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fxus65 kbou 160232 

Area forecast discussion
National Weather Service Denver/Boulder Colorado
832 PM MDT sun Jul 15 2018

issued at 823 PM MDT sun Jul 15 2018

Heavy rainfall threat has diminished over the past hour so have
cancelled the Flash Flood Watch. Heaviest rain has now shifted
south and east of Denver where there is still some locally
moderate to heavy rain possible through 10 PM. Much drier air
continues to work southward across northern Colorado as upper
level trof moves across the area. Clouds and showers will continue
to decrease from north to south through the night. With some
clearing and residual moisture could see some lower stratus
redevelop later tonight along with some patchy fog, especially
north and east of Denver. Drier and warmer on Monday but still
enough moisture for scattered storms, mainly higher terrain.
Overall, have quickened the ending of showers and skies clearing
for the forecast this evening.


Short term...(this evening through monday)
issued at 300 PM MDT sun Jul 15 2018

Thicker Post frontal clouds pushed into the Front Range urban
corridor today to keep in much cooler temperatures and stable
conditions early on today. This helped dissipate any activity
coming off the high terrain. However, the sunnier areas east of
the area allowed for storms to quickly form. Outflow pushing west
has kicked off weak convection and now some clearing of the Post
frontal stratus of this morning, as evidenced in visible
satellite. Better storm initiation over the central mountains is
expected to move northeast. This may time well with the clearing
to bring the expected heavy rain producing thunderstorms over the
foothills and Palmer Divide area, but it'll really depend on how
warm the surface temperatures get. Believe we'll still see some
good storm coverage, but not sure we'll get warm enough for the
higher cape values that would give more of a possibility for flash
flooding due to heavy rain. Precipitable water values are up near
1.31-1.39 inches, above the Max for the day but still below the
record Max value of 1.49 for the month for Denver. Still, any
storm that does get going will be efficient rain producers and still
have the chance to produce heavy rain.

Stream of higher precipitable water and upper level disturbance
will push southeast tonight but slightly slower than forecast,
have kept in pops through the night over the far eastern plains.
Several models targeting areas near and east of dia for heavy rain
this evening, then moving it east, with less potential for heavy
rain with loss of heating and weaker dynamics after midnight. As
heights aloft rise, and drier air works its way in, expect warmer
temperatures tomorrow with isolated to scattered afternoon
convection. These storms will have much less potential for heavy
rain. May stay slightly capped around the urban corridor with
warming mid levels.

Long term...(monday night through sunday)
issued at 320 PM MDT sun Jul 15 2018

Zonal flow will cover the County Warning Area Monday night into Wednesday with
flat upper ridging in place. There is an upper trough well to our
north and northeast Tuesday night and Wednesday. 50 to 65 knot
northwesterly flow aloft is in place Wednesday afternoon and
night. There is little of note concerning synoptic scale energy
for the County Warning Area. There is weak subsidence later Tuesday night and
Wednesday. The low level winds will be dominated by weak normal
diurnal patterns Monday night through Tuesday. Wednesday and
Wednesday evening look to have downsloping winds, with drainage
Wednesday night. For moisture, the precipitable water progs have
0.60 to 1.50 inch west to east across the County Warning Area Monday night and
Tuesday morning. Values come up into the 0.75 west to 1.80 inch
range east Tuesday afternoon into the evening. Values decrease
into the 0.30 west to 0.75 inch range east on Wednesday and
Wednesday night. Cape is pretty high over much of the County Warning Area Monday
evening. It is pretty good late day Tuesday, especially over the
northeast corner. By Wednesday, cape is significantly lower, with
some over 1000 j/kg over the far northeast corner. For pops, will
go with 20-50%s Monday evening and again Tuesday afternoon and
evening. No pops anywhere for Wednesday. For temperatures,
tuesday's highs warm up 1-3 c from monday's. Wednesday's highs
are 2-6 c warmer than tuesday's. For the later days, Thursday
through Sunday, the upper ridge migrates eastward into and over
Colorado Thursday and Friday, then it stays over the state all
next weekend. The flow aloft is west-northwesterly and fairly
weak all four days. Moisture is sparse Thursday and Friday. It
increases a bit next weekend. Temperatures will be above seasonal
normals all four days.


Aviation...(for the 00z tafs through 00z Monday evening)
issued at 823 PM MDT sun Jul 15 2018

Improvement noted at kden and kbjc as showers have mainly pushed
south. Apa still under IFR conditions in the light rain but will
also be ending there between 03-4z. Hi resolution models showing
potential low clouds/patch fog developing later tonight and early
Monday morning at bjc/den and will introduce that possibility but
not overally confident.


issued at 300 PM MDT sun Jul 15 2018

Precipitable water values are currently 0.31-0.39 inches,
exceeding the historical maximum for the day (1.18 at denver), and
close to the Max for the month (1.48 inches). Thick low level
clouds has brought more stable conditions to the urban corridor
than forecasted, but the airmass will allow for storms and even
showers to be efficient rainfall producers. Storms should be
moving along at 15-20 mph, but this may be offset by sufficient
instability and warm cloud depth to produce very heavy rainfall
with storms. We could see rainfall rates up to 2 inches per hour,
so even if a storm only last 30 minutes we could see some flooding
issues in burn scars and urban areas. There will also be low
level convergence and potential for numerous thunderstorms over
Douglas and Elbert counties, so heavier rainfall amounts will be
possible there. Even though the Flash Flood Watch likely started
too early at noon, will leave it in place for the foothills
(mainly burn scars), Palmer Divide area and areas in and around
Denver for the potential later this afternoon into the evening.


Bou watches/warnings/advisories...


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