Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
000
FXUS65 KBOU 141533
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
933 AM MDT Fri Jul 14 2017

.UPDATE...
Issued at 917 AM MDT Fri Jul 14 2017

High pressure ridge aloft remains anchored over the region with
the main center over Southern Wyoming and a resultant light
easterly flow aloft over Northern Colorado. Unfortunately the
easterly flow is bringing in drier and warmer mid level air in
from the east and northeast. Note the 12z sounding at North
Platte which showed a much drier airmass intrusion from
700-300mb. This dryness also noted on the 12z DNR sounding with
drying in the 600-500mb layer and +2c warming at that level. This
will kill much, if not all convection chances over much of
northern Colorado. Water vapor imagery showing a pronounced swirl
over south central Colorado which may aid convection over
mountains and mainly along and south of the interstate 70 corridor
and along the Palmer Divide. High resolution models still focus
stronger storms over these areas and current forecasts reflect
this. No major changes needed.

&&

.SHORT TERM...(Today and tonight)
Issued at 410 AM MDT Fri Jul 14 2017

Hot upper ridge remains over the Rockies with deep moisture on the
south side, and shallower low level moisture further north. There
is a bit of a stable layer along with the drier air on the north
side of the ridge, which has capped convection pretty well the
last couple of days. The challenge is in the gradient, which will
lie across central Colorado. A weak trough/shear zone has formed
in the low to mid levels from southwestern Colorado into western
Kansas that marks the boundary between the very moist air to the
south and the drier air to the north. Some models lift this north
slightly today, while others do not. Currently the more aggressive
models have a bit too much moisture too far north. The exact
details will be affected by new convection later today.

In any event, this pattern means convection should be suppressed
over the northeast plains and the northernmost mountains, while
there will be a good environment for deep slow moving convection
over southeastern Colorado. The Palmer Divide region may be on the
edge of this. More aggressive NAM has Precipitable Water
increasing to around 1.6 inches by midnight tonight over Lincoln
County with CAPE of up to 1000 J/kg. The wind profile suggest a
cell motion of around 10 knots, but is also favorable for some
back building. But that would be more likely to occur on the south
side of whatever convection develops which again points to a
higher flood risk in southeastern Colorado. Further north both
the moisture and instability decrease quickly.

The organized convection over the southeast should linger much of
the night, keeping clouds on the fringe across much of central and
northeast Colorado as well, with fewer clouds on the northern
border. Forecast highs look good for today, I did lower tonight`s
lows a couple degrees in accordance with the latest guidance--
still a little warmer than this morning.

.LONG TERM...(Saturday through Thursday)
Issued at 410 AM MDT Fri Jul 14 2017

On Saturday, in spite of a broad ridge over the Great Basin and
central Rockies, it will remain unsettled especially across
eastern and southern portions of the cwa. The models still show a
weak low pressure system affecting eastern CO and western KS
especially in the morning and early afternoon, then shift this
feature south. Will keep slight chc pops in the morning, then
transition to scattered pops in the aftn. The best coverage would
appear to be along and south of the interstate 70 corridor, with
drier conditions and greater mid level stability to the north. The
ridge appears to have more influence over the region on Sunday.
The flow aloft will be weak with less thunderstorm coverage over
the region. The best chance of thunderstorms in the aftn and
evening will be over the higher terrain. The center of the ridge
shifts more to the east of CO by early next week with a weak south
to southwesterly flow aloft ov er the state. There will be enough
subtropical moisture advecting northward into CO to produce a
chance of thunderstorms in the aftn and evening, primarily over
the mountains, with more isolated coverage over the northeast
plains. High temperature on Monday and Tuesday are expected to
climb back above 90. The thunderstorms coverage may increase a bit
more across the northeast plains by the middle of next week with
temperatures dropping back into the mid to upper 80s with greater
cloud cover and possibly higher pops.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 917 AM MDT Fri Jul 14 2017

Drier and more stable mid level air will keep terminals mainly
storm free today but could see outflow boundaries from the west
and south which could shift wind directions later
afternoon/evening hours especially at APA with just a slight
chance of thunder there.  Surface winds will shift east and
southeast this afternoon at all terminals.

&&

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

$$

UPDATE...Entrekin
SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Entrekin



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.