Area forecast discussion
National Weather Service Denver/Boulder Colorado
813 PM MDT Wednesday Jun 19 2013
Update...
&&
Short term...an isolated high based thunderstorm has recently developed
over northestern Weld County. Although airmass is rather capped over the
northestern plains could see an addititional storm or two through 06z.
Otherwise it will be dry.
Aviation...pesky Denver cyclone continues with main low over the
western suburbs which has allowed for gusty south-southeast winds at dia. Latest
rap moves this feature into northern Weld by midnight with south-southwest winds
developing by 06z. Overnight a cold front will move into the area
after 12z with winds becoming north-northeast by 14z.
&&
Previous discussion... /issued 329 PM MDT Wednesday Jun 19 2013/
Short term...low level moisture was scouring out from southwest
to northeast across the plains. Even where the better low level
moisture was hanging on...the airmass was moderately capped.
However...there is still potential to break through the cap where
best low level convergence occurs. This would be near intersection
of dryline pushing east to near Washington County and eastern edge
of Denver convergence zone in Morgan County. If storms develop...
they could become severe with sb convective available potential energy of 3000-4000 j/kg. There
will be dry air entrainment but even then mixed layer convective available potential energy would
be close to 2000 j/kg.
A weak but dry cool front will back across the plains during the
early morning hours Thursday with just a slight cooling of a
couple degrees. Temperatures will still be above normal...and
increasing winds during the afternoon will lead to more red flag
conditions over the high mountains valleys and Palmer Divide
area...see fire weather section below.
Long term...gusty winds will continue into the evening hours
across the area...in particular mountain valleys and Palmer
Divide...before decreasing by midnight. Humidity readings will
slowly increase as the airmass cools. Red flag warning mountain
valleys and Palmer Divide through 02z still seems reasonable. Dry
airmass with clear skies and light winds will allow temperatures
to drop into the 50s across the plains with mostly 40s mountains.
On Friday... southwest flow aloft continues. Models indicate a
slight weakening of the gradient by the afternoon which may lead
to a decrease in wind speeds. In addition there is some middle level
moisture prognosticated to move over the area that could limit mixing.
Airmass will remain fairly dry. Models show some increase in low
level moisture across the plains during the morning...then scour
out the moisture by the afternoon. Fire danger will remain
elevated with some increase in winds during the afternoon and the
potential for critical fire weather conditions...especially across
the mountain valleys. For now will hold off on any hoisting of
fire weather watches due to ongoing warnings. On Saturday...
southwest flow aloft to continue as models show upper trough
moving into Idaho and western Montana. Weak front prognosticated to move
into northeast plains with slight cooling and some increase in low
level moisture. Models also indicate some middle level qg ascent
over the area during the afternoon and evening...may be enough to
generate a few storms. For Sunday...flow aloft becomes a bit more
westerly as upper trough moves across Montana. Airmass slightly
drier though there may be enough moisture across the plains for a
slight chance of afternoon and evening thunderstorms. For the
later days Monday through Wednesday...models show upper ridge
building across the area with dry and warmer condition. There are
hints at a weak upper level wave moving Wyoming and Nebraska
Tuesday which could provide some lift. Airmass looks dry so will
not include storms at this time.
Aviation...gusty southerly winds at kden and kapa will slowly
decrease through 02z-04z with the loss of daytime heating. Still
a slight chance of winds switching to a more northerly/
northwesterly direction 23z-03z if Denver convergence zone shifts
back southward. Will continue to monitor. Otherwise look for weak
but dry front to switch winds to northeasterly 12z-15z Thursday.
Then diurnal but stronger than normal easterlies expected in the
Front Range airports for the remainder of Thursday. VFR conditions
with no chance of thunderstorms.
Fire weather...main concern through this period will be gusty
winds and very low humidities during the afternoon and early
evening hours. Will continue the red flag warning for the High
Mountain valleys this evening...and then upgrade the watch to a
red flag warning for Thursday afternoon/evening when winds
increase again. They will likely be just a little lighter than
today...but still strong enough with very low humidities to
provide red flag conditions in the High Mountain valleys...and
eventually Palmer Divide where fuels will exhibit further drying
after yesterdays rains. Fire danger will remain elevated through
Friday.
Hydrology...no concerns.
&&
Bou watches/warnings/advisories...
red flag warning from noon to 8 PM MDT Thursday for coz211-213-
214-241.
&&
$$
Short term...rpk
long term....d-l
aviation...rpk
