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Area forecast discussion 
National Weather Service Denver/Boulder Colorado
852 PM MDT Friday Jul 3 2015

issued at 834 PM MDT Friday Jul 3 2015

Pretty quiet evening thus far. Earlier activity over South Park
and the mountainous areas generally south of Interstate 70 has
settled down. There was one other severe storm that clipped
northeast Larimer County as well. Radar continues to show some
boundaries running around which may be able get something going
although cin is increasing nicely at this time. Rap analyses
showed some pretty hefty qg subsidence over the area this
afternoon which may have helped squelch most of the convection
in spite of the high cape values.

Saturday is anticipated to have less subsidence...less vertical
wind shear and in general less cape. The upper foothills and far
northeast plains are predicted to have the most cape with the
urban corridor the most stable.


Short term...(this evening through saturday)
issued at 349 PM MDT Friday Jul 3 2015

Upper level ridge of high pressure remains centered over
southwestern Utah...with a moderate northwest flow aloft over
Colorado. At 14z...the RUC showed a 60+kt jet maximum over eastern
Wyoming. The surface gradient between high pressure over the Great
Plains and low pressure over Utah will produce light east to
southeast winds across the plains this afternoon and evening.
Dewpoints on the plains at 15z ranged from the middle 50s to the low
60s. The GFS and RUC show some drier air mixing down by 00z with
dewpoints dropping into the 40s in Denver...while the NAM keeps the
dewpoints in the upper 50s. I think the NAM is too high and the GFS
and RUC are too low. Therefore...I will take a compromise between
the models with dewpoints in the low 50s. The GFS...NAM and all of
the high resolution models showing scattered showers and
thunderstorms over the mountains and higher foothills later this
afternoon...with isolated activity over the plains. The activity
seems to shift into mountains south of I-70...southern foothills and
Palmer Divide this evening. There is enough shear and moisture
around combined with the upper level jet to produce one or two
severe storms east of The Divide this afternoon and evening. Storm Prediction Center has
a slight risk of severe storms across Lincoln and eastern Elbert
counties...with a marginal risk across much of the remainder of the
County Warning Area. With precipitable waters around an inch...we could also see locally heavy
rainfall. However...the storms should have good movement which
should keep the flash flooding threat low.

On Saturday...the upper low shifts into southern New Mexico...with a
more westerly flow aloft over Colorado. All the models show 700 mb
temperatures on Saturday 3 to 4 degrees warmer...therefore the
Fourth of July looks to be hot with temperatures in the 90s.
Isolated to scattered thunderstorms still look possible most
numerous from Park County eastward across the southern foothills
and Palmer Divide.

Long term...(saturday night through friday)
issued at 349 PM MDT Friday Jul 3 2015

Warmer and drier air will move over Colorado Sunday bringing
warmer temperatures. Still enough low level moisture for diurnally
driven storms. A cold front will move through in the late
afternoon and evening that will likely focus the storm activity.
Cooler and still moist air will move in behind the front...while
an area of lift associated with an upper level trough also moves
through overnight. This could keep showers and a few storms going
through the night.

For Monday low levels will be capped much of the day under the
cooler air and likely cloud cover. Main threat of storms will be
in the mountains...though still some chance on the plains late in
the day. Storms could be slower moving on this day with lighter
winds aloft and upslope...interface between the low level air and
the warmer mountain air...the east slopes of the Front Range...would
be the likely trouble spot but the low level air will probably be
too cool to create strong storms. Tuesday will be a similar
situation but less of all of that as the airmass starts to warm
and dry a bit and there will be a bit more flow aloft.

The end of the week looks warmer and drier again. Some
discrepancies on the strength and position of ridging downstream
from a West Coast trough...but general agreement on a dry west-southwest
flow. There could be a Sweet spot where it is warm enough but
still moist enough for an active day...most likely Wednesday.
Still some threat of storms after that with some low level
moisture but the warmth aloft will likely cap it...will go for a
pretty Low Key convective forecast on Thursday and Friday.


Aviation...(for the tafs through 06z Saturday evening)
issued at 834 PM MDT Friday Jul 3 2015

South to southeast winds will impact kapa and kden with kbjc
starting to transition to drainage. Kapa and kden should begin
their nocturnal winds by around 06z. Still a small threat of
convection yet this evening. Saturday will be similar to Friday
with some afternoon convection and relatively normal diurnal


issued at 349 PM MDT Friday Jul 3 2015

Isolated to scattered storms will be possible later this afternoon
and evening...most numerous over the mountains...southern
foothills and Palmer Divide. Some of the storms may produce
locally heavy rain. The storms will be moving at a pretty good
clip...therefore the flash flood threat will remain low.


Bou watches/warnings/advisories...

short term...jk
long term...gimmestad

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