Area forecast discussion
National Weather Service Denver/Boulder Colorado
815 PM MDT Wednesday may 22 2013
Update...
&&
Short term...a weak disturbance was moving across and was combining
with increasing upslope flow to generate some scattered showers and a
few thunderstorms along the fnt range. Appears most of this activity will
gradually end in the next few hours.
Aviation...gusty east-northeast winds behind frontal boundary should decrease in
the next hour or so. Weak convection was moving across the Airport
but should end by 03z. There is a boundary with south-southwest winds approaching
dia however last few radar scans have shown this boundary weakening
so for now will keep winds mainly Ely overnight. Should see some
stratus develop after 11z lingering through the late morning hours on
Thursday.
&&
Hydrology...no issues.
&&
Previous discussion... /issued 313 PM MDT Wednesday may 22 2013/
Short term...Colorado under weak high pressure aloft while at the
surface building high pressure over the Central Plains is
tightening the gradient with developing easterly low level flow
over the northeast plains. A weak Denver cyclone also trying to
develop as well this afternoon. 88d showing weak echoes beginning
to develop over higher east slopes with some moisture convergence
due to the easterly low level flow. Expect most of the showers to
be high based with gusty winds with only light rainfall. The
increasing easterly flow will push low level moisture into
northeast Colorado later tonight with stratus/fog over the plains.
Cooler temperatures expected on Thursday with readings only in the
60s across the plains. Forecast soundings showing strong low
level inversions over the plains with stable airmass in place and
no thunderstorms expected. Main change to the forecast was to
remove thunderstorms over the plains on Thursday afternoon. The
only thunderstorms will be over mountains and elevated terrain
above the inversions. Even showers in the mountains will be light
given lack of any significant moisture.
Long term...mountain showers and thunderstorms will be
diminishing through Thursday evening with another night of stratus
and patchy fog over the plains. Towards the eastern state
border...enough low level moisture is expected for some areas of
drizzle to occur. Southwest flow aloft will be increasing as the
upper ridge moves further out over the Great Plains. A Theta-E
ridge will be moving up from the south overnight and into Friday
along the eastern Colorado plains. A surface trough will be deepening
along the eastern plains as well to erode any remaining inversion.
Temperatures are expected to warm into the 80s over the plains and
into the 60s in the high country. Over the eastern plains...this
surge of moisture with surface heating will mix with convective available potential energy of
1400-1800 j/kg and bulk shear values near 40 kts to allow for
thunderstorms to develop...mainly along and east of a line from
Cheyenne, Wyoming to Limon. Areas toward the eastern state line may see
stronger storms. In terms of fire weather...the increased
southwest flow aloft will be bringing in drier and warmer air that
will produce humidities in the middle to upper teens and winds
gusting in the 20-30 miles per hour. However fuels are listed as still being
affected by the late season precipitation.
These thunderstorms over the eastern plains will likely last into
the evening before diminishing. Saturday and into the Holiday
weekend will have little change day to day as southwest flow
remains aloft and expecting little change to daily temperatures.
There will be isolated showers and thunderstorms each afternoon
and evening over the far eastern plains each day with a slight
chance over the high country on Sunday and Monday. Tuesday may see
more shower activity statewide as the upper ridge over the central
states breaks down a bit and an upper trough over the West Coast
slides east over the area.
Aviation...isolated high based showers/ts from 22-03z over the
area with gusty erratic winds expected. Still overall areal
coverage small so no mention of ts in taf's for now. Stratus will
develop later tonight but unclear how solid the deck will become
over terminal sites. Expect more scattered clouds at apa with
lesser chances of MVFR conditions. WRF simulated imagery showing
hole in the stratus cover over Denver due to the persistent
southeast winds at den/apa. No storms expected on Thursday with
stable airmass in place all day.
Hydrology...only light rain showers with storms over the higher
terrain this afternoon and again later Thursday afternoon with
amounts under a tenth of an inch. No flooding issues expected
while no significant snowmelt is occurring at this time.
&&
Bou watches/warnings/advisories...
none.
&&
$$
Short term...rpk
long term....dankers
aviation...rpk
