Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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395
FXUS65 KBOU 291757
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1157 AM MDT WED JUN 29 2016

.UPDATE...
Issued at 1154 AM MDT Wed Jun 29 2016

Forecast on track, except for the clouds arriving from the west a
couple of hours early. Still expecting generally weak convection
over the mountains, then some stronger storms on the northeast
plains late in the day. It still looks like the main event will be
whatever develops north of us moving through in the very late
afternoon or early evening.

&&

.SHORT TERM...(Today and tonight)
Issued at 400 AM MDT Wed Jun 29 2016

CWA is mainly storm free at the time but there has been some
generation of stratus overnight across the Urban corridor and
over the Palmer Divide. Stratus expected to diminish and shift
East through the early morning hours as moisture depth is rather
shallow and drier west winds develop.

Main concerns again today revolve around the threat of severe
storms over the Northeast plains. Main change to note today over
the past 24 hours is the moisture increase across the mountains
and Western Colorado. Precipitable water values have increased
about a quarter of an inch at GJT and GOES sounder Total PW
values confirm this. Not much change in PW values across Eastern
Colorado although surface dewpoints are 3-5 degrees lower than
yesterday. Would expect a more normal start to convection over the
mountains by late morning and then beginning to drift East and
Southeast over the adjacent plains during the afternoon. Since
surface moisture is rather shallow expect some low level drying as
dewpoints lower. Forecast soundings would mainly support gusty
winds...brief rain and small hail as surface based capes drop to
under 1000j/kg. This was the thinking yesterday as well but we
did have the big storm over Denver which appeared to develop on a
narrow band of higher dewpoints and pseudo dry line over North
Denver and Boulder areas. We shall see.

High Res models today shift dry line further East across Far
Eastern Colorado...mainly from near Cope to Sterling and points
East. This might be too far East and SPC does have the slight
chance for Severe line a bit further West. Latest HRRR develops a
complex over Larimer and Weld counties after 20z but not a lot of
consistency amongst the models. Of course there is the forecasted
MCS which drops down from Wyoming and Nebraska Panhandle this
evening. Overall, best chance for severe storms will be over the
Northeast Plains with the richer low level moisture...higher capes
and stronger shear profile. Still, can`t rule out a strong storm
further West.

As in last several nights...outflow from convection will likely
result in areas of stratus developing on the plains later tonight.
Mild temperatures and fair amount of clouds will likely develop
towards Thursday morning.

.LONG TERM...(Thursday through Tuesday)
Issued at 222 AM MDT Wed Jun 29 2016

On Thursday, upper level high pressure is centered over west Texas,
with subtropical moisture flowing into Colorado from the south and
southwest. Models also show a weak cold front moving into
northeastern Colorado late morning with a moist upslope flow
developing by afternoon. NAM and GFS show the atmosphere becoming
saturated by Thursday evening, with PW`s above 1.20 inches across
the northeastern plains including Denver. In addition, models show
an upper level shortwave moving over northern Colorado through the
day. All of these ingredients should result in cooler and wetter
weather across north central and northeastern Colorado Thursday and
Thursday night. The high PW`s combined with slow storm motions
should result in areas of heavy rain. The main focus for heavy rain
and localized flash flooding looks to be over the Front Range
Foothills due to the easterly to southeasterly upslope flow. One
thing to note is that yesterday`s models showed deeper easterly
upslope flow, slightly higher PW`s along with higher QPF along the
Front Range Foothills, adjacent plains and Palmer Divide. Despite
this trend, still think we should see still see a good chance for
precipitation and areas of heavy rain.

On Friday, the upper high shifts further east into central Texas,
with the flow of subtropical moisture continuing to flow into
Colorado. The upslope flow diminishes which should decrease storm
coverage. However, a moist south to southeasterly flow at the
surface, combined with increased shear, could result in a better
chance for severe weather across the plains and Palmer Divide. Heavy
rain will also be possible as PW`s remaining above 1.10 inches.

On Saturday, models show a shortwave moving across Colorado, with a
little bit of drying at the surface and aloft. However, there should
be enough moisture, instability and lift from the short wave to
produce scattered afternoon and evening showers and storms across
the region.

On Sunday, the upper ridge of high pressure re-establishes over the
desert southwest, with a drier westerly flow aloft over the Rocky
Mountain Region. This pattern should result in warmer and drier
weather across north central and northeastern Colorado. There should
still be enough moisture around, combined with daytime heating, to
produce isolated to scattered afternoon and evening showers and
storms, mainly over the higher terrain.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1154 AM MDT Wed Jun 29 2016

VFR through this evening. There is a chance of thunderstorms in
the late afternoon and early evening with brief variable winds to
30 knots the main threat. There may be some low clouds early
Thursday morning with MVFR or possibly IFR conditions for a few
hours. There is some uncertainty about the formation of these
clouds.

&&

.BOU Watches/Warnings/Advisories...
None.
&&

$$

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



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