Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Denver/Boulder Colorado
422 am MDT Friday Sep 4 2015

Short term...(today through tonight )
issued at 422 am MDT Friday Sep 4 2015

Another round of showers for the mountain areas today while the
plains may remain dry through the afternoon and evening.
Subtropical moisture will continue streaming over the state from
the south today as a strong upper ridge remains over the
southeastern U.S. And a deep early season trough evolves over the
Pacific northwest. Moisture amounts over the mountains will be
comparable to the past few days but a possible connection to
Tropical Storm Kevin is going to need to be monitored. Deeper
moisture from Kevin appears like it will not arrive over Colorado
until tomorrow. In the meantime...the forecast for the mountains
will have showers and thunderstorms likely this afternoon and
early evening. On the plains...the GFS and European model (ecmwf) keep things dry
while the NAM brings a band of showers out across the plains. Will
stick with a 10-20 percent chance of showers in case the NAM is
right. Low level flow will remain southerly through the afternoon
while winds further aloft are more south-southwest than they have
been the past couple days. This flow pattern may make it hard for
many showers to begin tracking easterly and out over the plains.

The nearly meridional flow pattern may lead to some training
showers over the high country...but this will not become a problem
until moisture from T.S. Kevin arrives. Other than that...
temperatures should be about what they were yesterday...a few
degrees warmer than normal.

Long term...(saturday through thursday)
issued at 422 am MDT Friday Sep 4 2015

Southwesterly flow aloft will continue over the County Warning Area Saturday
through Sunday...with speeds on the increase. The flow becomes
west-southwesterly Sunday night as an upper trough to the west
nears Colorado and weakens. The jet level wind speeds are around
80 knots over the County Warning Area Saturday night through Sunday night. There
is weak upward synoptic scale energy on the qg vertical velocity
fields for the County Warning Area Saturday into Saturday evening...then all
downward energy through Sunday evening. There is decent energy
with the upper trough but it is all north of Colorado. The
boundary layer winds have some downsloping to them for Saturday
..then normal drainage Saturday night. A slightly cooler airmass
with some weak upslope is prognosticated on Sunday...then weak drainage
Sunday night. For moisture...there is quite a bit on Saturday into
Saturday evening...then it dries out pretty good early Sunday
morning through Monday morning. There are still some precipitable
water values above one inch over the plains Saturday into Saturday
evening...then they decreases into the 0.25 to 0.75 inch range by
late day Sunday. There is a bit of cape around late day Saturday
..but nothing in the subsidence by late day Sunday. There is some
measurable rainfall on the quantitative precipitation forecast fields late day Saturday and then
nothing for late day Sunday. So for probability of precipitation will go with 10-40%s for
late day Saturday...then nothing Sunday and Sunday night. For
temperatures...saturday's highs are 0-15. C warmer than today's
expected highs. For the later days...Monday through Thursday...
models keep pretty strong west-southwesterly flow aloft over the
County Warning Area Monday and Tuesday...then weaker zonal flow Wednesday and
Thursday. There is a cold front to move in on Tuesday. Moisture is
not very good through the period...with the best on Tuesday and
Tuesday evening. Temperatures look to be a bit above seasonal


Aviation...(for the tafs through 12z Saturday morning)
issued at 422 am MDT Friday Sep 4 2015

Mostly clear skies this morning with light southerly winds. No
aviation impacts expected until later this afternoon when showers
and thunderstorms develop over the mountains. A few showers may
also spread over the Denver metropolitan area...but less activity than
yesterday afternoon is expected. Flow aloft is going to be out of
the south-southwest...which will decrease the tendency for storms
to develop the eastward push necessary to begin moving onto the
plains. Kbjc and kapa will have slightly better chances for
showers than out at kden. Tafs will stick with the mention of vcsh
since the chances of a thunderstorm moving across any of the
airports is only about 10 percent. Skies will clear out again
later this evening...after any showers move across the Denver area
in the late afternoon and early evening.


Bou watches/warnings/advisories...


Short term...dankers
long term...rjk

National Weather Service Glossary of Abbreviations