Area forecast discussion 
National Weather Service Denver/Boulder Colorado 
1042 am MDT Monday Aug 3 2015 


Update... 
issued at 1034 am MDT Monday Aug 3 2015 


No big changes planned to the going forecast. Weak qg lift 
associated with the upper trough is expected to continue through 
today and into the evening over most of the County Warning Area with the far 
northeast corner seeing the last of it late tonight. At the 
present time there is much more cloudiness than precipitation so 
solar heating is not doing much just yet. However...satellite data 
is showing a few more breaks developing recently so this should 
help get convection rolling as the day wears on. With marginal 
instability and respectable precipitable water numbers still 
expecting mostly rain from the storms...some of which could be 
pretty decent. 


&& 


Short term...(today through tonight ) 
issued at 310 am MDT Monday Aug 3 2015 


Weather trend for today is an increase chances of showers and 
storms along with a bit cooler temperatures. Water vapor showing 
upper low and trough rotating north and northeast across Utah early 
this morning. The main low will continue northward into far 
western Wyoming later today while southern extent of trough will 
slide across Colorado later today and tonight. There is some weak 
to moderate qg ascent with this trough and will aid to shower 
development. In addition...precipitable water values which are currently just 
under an inch will increase to over an inch by afternoon. Given 
the cloud cover temperatures will be cooler while instability will 
be limited as well. Hi res models are differing on storm strength 
today as rap really dries out the low levels on the plains which 
appear overdone. The NAM indicates surface based convective available potential energy of 
700-1500j/kg on the plains. Severe threat appears low but could 
see an isolated severe with damaging winds. Main threat today will 
be heavy rain with storms given high precipitable water values. 


Trough axis slides across eastern Colorado later tonight with 
showers and storms diminishing from west to east. There is some 
modest subsidence that develops behind the wave late in the night 
while cross sections showing decent cross barrier flow of 30 to 
50kt at mountain top level. Even a mountain top stable layer 
spells some gusty winds developing on The Divide and higher east 
slopes. Could see some gusts from 30 to 45 miles per hour later tonight over the 
Front Range. Clearing skies elsewhere so cooler overnight low 
temperatures. 


Long term...(tuesday through sunday) 
issued at 144 am MDT Monday Aug 3 2015 


On Tuesday...precipitation chances should quickly diminish from west-to-east 
across the high country and nearby High Plains during the early 
morning hours as drier...stable air sweeps in on west/northwesterly winds behind 
the departing shortwave trough. However the northeast corner of the 
County Warning Area will probably continue to feel the affects of this system 
throughout the day and perhaps into the early evening hours in the 
form of clouds and isolated showers/T-storms in the morning...and 
scattered T-storms in the afternoon. Its possible an upright line of 
T-storms capable of strong gusty winds and large hail could race sewrd 
across Logan...Sedgwick and Phillips counties sometime during the 
middle to late afternoon hours as the 700-500mb trough axis swings by. As 
the saying GOES...beware of northwest flow. Next...the past few days 
models indicated cooler temperatures on Tuesday. Not so anymore. Latest MOS 
temperature guidance now indicates a 2-3 degree c warmup over readings on Monday. 
Gusty downslope flow off the Front Range and greater sunshine two 
big reasons for the reversal and near average temperatures. Cross sections 
indicate 35-50kts cross-barrier flow Tuesday morning. This could 
result in middle/upper East Slope wind gusts of 35-55 miles per hour. Should see 
wind speeds gradually diminish through the afternoon with 
increased mixing. 


By Wednesday...strong upper level ridging over the central/southern Rocky 
Mountain region will continue to warm and dry the airmass over 
Colorado. Still cannot rule out a few late day high based gusty T- 
storms over and near the Front Range. Otherwise expect a dry and 
mostly sunny day with above average temperatures and lighter winds. 


Wednesday night into Thursday...models show the upper ridge flattening and 
shifting east of Colorado. The shift is in response to a progressive 
shortwave trough which models show racing east-sewrd over the northern Rocky 
Mountain region during the Thursday/Thursday night time period. The resulting zonal 
flow over northern Colorado will further lower dewpt/precipitable water values and likely 
inhibit convection with strengthening of the middle-level cap. However 
by evening could see a weak cold front race sewrd across northestern Colorado. 
Its possible weak forcing for ascent and directional shear along 
this frontal boundary could generate a stray T-storm or two...but the 
chance of this happening appears low due to low boundary layer 
moisture. 


By Friday...W-nwly mean layer flow turns southwesterly with amplification of the 
upper ridge over the western Great Plains. This opens the door to a long 
fetch of subtropical/monsoonal moisture which models show extending 
as far south as the Pacific coast of Mexico. Models also show a 
shortwave trough traveling newrd within this moisture plume up over 
the 4-corners region Friday evening and over N-cntrl/northestern Colorado on Sat. 
Should this pattern materialize as indicated...could see shower/T- 
storm chances increasing from SW-to-NE across the forecast area Friday 
night and Sat as well as a return to temperatures slightly below average 
due to a steady increase in cloud cover. 


&& 


Aviation...(for the tafs through 18z Tuesday morning) 
issued at 1034 am MDT Monday Aug 3 2015 


Current trends in the tafs seem reasonable at this time with 
increasing threat of showers and thunderstorms as the day wears 
on. Predicted gusty southeasterlies also seem OK for this 
afternoon. Latest high resolution models are suggesting another 
band of showers crossing the Front Range urban areas around middle 
evening so may considering keeping a thunderstorm threat longer in 
the new issuance. 


&& 


Bou watches/warnings/advisories...none. 


&& 


$$ 


Update...et 
short term...entrekin 
long term...Baker 
aviation...et 



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