Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

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

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 12z Tuesday morning)
issued at 310 am MDT Monday Aug 3 2015

An upper level wave and higher moisture levels spells higher
chances for showers and thunderstorms with best chances from 21z-
02z and then diminishing later in the evening. Expect heavy rain
and gusty winds with the showers. With passing showers could
result in ils approaches for a short time. Surface winds will
shift southeast and become gusty this afternoon as the surface
trough intensifies.

&&

Bou watches/warnings/advisories...
none.
&&

$$

Short term...entrekin
long term...Baker
aviation...entrekin

National Weather Service Glossary of Abbreviations