Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 181649

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1049 AM MDT Tue Jul 18 2017

Issued at 1047 AM MDT Tue Jul 18 2017

Shortwave moving through the northern state border brought early
morning light showers. This shortwave will continue pushing east
through the day to interact with the convergence boundary
forecasted to set up over the eastern plains. Winds are already
turning easterly over the eastern CO border, which will advect in
higher theta-e values, helping to fuel the expected stronger
storms forecasted. Shear will also be higher over the northeastern
corner of the state, though not great - so while stronger storms
are expected, not confident we`ll see severe strength at this
point. Main impacts will be hail and strong gusty outflow winds.
Have updated the near term PoP grids to reflect current conditions
and into the slightly higher PoPs for the mountains sooner than

Have decreased PoPs over the far northern mountains as drier and
more subsident air behind the shortwave will sink into the state.


.SHORT TERM...(Today and tonight)
Issued at 246 AM MDT Tue Jul 18 2017

Upper level high will be centered to the southeast of Colorado. A
weak westerly aloft is expected to prevail over northeast
Colorado today. Satellite imagery showing a good amount of mid
cloud over eastern Utah and western Colorado at this time. Not
sure if the clouds will move over eastern Colorado later this
morning, but moisture should at least increase with precipitable
water values topping an inch east of I-25 and north of I-70. CAPE
is forecasted to reach 300-800 J/kg. Expect storms to produce
heavy rain and gusty outflow winds up to 50 mph. A severe storm or
two can`t be ruled out over the northeast corner where shear will
be little better. Scattered storms are expected to begin shortly
afternoon over the higher terrain with isolated storms possible
starting mid afternoon east of the higher terrain. Convergence
along a boundary from Julesburg to Akron to just west of Lincoln
my help trigger storms mid afternoon. Airmass will remain warm
today with highs in the mid to upper 90s over northeast Colorado.

.LONG TERM...(Wednesday through Monday)
Issued at 246 AM MDT Tue Jul 18 2017

The center of the upper level ridge is expected to shift eastward
on Wednesday, located near the Oklahoma and Texas Panhandles at
that time. Sub-tropical moisture will make its way into western
Colorado with the best chance of afternoon and evening
thunderstorms over the mountains. Temperatures at 500 mb will be
around -4c Wednesday aftn, which will translate to mid to upper
90s at the surface. Thursday through Saturday, the upper level
ridge will continue to slowly migrate eastward, settling over the
central plains states. A weak south-southwesterly flow aloft will
open up Colorado to a better stream of sub-tropical moisture.
Scattered thunderstorms will be possible over the entire cwa in
the afternoon and evening. Temperatures will not be as hot with
the warmer mid level temperatures moving into the central plains
as well. Due to the weak storm motions, the main threat from the
storms will be localized moderate to heavy rain showers. The ridge
will flatten a bit over the weekend as a weak embedded trough
moves over the state. This may help to enhance the shower and
thunderstorms coverage a bit along with slightly cooler temperatures.
By early next week, the ridge is progged to rebuild over the west
allowing for drier and hotter conditions to return.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday)
Issued at 1047 AM MDT Tue Jul 18 2017

VFR conditions are expected through tonight. Scattered
thunderstorms expected over the higher terrain west of Denver
by 18Z will have a hard time pushing too far east. However isolated
thunderstorms will be possible over the Denver area after 20Z.
Outflow from thunderstorms will likely push across the Denver
airports and produce wind shifts. If a storm directly hits a
terminal, brief heavy rain and wind gusts to 45 knots will be
possible. Chance for storms will end by 03Z. Winds are expect to
turn northeasterly around 18Z. After a few possible wind shifts
due to convection, winds are expected to settle at a southerly
drainage direction around 06Z, then likely remain south to
southwesterly Wednesday morning.




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