Weather

042 
fxus65 kpub 281031 
afdpub 


Area forecast discussion 
National Weather Service Pueblo Colorado 
431 am MDT Thursday Aug 28 2008 


Short term... 
(today and tonight) 


Currently...next weak frontal boundary dropping south over the 
eastern plains this morning...and with substantial pressure rises 
over western Nebraska/eastern Wyoming...suspect front will continue to drop 
south...reaching the nm border shortly after sunrise. Other than a 
switch to briefly gusty northwest winds behind the front...little in the 
way of weather across the area this morning. 


Today...very weak/shallow upslope flow develops over the eastern 
mountains and plains by afternoon as cold front washes out just 
south of the nm border. Looking upstream...dewpoints dropping into 
the 30s over the northern Front Range and the northeast plains 
suggest air mass over the plains will be fairly stable today...with 
convection confined to the sangres and points west...where at least 
modest moisture/instability linger. Maximum temperatures look little changed 
from Wednesday readings most locations...with previous set of grids 
looking good. 


Tonight...weak warm advection pattern develops over the east...and 
with old frontal boundary lurking near the nm border...might be 
enough lift to trigger some isolated thunderstorms and rain over the far southeast 
plains after 06z. Added some low probability of precipitation to areas along the nm 
border...but won't spread precipitation as far north as NAM suggests 
yet...going closer to the slightly slower/drier GFS. Will likely see 
at least a middle level cloud deck develop over the area overnight with 
the warm air advection...with some lower stratus potential over the far southeast 
where moisture is deeper. 


Long term... 
(friday through wednesday) 


Friday...flat upper ridge will be over area with a couple weak 
shortwaves moving through the flow across Colorado. NAM has best qg lift in 
the morning with low level southerly flow overrunning old frontal 
boundary producing light precipitation across the southeast plains during the morning 
hours. GFS overrunning is much weaker and farther east. 
GFS...however is stronger with a secondary shortwave/pv lobe moving 
through during the afternoon...suggesting slightly stronger upward 
forcing may be available again by Friday afternoon. Much will depend on 
amount of low level moisture and position of front in the afternoon as 
southerly flow develops and front lifts back northward. Have 
increased probability of precipitation slightly. Southerly flow should also advect higher surface 
dew points into the San Luis valley which should help increase 
potential for thunderstorms across the west as well. Amount of 
cape on the plains will depend on low level moisture. As usual...NAM 
shows higher surface dew points thus greater cape. Model soundings 
show little if any capping in both NAM and GFS. Deep layer shears 
appear marginal for widespread organized severe potential (around 
20-30 kts)...but convective available potential energy could be approaching 1000-1500 j/kg across 
the eastern mountains/plains depending on surface dew points. So could see 
some marginal pulse type severe storms on Friday with hail and 
locally heavy rainfall the main threats. 


Southerly winds increase for Saturday as the upper ridge shifts 
eastward into the Central Plains and next trough approaches the West 
Coast. Warmer air advects in from the west and with deep mixing 
should see a rebound in maximum temperatures. Low level moisture will mix out 
across the mts/adjacent plains with dry line setting up across the 
eastern plains probably near the Colorado/Kansas border. Thus should see a 
decreased coverage of afternoon thunderstorms...so will keep some low 
grade isolated probability of precipitation restricted to mountain areas only. 


Long range models appear in surprising agreement in dropping the 
next trough through the Pacific northwest on Sunday and closing it off 
across the northern Great Basin by Monday. Both models indicate an 
increase in moisture from the south on Sunday especially across the 
western mts. Conceptually southwest flow over the area would 
suggest best potential for thunderstorms for the western areas 
depending on timing of moisture...with dry downslope flow across the eastern 
mts...and potential for dry line to set up somewhere across the 
southeast plains. For now both GFS/European model (ecmwf) suggest dry line will be 
positioned farther west on sun likely somewhere across the Colorado 
eastern plains...then the dry line shifts to near to Colorado/Kansas border 
on Monday as upper low approaches and flow aloft becomes more 
southwesterly. These details are likely to change from run to 
run...depending on timing/position of upper low. The more southerly 
the upper level flow is...the more likely the dryline is to remain 
somewhere across southeast Colorado. For now...have increased probability of precipitation for the 
western mountains and far eastern plains on Sunday. Have left 
isolated probability of precipitation for Monday across the plains as dry line is projected to 
mix eastward towards the Colorado/Kansas border. Main sensible weather 
these days besides the increase in probability of precipitation for the west...will be an 
increase in winds. This could heighten fire weather concerns west 
of the dry line if fuels become critical. Maximum temperatures ahead of this 
system don't look as warm as they conceptually could be...so for now 
the threat appears marginal...but it bears watching. Current fuels 
Page indicates most of the area has greened up from recent 
rainfall. As flow aloft increases...concern increases for severe 
thunderstorm potential east of the dry line where ever it sets up as 
well. For now...appears this threat may stay east of the forecast area. 


Front drops through the southeast plains Monday night...as upper low moves 
across Wyoming and into the northern High Plains on Tuesday. Dew points actually 
dry out behind the front...so this will result in cooler conditions 
for Tuesday/Wednesday with a decrease in probability of precipitation. -Kt 


&& 


Aviation... 
VFR all areas today...with just a low threat of late afternoon thunderstorms and rain 
at kals as storms that form over the sangres drift westward. Will 
likely see broken-overcast VFR ceilings tonight as moisture begins to return 
northward...with potential for some isolated MVFR or IFR ceilings east 
of kcos and kpub by early Friday morning as stratus deck develops 
over the plains. 


&& 


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


$$ 


10/31 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)