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Area forecast discussion 
National Weather Service Denver/Boulder Colorado
958 am MDT Wednesday Jul 29 2015

issued at 958 am MDT Wednesday Jul 29 2015

Scattered rain showers have developed over Lincoln County on the
northern fringe of the monsoonal moisture moving over the state
out of New Mexico. The hrrr model moves these showers off to the
east over the next couple hours with dry weather then continuing
through the afternoon across the forecast area. The latest run of
the NAM also shows the forecast area remaining dry this aftenroon
and evening after the the Lincoln County showers dissipate.
Current forecast for this afternoon shows low probability of precipitation over Park
County and the Palmer Divide...which will remain unchanged to
account for the presence of moisture to our south.

Adding a couple hours of scattered showers to the Palmer Divide
this morning will be the only change to the forecasts at this


Short term...(today through tonight)
issued at 349 am MDT Wednesday Jul 29 2015

A west-southwest flow aloft will prevail as an upper level ridge
remains over the Southern Plains. A few showers have formed this
morning over Lincoln County and are expected to move east of the
area. Monsoon moisture will remain over the state...with the
greatest moisture being over the southeast Colorado. Precipitable
water values will be three-quarters of an inch to one inch.
However...airmass will be stable over the plains and slightly
unstable along the Front Range and over the higher terrain where
convective available potential energy will be less than 500 j/kg. Best chance for a shower or storm
will be south and over the higher terrain this afternoon and

Surface high will move from the northern rockies to Central Plains.
This will produce southeast winds to with gusts this afternoon up to
25 miles per hour. Highs today will be similar to yesterday's readings with
highs in the 80s over northeast Colorado.

Long term...(thursday through tuesday)
issued at 349 am MDT Wednesday Jul 29 2015

On Thursday...a broad upper level ridge will stretch from Southern
California to the southeastern Gulf states and along its northern periphery
60-80kt middle-level zonal flow. Beneath the western sector of this ridge
will be a plume of subtropical moisture which models show nudging
northward over southern Colorado. From there they show the main core of
this moisture being sheared eastward away from northestern Colorado and the
Front Range. However late on Thursday...models also show southeasterly surface-
700mb on the plains of Colorado driving a low-level moisture/Theta-E
ridge up into northestern Colorado. By Thursday evening...NAM indicates 750-
1000 j/kg of surface based cape across Douglas...Elbert and Lincoln
counties. GFS and European model (ecmwf) convective available potential energy are spread out across the plains with
the higher values approaching a 1000 j/kgs across the southeastern corner of
the County Warning Area. If it were not for the warm temperatures aloft and strong cap
up around 550 mbs...eastern sections of the forecast area could end up
seeing more than just a few low top T-storms producing no more than
a rain shower and gusty winds. That said...have slightly raised
precipitation chances over the Front Range and along the Palmer Divide out
across Lincoln County Thursday afternoon and evening. Areas roughly
north of Denver should escape any precipitation or storms as this air
appears drier and too capped. Highs on Thursday only slightly warmer
than Wednesday and slight a 1-2degs c below average for the date.

For Friday...the upper ridge is forecast to build northwestward up
over the Great Basin placing northestern Colorado more under northwesterly flow
aloft. This leads to drying aloft but not much in the way of
cooling. This amplification on the ridge allows for some subtropical
moisture pooling over New Mexico/eastern Arizona to flow northward along
The Spine of the Colorado rockies. Precipitable water charts show high country
values creeping up through the day with the NAM and GFS indicating
pockets of light quantitative precipitation forecast over and near the Front Range by afternoon.
However the ec and sref show the bulk of this light precipitation farther
out on the plains in proximity of greater low-level moisture...
elevated cape and shear values. For now will hold onto 20-30pct probability of precipitation
over the high terrain...and 10-20pct probability of precipitation mainly over the Palmer
Divide and adjacent plains through evening on Friday.

Looking ahead to the period Saturday-Wednesday...the upper ridge
continues to bulge northwestward towards the Pacific northwest over
the weekend...placing the forecast area under a drier and more stable
northwesterly middle-level flow. Therefore should see less storm
activity on Saturday...with the better chance of T-storms with
steeper lapse rates over the higher terrain. On Sunday...models show
the upper ridge shifting east with light west-northwesterly flow over the County Warning Area.
Subtropical moisture trapped beneath the ridge coupled with strong
daytime heating may result in a bit more T-storm coverage in the
high country. So raised probability of precipitation slightly up there. Do not see much
convective activity on the plains. Highs on Saturday and Sunday
continue to creep up with reading returning to near to slightly
above average. Monday through Wednesday...the upper ridge is prognosticated
to remain over the Rocky Mountain region with little day-to-day change in
weather. Expect near average temperatures and a slight chance of afternoon
and evening T-storms mountains and plains each day.


Aviation...(for the tafs through 18z Thursday morning)
issued at 958 am MDT Wednesday Jul 29 2015

Managing wind shifts at the Airport through this afternoon will be
the only forecast problem of the day today. Southeasterly flow
across the plains is forecast to persist through the afternoon
which will produce south to southeasterly winds at kden through
this evening. The transistion back to nocturnal southerlies should
then occur between 02z and 04z. No other aviation impacts today.


Bou watches/warnings/advisories...


short term...meier
long term...Baker

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