891 
FXUS65 KBOU 120108
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
708 PM MDT Sat May 11 2019

.UPDATE...
Issued at 706 PM MDT Sat May 11 2019

Scattered showers and couple of thunderstorms tracked across 
northeast Colorado today. By mid evening when the airmass 
stabilizes, the showers will end and most of the cloud cover will 
dissipate. This is expected to lead to another cool night across 
northeast Colorado with lows in the 30s. Issued a Frost Advisory for 
most of northeast Colorado. Temperatures should be slightly warmer 
than last night. 

&&

.SHORT TERM...(This evening through Sunday)
Issued at 311 PM MDT Sat May 11 2019

Skies have become "Mostly Cloudy" across the CWA this afternoon. 
There is a bit of shower activity over the CWA with a little of 
lightning over the eastern plains. The low level winds are all 
northerly now across the plains with some gusts as high as 30 
knots. Models show the upper closed low, now centered over central
South Dakota, to move into the northwest corner of Missouri by 
18Z on Sunday. The CWA will stay in northerly flow aloft through 
Sunday. The QG Omega fields keep weak downward synoptic scale 
energy of the CWA tonight and Sunday. The northerly low level 
winds this evening should transition to their normal diurnal 
patterns late this evening and continue that way through Sunday. 
Moisture is progged to decrease by 06Z tonight, with very limited 
amounts for the CWA through Sunday. There is a bit of CAPE 
lingering around this evening over the foothills. On Sunday, there
is limited CAPE over the mountains and foothills in the 
afternoon. The QPF fields show a bit of measurable precipitation, 
mainly over the southern half of the CWA this evening. On Sunday, 
there is only a tiny bit of measurable precipitation in the 
mountains only. For temperatures, Sunday's look to be 4-9 C warmer
than this afternoon's highs. 

.LONG TERM...(Sunday night through Saturday)
Issued at 311 PM MDT Sat May 11 2019

Sunday night an upper level trough of low pressure will cover
the central and eastern U.S. with a secondary upper level low 
pressure system moving across northern Mexico. In addition, an 
upper level ridge of high pressure will stretch from the coast of 
California into the Great Basin. Colorado will lie between these 
systems under the influence of a light northwesterly flow aloft. 
This pattern will bring dry weather to all of north central and 
northeastern Colorado. 

Much warmer weather is expected Monday through Thursday as the
upper level ridge of high pressure builds and moves over the 
Rocky Mountain Region. Temperatures across the plains are expected
to be above normal with highs ranging from the upper 70s to lower
80s. Mainly dry conditions are expected through this period. 
However, there could be enough mid level level moisture, combined 
with daytime, heating to produce a few high based gusty afternoon 
and evening showers and storms mainly over the higher terrain. The
GFS suggests a boundary sagging into the far northeastern plains 
Tuesday night with increased surface moisture behind it. The GFS 
sounding has capes over 1000 J/KG and enough shear to produce one 
or two strong to severe storms late Wednesday afternoon and 
evening. However, the ECMWF and GEM solutions are lacking in 
moisture and have no QPF across the far northeastern plains. 

Thursday and Friday, the upper ridge shifts eastward into the 
Central Plains States as a large upper trough pushes into the 
western U.S. Ahead of the trough, Colorado will be under the 
influence of a southwesterly flow aloft which should translate to 
mostly dry and continued warm weather across the plains with 
isolated to scattered showers and storms in the mountains.

Cooler unsettled weather is expected on Saturday as the upper
trough moves across the region. There is some uncertainty in how
active the weather will be due to the model differences. The GFS
shows a broad upper trough moving over Colorado with a west-
southwesterly flow aloft and a relatively dry airmass at the
surface. This solution would result in isolated to scattered light
showers across the CWA. The GEM and ECMWF models are deeper with
the upper trough which would result in a better chance for
precipitation across the area. If the timing of these models is
correct, we could see the potential for strong to severe storms.
 

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 706 PM MDT Sat May 11 2019

Showers will come to an end and clouds will decrease by 03Z as the 
airmass stabilizes. Northeast winds will become light by 03Z and 
turn south-southwest by 06Z. For Sunday, mostly sunny skies are 
expected. Winds will turn northerly by late morning. Gusts to 20 
knots will be possible after 18Z. 

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from midnight tonight to 8 AM MDT Sunday for 
COZ038-042>051.

&&

$$

UPDATE...Meier
SHORT TERM...RJK
LONG TERM.....JK
AVIATION...Meier