Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Denver/Boulder Colorado
759 PM MDT Friday Jul 11 2014

Update...
issued at 753 PM MDT Friday Jul 11 2014

Good coverage of showers and thunderstorms wasm moving across the far northestern
plains early this evening and will continue through 10 PM and then
decrease. Along the Front Range activity has generally ended.
However a band of showers and storms moving into the mountains may
cross the area between 10 PM and midnight if they hold together.



&&

Short term...(this evening through saturday)
issued at 316 PM MDT Friday Jul 11 2014

Showers and thunderstorms will continue to form and spread east
across the area through early to middle evening. With precipitable
water values near 1.25 inches...heavy rain will accompany many of
the storms. Convective available potential energy of 1000 to 1500 j/kg may produce a few severe
storms even though shear is marginal...mainly over northeast
Colorado. Storms are moving east-northeast roughly at 10 to 20
miles per hour...thus keeping the flash flooding threat isolated.

Surface low pressure over southeast Colorado and outflow from the
exiting storms will produce another surge from the north that will
keep the airmass moist overnight. Could see some low clouds towards
sunrise...especially over the northeast corner of the state. This
surge will also lead to cooler high temperatures on Saturday.

Airmass will remain moist Saturday with precipitable water values of
one inch to 1.25 over northeast Colorado. Appears another weak
disturbance in the flow aloft will help trigger thunderstorms
Saturday afternoon. The best chance for storms will be over the
mountains and along the Front Range. Increased probability of precipitation to likely for
this. Because of the moist airmass...heavy rainfall will be a threat
again. However...westerly winds aloft of 15 to 25 knots will keep
storms moving along and keep the flash flood threat low. Convective available potential energy will
generally be less than 1000 j/kg and shear will be just OK. Could
see a couple of storms that just meet severe threshold during the
afternoon.

Long term...(saturday night through friday)
issued at 316 PM MDT Friday Jul 11 2014

Storms to continue across much of the area Saturday evening...best
chance along the foothills and across the Palmer Divide. Precipitable
water values over an inch across the plains...so threat for heavy
rain producing storms continues. Still a concern for flash flooding
though it appears there will enough storm motion to keep the storms
moving and limit this threat. Cape values of around 1000 j/kg prognosticated
along the Palmer Divide into Lincoln County with a bit of directional
shear. Cannot rule out a severe storm or two in this region. By
midnight...most of the activity should be east of the area although
some storms could linger overnight. On Sunday...flow aloft becomes
northwest with upper ridge over the Great Basin. Airmass slightly
drier but precipitable water values still around an inch near the
foothills and close to 1.25 inches eastern plains. Cape values look
to be around 1000 j/kg along the urban corridor with roughly 800
j/kg further east. Still a decent chance for thunderstorms during
the afternoon and evening most areas. Despite the slightly drier
airmass...potential still exists for storms to produce locally
heavy rain. With a bit better shear...there is a slightly better
risk for a few severe thunderstorms producing large hail and
damaging wet microburst winds. Airmass still fairly cool with
highs in the middle 80s across the plains. For Monday... northwest
flow aloft to continue across Colorado with broad upper trough
over the Great Lakes region and upper ridge across Great Basin.
Models show middle level shortwave clipping the northeast corner of
Colorado with a surface front pushing across the northeast plains
during the afternoon. Airmass only slightly unstable behind front
with the best chance for afternoon and evening thunderstorms still
in and near the foothills and across the Palmer Divide. Little
change in temperatures expected with highs in the middle 80s across
northeast Colorado. For Tuesday...fairly strong northwest flow
aloft over Colorado with cooler airmass across northeast plains.
Airmass still fairly moist though slightly more stable across the
plains with the cooler low levels. Best chance for storms to be
across the higher terrain. Highs across northeast Colorado look to
be in middle and upper 70s.

For the later days Wednesday through Friday...northwest flow aloft
continues Wednesday with hints of a middle level shortwave during the
afternoon or evening. Airmass still moist with better instability
for some chance of mainly afternoon and evening thunderstorms.
Lift from the wave may increase the storm chances across the
plains. For Thursday and Friday...models show wave moving
southeast of the area. GFS quickly builds upper ridge across
western Colorado Thursday and moves it over Colorado Friday...
while the European model (ecmwf) shows the upper ridge over the Great Basin with
northwest flow aloft through Friday. Will continue the trend of
less thunderstorm chances with the increased subsidence under
weakening and drier northwest flow aloft. Temperatures to also
warm slightly as well.

&&

Aviation...(for the tafs through 06z Saturday evening)
issued at 753 PM MDT Friday Jul 11 2014

Although activity has ended there is a chance of showers and a few
thunderstorms moving across between 10 PM and midnight. After midnight
precipitation threat should end. Winds had become light north-northwest and may remain
so overnight. A weak fnt may affect the area around 15z with
winds becoming northeasterly. Current taf has no mention of low clouds
however but may have to keep an eye on this towards sunrise.

&&

Hydrology...
issued at 316 PM MDT Friday Jul 11 2014

Airmass to remain moist today and Saturday. There is a threat for
flash flooding...but due to storms moving at 10 to 20 miles per hour the
threat is low. Flood prone areas like burn areas will see the best
chance of flooding today and Saturday. The heaviest rainfall rates
will be around one inch in 20 minutes...though most areas will be
less.

Airmass only slightly drier Sunday but still fairly moist with a
chance for thunderstorms. Brief heavy rain a possibility... but storm
motion of around 15 miles per hour should keep the flooding threat low.

&&

Bou watches/warnings/advisories...
none.
&&

$$

Update...rpk
short term...meier
long term...d-l
aviation...rpk
hydrology...meier

National Weather Service Glossary of Abbreviations