588 
fxus65 kbou 072117 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
310 PM MDT Thursday Aug 7 2008 


Short term...acars soundings at kden have been showing a warm layer 
around 550 mb through the afternoon. This middle level warm pool has 
been keeping shower activity capped thus far. VAD wind profile and 
WSR-88D velocity shows deep easterly flow across the plains and 
reflectivity shows a few small showers moving across Washington and 
eastern Morgan counties. As the late afternoon progresses...outflow 
from the weak convection should continue piling low level moisture 
up against the foothills. At some point the cap may be broken and 
additional shower activity will have the potential to be slow moving 
and efficient at precipitation production. GPS-based precipitable 
water values in Boulder are around 1.3 inches...as was forecast by 
model soundings earlier today. Model soundings are showing warm 
cloud layers between 9000 and 10000 feet deep along with storm 
motions around 3 or 4 kts. Will let the Flash Flood Watch continue 
through 10 PM. The one thing that is missing from tonight's set up 
is any dynamic forcing. Will have to wait and see if outflow 
boundaries are enough to organize the convective activity. 


Later tonight...shower activity should end and moist low levels 
should allow patchy fog and stratus to form across the plains. 


Friday looks like moisture will linger while a weak short wave 
trough rotates over northern Colorado from its present position over 
Utah. The combination of dynamics...moisture and daytime heating 
should be enough to set up a third consecutive afternoon of active 
showers. Heavy rainfalls will again be a problem that needs 
monitoring. For now will stick with strong scattered probability of precipitation. Have 
gone close to MOS guidance for Friday afternoon temperatures. 
However...if the airmass remains as moist as it is this afternoon... 
it may be difficult to crack the 80 degree barrier. 


Long term...looks like another active evening Friday as a weak 
short wave currently moving northward through Utah is expected to 
overtop the ridge and slide east/southeast across eastern Colorado. 
Plenty of moisture is around again with precipitable water values of 
1.25 to 1.5 inches across the plains. Storm motion will be quite 
slow as well so we will have potential for more flash flooding. 
Will increase probability of precipitation further considering the above mentioned 
factors...and cant rule out some showers/storms lingering past 
midnight especially over the eastern plains. We may very well need 
another Flash Flood Watch for the foothills and plains...but will 
have to ride through tonights watch first. 


By Saturday...airmass should begin to dry as flow aloft begins to 
strengthen and turn northwesterly. This will result in less storm 
coverage and also reduce the heavy rainfall threat. Going forecast 
has this well handled. Little change expected for Sunday...although 
some of the medium range models are hinting at a weak short wave 
moving across the northern rockies which could help convective 
coverage. 


Looks like a more typical summertime forecast shaping up for Monday 
through Thursday of next week. High temperatures should rebound to around 
90f on the plains most days...while convective coverage will also be 
more isolated. 


&& 


Aviation...scattered evening thunderstorms are still expected 
around kden during the late afternoon and evening. Airmass is quite 
moist but not yet unstable. Continuing easterly flow across the 
plains coupled with boundaries from weak showers on the plains 
should be able to initiate additional showers over the urban 
corridor during the evening hours. Showers will probably be slow 
moving and capable of producing heavy rainfall. Ceilings and visibilities in 
MVFR category should be expected with showers through the evening. 
Freezing levels are quite high...so threat of hail is minimal. 


&& 


Bou watches/warnings/advisories...Flash Flood Watch until 10 PM MDT 
for the Front Range foothills...urban corridor...and western 
Palmer Divide...zones 35..36..38..39..40..41 and 43. 


&& 


$$ 


Kdrby/barjenbruch