one 
hour. Again marginal large hail threat given the high CAPE values 
and moderate mid level flow. 

.LONG TERM...(Sunday through Friday)
Issued at 203 AM MDT Sat Aug 10 2019

Sunday will be very moist for Colorado as a plume aloft continues
to drift overhead while a weak boundary backs into northeastern
Colorado with rich moisture pooled along it. The cloud cover and
warm temperatures aloft may be a limiting factor in convection for
much of the day, but it should get warm enough for surface based
convection late in the day, especially in a likely convergence
zone along the old boundary. CAPEs may be lower over the western
part of the area (500-1000 J/kg) due to the warm air aloft, but
with dew points in the 60s expected over the eastern part of the
plains, CAPEs there look to be in the 2000-3000 J/kg range. There
is also pretty substantial deep layer shear for this time of year,
around 50 knots. This will create a favorable environment for
supercells. The low level winds will likely not be that favorable
for tornadoes, though given the likely updraft strength, local
modification of the environment could well help create sufficient
storm inflow. Large hail and damaging winds will be possible, with
the heavy rain threat reduced by quick storm motions despite
precipitable water ranging from 1 to 1.75 inches on the plains.
There will be a lower but nonzero severe risk close to the Front
Range. 

The thunderstorms we do get should move right along with clearing
Sunday evening. Much drier air aloft will move in by Monday,
though there will still be some low level moisture to mix out and
generate a much lower level of diurnal convection on Monday. It
also looks like there is a shortwave passing north of us that
could help along some marginal convection. 

For the rest of the week, there is westerly flow aloft across the
northern Rockies while we're on the edge of the seasonal ridge
across the south. This should lead to a warmer and drier period,
with highs in the 90s on the plains and only isolated storms. A 
trough over the northwest will lead to southwesterly flow aloft by
the end of the week with some increase in speeds. 

Some model runs put us in a zone of very dry air which could 
raise fire weather issues Thursday or Friday, while other runs 
have this zone further north and bring better moisture into 
southern Colorado and would probably keep us with at least 
isolated storms and low but not super dry humidities. Fuels will 
be drying again, but are still rather moist in most mountain areas
and parts of the plains...with some drier areas.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 203 AM MDT Sat Aug 10 2019

Expect a better chance for thunderstorms this afternoon at local
terminals, especially between 21-01z. Heavy rain and gusty winds
the main threat with potential ILS conditions with heavy rain.
Surface winds expected to shift to the northeast this afternoon.
Improving conditions this evening. 

&&

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

$$

SHORT TERM...Entrekin
LONG TERM...Gimmestad
AVIATION...Entrekin