Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Denver/Boulder Colorado
1110 am MDT Monday Mar 17 2014
Short term...winds beginning increase across the area ahead of
the approaching trough. Also surface low and Lee trough starting
to intensify across the plains. Latest models still indicating
potential gusts to 50 miles per hour across the plains. Not much of a
mountain wave at this time...so don't think winds will reach high
wind criteria. Gusts to 65 miles per hour still possible along the foothills.
Moisture will continue to increase across the mountains during the
afternoon along with middle level qg ascent. Orographics improve by
evening along with decent lapse rates which continue overnight as
upper trough moves into Colorado. Current Winter Weather Advisory
for zones 31 and 33 still look on track. Some chance for
precipitation across the plains overnight with increasing middle
level ascent. However...strong downslope flow will limit the
precipitation chances along the urban corridor. Current probability of precipitation and
weather look good for now. There is also some potential for high
winds late tonight and Tuesday morning if the 50 kts of boundary
layer winds mixes to the surface. At this time will hold onto the
watch for the far northeast zones.
Aviation...mixing helping to increase southwest winds across the
area...although rotor along the foothills keeping a southeast wind
at kbjc. The rotor should be short lived as the mixing will
continue. Winds to become more westerly 19z...as shown by the
latest models and will adjust the tafs accordingly.
Otherwise...current taf trends look reasonable. Some gusts to 50
miles per hour possible between 21z and 01z. Winds to then become more
northwest during the evening and decrease. Some chance for rain
and snow showers after 06z...with the best chance northeast of the
Fire weather...winds to increase across the plains during the
afternoon with speeds between 35 and 50 miles per hour. Humidity readings
expected to drop into the single digits. Red flag warning to
continue for areas where the fuels are driest and most susceptible
to wildfire spread.
Previous discussion... /issued 408 am MDT Monday Mar 17 2014/
Short term...westerly flow aloft will increase ahead of a potent upper
level trough that will move across the area tonight. Meanwhile at
the surface low pressure will intensify from eastern Wyoming into eastern Colorado with strong
downslope low level flow by afternoon. Moisture will gradually increase
in the mountains by late afternoon into the evening hours with snow
developing especially north of I-70 which will continue overnight.
Favorable orographics and decent lapse rates should allow for
advisory amounts in zones 31 and 33 with lower amounts in zn 34. In
addition gusty winds will cause areas of blowing snow over the
Gusty winds will this morining over the higher terrain and then
spread across the plains by middle to late afternoon. Appears lack of a
mountain wave will keep wind speeds below high wind criteria in most
areas with gusts to 65 miles per hour in the mountains and foothills. Over the
plains will likely see some gusts from 40 to 50 miles per hour. High temperatures this
afternoon will range from the upper 60s to middle 70s over northestern Colorado.
For tonight as main upper level trough moves across northestern Colorado there
will be a chance of rain showers changing to snow over the northestern
plains after midnight. Strong downslope flow in and near the foothills
will lead to lower precipitation chances along the Front Range and Palmer
Divide. Meanwhile boundary layer winds are forecast to increase to 50-55 kts
after 06z over the plains and if showers occur this would allow for
stronger winds in the boundary layer to mix down to the surface allowing for
some potential for high winds late tonight into Tuesday morning.
Long term...models have an upper trough axis over eastern Colorado
at 12z Tuesday morning. By Tuesday afternoon...west-northwesterly
flow aloft is over the County Warning Area and it is supposed to continue Tuesday
night. Northwesterly flow aloft is prognosticated on Wednesday...becoming
west-northwesterly again Wednesday night. Fairly strong downward
qg vertical velocity is prognosticated over the forecast area Tuesday
well into Wednesday afternoon. After that...the synoptic scale
energy is benign into Thursday morning. Pretty strong north-
northwesterly boundary layer flow is prognosticated Tuesday...decreasing
Tuesday night. Weaker downsloping flow is prognosticated on Wednesday
.With normal drainage wind patterns expected Wednesday night.
For moisture...there is some over the mountains and the eastern
two-thirds of the plains on Tuesday. It dries out slowly Tuesday
night...Wednesday is pretty dry...with just some upper level
moisture for Wednesday night. The quantitative precipitation forecast fields have light amounts of
measurable precipitation over the mountains and eastern plains
Tuesday...with just a tad over the mountains Tuesday night. There
is nothing Wednesday or Wednesday night. So with the upper trough
looking a bit stronger and digging a bit further south will up
probability of precipitation a tad on the plains for Tuesday. Will keep "likely"s for the
most part over the mountains. Will linger some minor probability of precipitation over the
mountains on Tuesday evening...then dry through Wednesday night.
No highlights for snow amounts right now. Will go with a high wind
watch for the eastern plains Tuesday morning with the prognosticated
wind speeds in mind. Of note...if models continue the trend of a
stronger...more further south upper trough...the eastern plains
could see higher probability of precipitation and blizzard conditions with the strong
winds. Something to watch for. For temperatures...tuesday's highs
are 6-15 c colder than today's highs. Wednesday's readings are up
4-7 c from tuesday's. For the later days...Thursday through
Sunday...the flow aloft is basically zonal all four days. There
is quite a bit of moisture and some weak upward synoptic scale
energy for Saturday and Saturday night. Will go with some minor
probability of precipitation for all areas.
Aviation...south-southwest winds this morning will become more westerly by 18z and
then increase through the afternoon hours. Speeds of 15 to 25 miles per hour with
gusts to 35 miles per hour will occur between 18z and 21z and then increase
to 25 to 35 miles per hour with gusts to 50 miles per hour in the 21z-01z timeframe.
After 01z winds will become more west-northwest with speeds in the 20 to 30
miles per hour range which will continue through 06z. After 06z winds may
decrease to 10 to 20 miles per hour. With strong downslope flow along the Front
Range tonight best chance for rain and showers will stay to the NE of
the Airport overnight.
Fire weather...strong gusty winds between 35 and 50 miles per hour from the
southwest/west with single digit humidities will bring red flag
conditions to the northeast plains this afternoon afternoon and
evening. Red flag warning is where fuels are driest on the plains
and most susceptible to wildfire spread.
red flag warning until 8 PM MDT this evening for coz241-242-
High wind watch from late tonight through Tuesday morning for
Winter Weather Advisory from 6 PM this evening to 6 am MDT
Tuesday for coz031-033.