Weather

635 
fxus65 kgjt 272042 
afdgjt 


Area forecast discussion 
National Weather Service Grand Junction Colorado 
240 PM MDT Wednesday Aug 27 2008 


Short term...tonight through Friday... 
a weak upper level wave has been sagging south across the southern 
half of the forecast area. Afternoon and early evening convection 
will be limited from the Abajo and San Juan Mountains and areas 
south. Stable and drier air mass that resides over the northern half 
follows upper level wave this evening. Convection over San Juan 
County Utah and extreme southwestern Colorado should diminish quickly this 
evening...but a few storms may be stubborn and persist beyond sunset 
given the higher precipitable water content south of the southern 
mountains. By midnight...all storms should have ended as upper 
level wave will have cleared the forecast area. Across the northern 
half...a thin cirrus shield moves across area but the back edge of 
the cirrus has reached northwest Utah. Cirrus shield should not impact 
sensible weather and will keep the sky grids mostly clear. 


Dry west to northwest flow prevails on Thursday and continues into 
Friday. Convective potential will be non existant on Thursday for 
the entire forecast area (although small flat afternoon cumuli will 
form over the southern mountains.) But light southerly flow returns to 
the far south on Friday and this will raise precipitable water and 
increase potential instability. After a day of rest...isolated 
storms will form over the San Juan Mountains and the south facing 
foothills. The northern two thirds of the forecast area will stay dry. 
Afternoon maximums will be steady for the next two days...but a 
notch cooler at night given lower relative humidity and greater 
diurnal temperature swings. 


Long term...Friday night through Wednesday...high pressure will 
shift eastward Saturday as a strong Pacific weather system deepens 
over the northwest coast. This will produce a south-southeast flow over our County Warning Area which 
will bring deep layer moisture into the region...meanwhile Pacific 
dynamics become available to act on the moisture as the trough sinks 
into the Great Basin Sunday. Expect to see widespread locally heavy 
precipitation Sunday/early Monday. Temperatures will be be correspondingly lower 
with frontal passage occurring late Monday. Tuesday conditions dry 
with westerly flow giving way to a southwesterly flow Wednesday as 
the next trough moves through the northern rockies. 


&& 


Aviation... 
isolated thunderstorms will last until 03z this evening...south of a 
line from Monticello in southeast Utah to Gunnison. Thunderstorm 
outflows will cause brief gusty winds...most notably at kcez and 
kdro. Otherwise VFR conditions persists through Thursday. 




&& 


Gjt watches/warnings/advisories... 
Colorado...none. 
Utah...none. 


$$ 


Short term.....Pf 
long term......mc 
aviation.......pf