Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/07/19

Area Forecast Discussion

National Weather Service Denver/Boulder CO

 800 PM MDT Sat Jul 6 2019

.UPDATE...
Issued at 800 PM MDT Sat Jul 6 2019

Storms are rolling east/southeast from Wyoming, but have recently
weakened a little, perhaps because they`re running into slightly
cooler boundary layer air. We still think there is a threat of
severe thunderstorms roughly along/north of a line from Wellington
to Akron, with the highest probabilities of storms over the
northern border area through the midnight hour. The increasing low
level jet could be the kicker of additional storm development
over the northeast plains late this evening. We`ll look at
possible severe thunderstorm watch extension and expansion to the
east. Otherwise, we were able to clear more of the Denver area and
Palmer Divide from the severe thunderstorm watch, as 00Z sounding
shows airmass just a bit too capped to support surface based
strong/severe convection. There is one thing that could still pop
a few strong/severe storms along the Front Range, and that would
be an outflow boundary pushing out of the Wyoming/far northern
Colorado convection. It`s a small chance, but a chance nonetheless
since we did not tap into much if any of the 1000-1500 J/kg
MLCAPE this afternoon along the Front Range.

UPDATE Issued at 546 PM MDT Sat Jul 6 2019

Storms have been paltry so far, and a look at the latest aircraft
data departing DIA shows a pretty strong stable layer near 725 mb
that is effectively capping off the I-25 Corridor. Will be nice to
see the 00Z Denver sounding. There were still a few storms on the
plains and trying to get going over the mountains, but the main
chance of any severe weather is shifting to the north and east.
There is some threat with the storms firing over Morgan county and
spreading eastward, but the main threat of more organized severe
weather appears to be shaping up from the storms dropping
east/southeast from Wyoming. These are severe already, and should
try to organize into a Mesoscale Convective System (MCS) as they
feed on an intensifying low level jet this evening. Most of these
should remain north of a line from Wellington to Akron, and will
be most likely near the Wyoming border cutting through the
northeast corner of the state. Right moving severe supercells
with very large hail could definitely be in the picture given
existing MLCAPE near 1500-2000 J/kg and stronger shear profile to
the north. We`ll keep higher PoPs and severe risk there, but have
dropped the chance of storms in/around Denver.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 322 PM MDT Sat Jul 6 2019

Storms developing over southern Jefferson County at this time. Two
separate areas focused on by the High Res models this afternoon
and evening. The first area will around the Denver area including
points mainly south and east. Main concern will focus for severe
will be around this areas. Weak cyclonic circulation as well
around Denver which could enhance the potential for severe
thunderstorms. RAP forecast soundings indicate CAPEs around 1200
j/kg with favorable directional shear as well. Precipitable water
values still close to 0.80 inches as well. Later this evening,
another area of thunderstorms is forecast clip the northeast
corner of the forecast area around 03z. Higher CAPES/greater shear
in this area. Potential for a weak tornado or two there as well.
Most of the cwa has been under a jet max this afternoon which
appears to have capped some thunderstorm development, but this
will shift eastward this evening which aid deep convection.  On
Sunday, the flow aloft will remain southwesterly with continued
potential for thunderstorms in the afternoon. CAPE values still
healthy so potential exists for another period of severe
thunderstorms with CAPES 1400 around Denver to 2400 j/kg over the
northeast plains. Higher CAPE and weaker shear, but temperatures
will be warmer with highs around 85. Expect the storms on Sunday
to be more pulse type cells.

.LONG TERM...(Sunday night through Saturday)
Issued at 322 PM MDT Sat Jul 6 2019

Medium range models continue to show a couple more days of moist
southwesterly flow aloft which will set up each afternoon for
rounds of afternoon and evening thunderstorms. Monday looks like
it will be the last afternoon of highest coverage of thunderstorms
as the flow aloft turns more westerly on Tuesday that drops the
mid-level moisture a little bit. The GFS is stronger than the
ECMWF with the drying effects, so Tuesday and Wednesday will still
need the mention of at least some afternoon thunderstorms. Cross
sections from the NAM show strong drying Tuesday morning with flow
at mid levels around 20 knots, but by Wednesday night a low level
surge of northeasterlies and increasing moisture appear to be on
their way. The ECMWF backs up this scenario. With all of the
ingredients necessary for storm formation in place over northeast
Colorado through the majority of the week, the cycle of afternoon
and evening thunderstorms will remain in the forecast.
Temperatures will reach the mid 80s to mid 90s each afternoon.
Each day will need to be assessed with regard to the threat of
heavy rainfall. By the end of the week, the upper ridge looks to
be centered over the Four Corners area which typically leads to
weak flow aloft across northern Colorado. Weak flow patterns and
slow moving thunderstorms go hand in hand, so if precipitable
water values increase, then the threat of heavy rainfall will also
increase.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 800 PM MDT Sat Jul 6 2019

Storm threat is low over the Denver area airports due to a stable
layer noted on the aircraft data moving in/out of Denver and the
00Z Denver sounding. We still see a small chance of thunderstorms
if an outflow boundary from the southern Wyoming/far northern
Colorado convection moves into the Front Range.

Otherwise, low level moisture could slip back into KDEN late
tonight/early Sunday with redevelopment of a Denver cyclone or
convective push from the the north and east. So there`s a risk of
stratus and IFR/MVFR ceilings 11Z-15Z. Scattered thunderstorms
possible Sunday afternoon after 21Z.

&&

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

$$

UPDATE...Barjenbruch
SHORT TERM...Cooper
LONG TERM...Dankers
AVIATION...Barjenbruch