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 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS65 KBOU 251928

Area Forecast Discussion
National Weather Service Denver/Boulder CO
128 PM MDT Sun Jun 25 2017

Issued at 124 PM MDT Sun Jun 25 2017

Have decreased pops this afternoon over most of the urban corridor
with the low stratus slow to burn off, keeping the cap in place,
as shown on ACARS soundings. Will keep a slight chance later this
afternoon into the evening based off more sun heating the Palmer
divide area and possible outflow boundaries to get above the

UPDATE Issued at 925 AM MDT Sun Jun 25 2017

A lower cloud deck has spread over much of the plains, likely part
upslope surge and outflow from this mornings convection over the
eastern plains. CIRA Simulated WRF satellite showed this nicely,
with it keeping the low stratus through about noon before breaking
up. Recent models have also decreased the amount of convection
over the far eastern plains for later this afternoon, likely from
the current convection. Have adjusted the sky cover, pops and
TAFs accordingly.

May need to adjust the high forecast temperatures for today -
depending on how long the clouds hang around.


.SHORT TERM...(Today and tonight)
Issued at 332 AM MDT Sun Jun 25 2017

Northwest flow aloft to persist today. At the lower levels, a
large surface high extends from the Northern Plains south-
southeast to the lower Mississippi region. This will keep an
easterly low level flow over eastern Colorado. The lower airmass
will remain on the moist side while the northwest flow aloft will
bring dry air at the mid and upper levels. A jet passing to the
northeast of Colorado helped produce isolated showers and
thunderstorms overnight across the eastern plains. This will shift
east of the region this morning and bring this activity to an
end. Temperatures slightly warmer and a slight increase in
moisture will improve instability today. CAPE is forecasted to
climb to around 500 J/kg. No large scale features to help trigger
convection. An easterly upslope flow may help along the foothills,
but warm mid levels will make it difficult for storms to form.
Will have isolated/slight chance pops in the forecast for this
afternoon and evening. West of the Front Range mountains, a drier
airmass in place will result in sunny skies, mild temperatures,
and dry conditions today.

.LONG TERM...(Monday through Saturday)
Issued at 332 AM MDT Sun Jun 25 2017

Upper level high pressure building over the Rocky Mountain Region
will bring mostly dry and warmer weather to north central and
northeastern Colorado on Monday. On Tuesday...a moderate westerly
flow aloft develops over Colorado as the upper ridge shifts eastward
over the Central Plains States. This pattern will allow a dry
downslope flow to develop on the lee of the Rockies...resulting in
hot and dry weather across the Front Range Urban Corridor. Further
east across far northeastern sections of Colorado...isolated to
scattered storms will be possible due to more available moisture and
instability ahead of a surface lee trough. The GFS and NAM differ
drastically in the amount of cape across the far northeastern
plains on Tuesday. The NAM shows a cape over 2500 J/KG near
Julesburg at 00Z Wednesday...with very little CIN and some
directional shear. If this verifies...a few severe thunderstorms
would be possible. However...the GFS is much drier and shows no
cape. SPC does have a slight chance for severe thunderstorms
across the far northeastern corner of Colorado on their Day 3
Severe Thunderstorm Outlook.

Wednesday and Thursday...A couple of weak cool fronts associated
with a weak upper level trough moving across the northern and
central Rockies will bring cooler temperatures to north central and
northeastern Colorado. A little more moisture and some lift from the
upper trough may result in a slight increase in precipitation
chances as well. However...the 00z GFS model run has trended weaker
with the trough and is quite a bit drier.

Models are showing some upper level ridging over the southern and
central Rockies by Saturday...resulting in a warming trend across
the CWA. There should be enough moisture around to produce a few
afternoon and evening showers and storms possible across north
central and northeastern Colorado both Friday and Saturday.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 925 AM MDT Sun Jun 25 2017

A broken ceiling around 1-2k feet has formed over much of the
area today, curing south along the urban corridor as a surface low
is east of DEN. Simulated WRF satellite shows this layer hanging
on through around 18z before breaking up. There is a slight
chance for thunderstorms 21-04Z though the best chance will be to
the west and south of the Denver area. Winds should become more
northeasterly over the next couple hours then easterly around 22Z.
The easterly flow is expected to keep clouds over the area
through the evening. After 06Z Monday, clearing is expected as
drier air moves into the area. Some MOS guidance and forecast
soundings showing possible fog under light winds across the area.
Will hold off for now putting any mention into the TAFs.




LONG TERM...Kalina
AVIATION...Meier is the U.S. government's official web portal to all federal, state and local government web resources and services.