Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 161020

Area Forecast Discussion
National Weather Service Denver/Boulder CO
420 AM MDT Wed May 16 2018

.SHORT TERM...(Today and tonight)
Issued at 420 AM MDT Wed May 16 2018

Warmer and drier air will be moving over Colorado today. This
should cap convection, even over the mountains where lightning was
limited to the east slopes yesterday. There still could be some
convective clouds late in the day, but the chances of lightning or
measurable rain are too low to mention.

The situation is not as clear cut near the eastern border, where
some low level moisture will remain and the cap is not as strong.
Still expect nothing this afternoon. Overnight, southerly boundary
layer winds will increase moisture and could produce a developing
convergence area somewhere along the eastern border. Soundings
near the eastern border have CAPEs around 1000 J/kg with CIN under
50 J/kg by 12z. Still not sure if there will be enough convergence
for a trigger, but a couple strong storms are possible. More
likely, this will just be setting the stage for Thursday`s action.

Forecast temps are near guidance and look good.

.LONG TERM...(Thursday through Tuesday)
Issued at 420 AM MDT Wed May 16 2018

Thursday and Thursday night, upper level ridge axis will shift
into Kansas/Nebraska with a southwesterly flow aloft over the cwa.
The GFS shows a weak ripple in the flow Thursday morning,
possibly enough to spawn isolated thunderstorm over the far
northeast plains in the 12-18z period. In the afternoon and
evening, weak qg ascent will be over the region, with a sfc low
over eastern CO. Moist southeasterly winds will increase in the
afternoon, with the computed boundary layer CAPES around 2500
j/kg. The strongest low level convergence will be along the
Cheyenne Ridge, so best chance of severe thunderstorms would
appear to be along and north of a Fort Collins to Akron line
through Thursday evening. Friday and Friday night, the upper
trough will be located along the Nevada/Utah border with weak to
moderate mid level qg ascent developing Friday afternoon and
Friday night. Still abundance of CAPE around 3000 j/kg and
precipitable water around one inch. Suffice it to say, the threat
of severe thunderstorms will continue Friday afternoon and Friday
evening. More clouds/showers will drop max temperatures in the mid
70s. Friday night, the surface low will strengthen and center
itself over sern CO by 12z Saturday. The snow level by that time
will be around 10500 feet, with accumulating snowfall likely
Friday night into Saturday morning. Snow amounts possibly in the
3-6 inch range, with the greatest accumulation in zones 31 and 33.
A cold front will makes it way southward across the cwa Friday
night. The heaviest rain and strongest thunderstorms potential
will remain along the northern border, but the threat of light to
moderate rain across the rest of the cwa will increase into
Saturday. The mid level trough axis is progged to slide across the
cwa Saturday morning, with more rain vs thunderstorms on
Saturday. The flow aloft will be fairly weak with a more stable
post-frontal airmass over the northeast plains. Best chc of tstms
Saturday aftn and evening will be over the higher mountains. Highs
on Saturday will only reach the mid 50s. Sunday and Sunday night,
weak mid level ridging during the day may give way to another
potential disturbance Sunday night. Best chc of showers at that
time may be south of Interstate 70. Temperatures on Sunday will
rebound a bit, warming back into the mid 60s. Early next week, the
warming trend will continue with enough moisture to produce a
chance of afternoon and evening thunderstorm each day.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 420 AM MDT Wed May 16 2018

VFR through tonight.




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