Area forecast discussion
National Weather Service Grand Junction Colorado
339 PM MDT Tuesday may 21 2013
Short term...(this evening through Wednesday night)
issued at 233 PM MDT Tuesday may 21 2013
Considerable amount of low top cumuli have formed over the higher
terrain...but appears that warming and subsidence aloft have reduced
convective potential. Still have a couple more hours before
maximum surface heating...so would not be surprised if few showers
develop with an isolated lightning strike. The best threat will be
over the south facing San Juan Mountains and the Uinta Mountains.
Convection is diurnally driven and any convective activity will end
around sunset.
High clouds associated with a sheared speed maxima from the eastern
Pacific have reached the Utah spine. These clouds will spread
across western Colorado tonight and may limit nocturnal cooling.
Otherwise no sensible weather is expected for tonight.
By daybreak...high clouds will have moved downstream. Southwest
gradient flow strengthens on Wednesday as Colorado will be
squeezed between the strong Pacific northwest closed low and
downstream ridge. Drier air gets advected from Arizona...but some
convective potential still exists near the park/Gore ranges.
Wednesday night will be mild and nocturnal drainage winds will be
stronger given the thermally driven surface trough that cuts
across Utah.
Long term...(thursday through tuesday)
issued at 233 PM MDT Tuesday may 21 2013
Southwesterly winds associated with upper level ridge
will increase Thursday afternoon as the upper level low over the
Pacific northwest continues to interact with the ridge in place.
Higher winds are expected to mix down to the surface during the
afternoon Thursday. These winds are expected to subside overnight
Thursday but are once again expected to increase with daytime
heating Friday. Overall into the weekend...conditions will remain
dry...warm...and windy. See details below for fire weather
concerns.
Early next week...the upper level ridge in place weakens slightly
and winds will shift to westerly...allowing temperatures to
cool by a few degrees. Temperatures are still expected to be
near 80 degrees (near normal) early next week and at this
time...there is very little threat of precipitation through
Tuesday.
&&
Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 233 PM MDT Tuesday may 21 2013
VFR will continue at all taf sites and airfields through the next 24
hours. Isolated mountain -shra/-tsra will be possible through 02z
this evening. After 18z Wednesday...isolated -shra/-tsra will be
limited to near the Continental Divide.
&&
Fire weather...
issued at 218 am MDT Tuesday may 21 2013
Wednesday...winds are expected to pick up in the afternoon but
not quite reach critical fire weather criteria. Localized gusts to 25
miles per hour are expected to occur with relative humidity 15% or lower...but should not
last for 3 hours or more.
Red flag warnings are in effect for Thursday between noon and 9pm. Gusty
winds...low relative humidity and dry fuels over the lower
elevations of zones 203...207...290...292...and 293 will create
critical fire weather concerns. Winds are expected to subside
overnight...but may pick up again Friday and into the weekend.
&&
Gjt watches/warnings/advisories...
Colorado...red flag warning from noon to 9 PM MDT Thursday for coz203-207-
290-292-293.
Utah...none.
&&
$$
Short term...pf
long term...jam
aviation...pf
fire weather...jam
