339 
fxus65 kbou 032050 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
250 PM MDT Friday Jul 3 2009 


Short term...short wave currently moving across central Colorado is 
enhancing showers and thunderstorms across the area. An extra 
extension of the short wave shown on satellite which was not 
captured by models is expected to continue this activity through the 
afternoon and evening. Dewpoints in the 50s and 60s will help with 
the instability. Moisture from the southwest continues to ride over 
the ridge to add to the available moisture...contributing to the 
precipitable water values over an inch this afternoon. Scattered 
showers and thunderstorms will continue moving off of the mountains 
and foothills onto the plains this evening. A thermal low over the 
Kansas and Colorado border will serve as a focus for low level 
convergence and with enough shear...a chance exists for some 
thunderstorms to reach severe criteria over the plains especially as 
the shortwave passes overhead late this afternoon. The shear will 
allow the storms to possibly produce heavy rain...large hail and 
strong gusty winds. A Severe Thunderstorm Watch will be in effect 
this late afternoon and evening for the far eastern plains as a 
result. A cold front on the back of the shortwave will slide south 
over northeastern Colorado keeping precipitation chances though 
midnight...even though good qg descent will be over the forecast 
area. Precipitation should end shortly after midnight though as the 
subsident airmass behind the cold front becomes dominant. 


Upslope flow after the cold front will keep dewpoints in the 50s and 
60s over the plains tomorrow. Moisture advected from the southwest 
will still be over the state as weak upper disturbances bring some 
weak qg ascent. Another round of scattered showers and 
thunderstorms are expected in the afternoon and evening. 
Temperatures will be a few degrees cooler tomorrow from the cold 
front...but still stay in the lower to middle 80s. 


Long term...more afternoon and evening showers and thunderstorms 
can be expected through Sunday. The atmosphere will remain rather 
unstable with daytime heating and embedded weak disturbances. One 
such disturbance is now seen over the northern California/Nevada 
border...and per the q-g vertical motion fields is shown to reach 
the forecast area Saturday night. This should help storm coverage 
Saturday evening...while supercell potential and severe weather 
threat on the plains will be supported by 0-6km bulk shear of 20-25 
M/S. 


On Sunday...both the NAM and GFS want to dry it out along the Front 
Range and shift the Theta-E axis eastward across the plains. There 
is some uncertainty with regard to this as high pressure over the 
Central Plains could promote stronger southeasterly flow and a 
Denver cyclone which would help the moisture hold in place across 
most of the Front Range. At this time...will have to broadbrush the 
area with scattered probability of precipitation given the uncertainty on the mesoscale 
features and amount of low level moisture. Again...there will be a 
threat of more severe storms with sufficient shear and instability. 


By Monday...the airmass should begin to stabilize and warm aloft as 
upper ridge begins to amplify just a bit. However...we are still in 
northwest flow aloft so low probability of precipitation are still justified...especially 
with low level moisture lurking over the plains. 


Tuesday through Friday will feature much drier and warmer southwest 
flow aloft. Temperatures are expected to push into the 90s for 
highs across the plains with 700 mb readings rising to around 20c. 
Any storms will be high based and produce mainly gusty winds and 
only light rainfall. Moisture will have a tendency to increase 
under the ridge so storm coverage may increase just slightly by the 
end of next week. 


&& 


Aviation...shower and thunderstorm coverage is expected to increase 
through 02z...with ceilings overall expected to remain above 6000 
feet. Winds will turn northerly around 03z as a cold front slides 
south over the forecast area. Airmass will dry out after 06z 
however. 


&& 


Bou watches/warnings/advisories...none. 


$$ 
Kriederman/barjenbruch