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Area forecast discussion 
National Weather Service Pueblo Colorado 
427 am MDT Sat Aug 30 2008 


Short term... 
(today and tonight) 


..main concern will be increasing monsoon moisture later tonight 
over the SW mountains... 


Currently...mesoscale convective system over far southeast Colorado continues to dissipate with an area 
of decreasing rainfall over Kiowa County at 3 am. A few showers/thunderstorms and rain 
were also noted over the SW mountains wat vap shows a large area of 
upper level moisture extending from Texas westward into the desert SW...and 
then northward across Nevada into Idaho. The moisture farther north into Idaho is 
being advected northward by an amplifying trough off the northwest Pacific coast. 


Today...Lee troughing to become better defined...especially in the 
lower levels as Pacific trough continues onshore. Simulations are 
relatively dry across the area next 24h...but this looks a bit 
underdone given wat vap imagery...and believe we will see a bit more 
precipitation...especially over the mountains...then the simulations indicate. 
As for temperatures...should see temperatures in the 85-90f range most plains 
areas with 70s and 80s mountains 


Tonight...all guidance shows relative humidity values through the column increasing 
late tonight across north nm and moving into far S Colorado. For this 
reason...kept isolated to scattered probability of precipitation across the c and SW mountains through 
the period. As for the plains...I expect less precipitation tonight then we saw 
last night. It should remain breezy across the plains...with low 
temperatures only reaching into the u50s/l60s. 


Long term... 
(saturday through thursday) 


..upper low still projected to glance by to the northwest bringing 
increasing winds and an upswing in thunderstorm chances for Sunday 
and Monday...with cooling projected for Tuesday and Wednesday behind 
the cold front... 


Models still in fairly good agreement with overall big picture. 
Upper trough digs into the Pacific northwest on Sunday...then moves 
across Idaho/northern Nevada/northern Utah on Monday...the lifts off to the NE across 
the northern US rockies. Models start to diverge with the details for 
Monday and beyond with GFS keeping trough more amplified and slower as it 
lifts it across Wyoming on Monday night. NAM and European model (ecmwf) are less amplified 
with a faster and slightly farther north track during this same time 
period. 


As for sensible weather...deep southerly flow will increase across 
the area on Sunday with gusty south winds developing across the southeast 
plains as Lee trough deepens in response to incoming system. This 
pulls moisture up from the south across the area with widespread 
convection expected across the western areas where both NAM/GFS indicate 
some shortwave energy lifts across the area ahead of the deepening 
trough. If sufficient low level moisture advects into western portions of 
the forecast area...then could see some strong to severe storms across the 
mountains/interior valleys...as deep layer shears increase...and middle 
level lapse rates steepen. Heavy rain with the potential for 
localized flash flooding will also be a concern out 
west...especially if thunderstorms initiate in favored SW flow 
upslope regions...then train across the same areas. Across the 
southeast plains...surface dew points will also be in the upper 40s to lower 
50s...however this area is still a good ways ahead of the 
system...so shears and middle level instability is not as great as 
across western areas. Main story for the east though will be the 
strong southerly winds. Could see some gradient winds of sustained 
20-30 miles per hour with gusts to 45 miles per hour...with deep mixing helping temperatures warm 
into the lower 90s. Have kept maxes on the warm side of guidance 
given this deep mixing potential. If fuels were considered critical...this 
could be a day worthy of fire weather highlights. However...given 
fuels are still moist from recent green up...and the fact that surface 
dew points will stay a bit too high...no highlights anticipated at 
this time. 


Sunday night should be fairly warm across the region as winds stay 
breezy/windy and cloud cover spreads across the eastern plains as 
well. Kept probability of precipitation going all night Sunday night...especially out west where 
best moisture and upper level forcing will coincide. Could even see 
some thunderstorms spreading up from the south across the eastern 
plains late Sun night/Monday morning with a band of isentropic 
lift. 


Monday...thunderstorm threat will spread eastward across the plains 
as trough glances by to the north and associated stronger wave of upward 
forcing moves across the area. Steeper lapse rates spread eastward 
across the plains during the afternoon...and combined with 
increasing deep layer shears...could see some severe thunderstorms 
along/east of the dry line as it sharpens up across the eastern 
plains. For now...NAM and GFS show potential for afternoon convective available potential energy a 
little over 1000 j/kg...with deeper moisture and better severe threat on 
the north side of the surface low (north of the area). Again...still 
some uncertainty on whether all these ingredients will come 
together. If track of the system is farther north...then threat may 
be more marginal as lapse rates aloft may not be as steep. 
Conceptually...damaging wind gusts will be possible west of the dry 
line...with potential for large hail and damaging winds east of the 
dry line if sufficient instability is present. Another windy day 
expected this day as well...though with cooling moving in 
aloft...this should keep maximum temperatures cooler and humidities slightly 
higher...which should limit threat for critical fire weather 
conditions in spite of the gusty winds. 


Front drops southward across the area for Monday night ushering in 
cooler temperatures for Tuesday. 00z runs look cooler with the air mass 
behind the front than runs from yesterday. 700 mb temperatures in the GFS are 
only +5 to +8c across the east Tuesday afternoon. This could mean maximum temperatures 
only in the 70s across the plains. Have cooled off maximum temperatures for 
both Tuesday and Wednesday...though might not be cool enough if models 
continue this trend. Tuesday night will be crisp...with some areas in 
the mountains dropping below freezing...and even some pockets of 
along the lower eastern slopes potentially seeing temperatures drop into 
the middle-upper 30s as air mass dries out within surface high. 


Zonal flow sets up over the area for Thursday with temperatures warming across 
the area as surface high shifts eastward and return southerly flow sets 
up. Long range models suggest next trough will send another cold 
front across the area Thursday night or Friday bringing another 
upswing in precipitation chances with more fall like temperatures. -Kt 


&& 


Aviation...VFR conditions expected through the next 24h. Only minor 
concerns will be isolated brief thunderstorms and rain...mainly kcos during the late 
afternoon time period. There is also a slight chance of some light ground 
fog kals this morning but given current T/dew point spreads...believe 
threat to low to mention. 




&& 


Pub watches/warnings/advisories... 
none. 
&& 


$$ 


34/31 

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