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Area forecast discussion 
National Weather Service Pueblo Colorado 
252 PM MDT Friday Jul 18 2008 


Short term... 
(tonight and saturday) 


Forecast challenge is again thunderstorm coverage 


Currently two upper features working on forecast area producing 
isolated to scattered thunderstorms. First feature is a plume of 
moisture that extends into southern Colorado from norther New 
Mexico and Arizona. Thunderstorms developing mainly over southern 
sangre Delaware cristo mountains and Pikes Peak/Palmer Divide. Second 
feature is a short wave working into western Colorado producing 
thunderstorms along Continental Divide. Surface dew points remain 
in the 50s over the plains with 40s to the west. Plenty to work 
with if we can get the upper support. 


Tonight...looks like southwest plume will veer east and affect 
mostly southern areas while western short wave impact central 
mountains and north. Raised probability of precipitation earlier today to suggest better 
coverage given the two features. Held those probability of precipitation up through the 
evening then tapered them off after 03z. Kept low probability of precipitation along 
southern tier overnight. 


Saturday...wedge of drier air moves into the region as upper high 
rebuild over US. Stayed with current forecast probability of precipitation/temperatures that 
reflect very warm temperatures and dry conditions except for low probability of precipitation 
Southwest Mountains. 


Long term... 
(sunday through friday) 


..hot and mostly dry weather southeast Colorado sun-Mon... 
..A more active thunderstorm pattern still possible Tue-Fri... 


Sunday and Monday...models continue to support the 500mb high 
pressure system to be centered over east Central-Northeast Colorado 
Sunday and possibly into Monday. The deeper ridge of moisture 
will settle further west from Arizona to the Great Basin into western 
Colorado each day. It is possible this moisture ridge may shift a little 
further east on Monday. The combination of daytime heating...weak 
upper level disturbances...and the moisture ridge will support 
thunderstorm develop...primarily along the Continental Divide and 
westward. The thunderstorm steering currents will be westerly(from 
the east to the west) across much of southern Colorado. Surface based 
thunderstorm development across southeast Colorado plains should be at a 
minimum or none given the relatively strong capping inversion 
aloft suppressing any surface based thunderstorm initiation. Any 
thunderstorms that develop over the southeast Colorado mountains will 
move westward and not typically into the I-25 corridor...so the 
threat for precipitation will be very low or none across the I-25 
corridor Sunday and Monday afternoon/evening. The main 
thunderstorm threat across the Continental Divide...especially 
the Southwest Mountains...will be locally moderate to heavy rain 
given 700-500mb specific humidity values of 6-7.5 g/kg...freezing 
level 14k-17k feet mean sea level... and steering currents of 10kts or less. 
Hot surface temperatures will continue within the high pressure 
system aloft given 700mb temperatures of +18c to +21c generally 
along the I-25 corridor and mountains/high valleys. High 
temperatures around 100f will still be likely from Pueblo to La 
Junta Sunday and Monday afternoon. 


Tuesday through Friday...very challenging forecast and it depends 
on actually where the middle to upper level high pressure resides. 
The dgex and European model (ecmwf) continue to project the upper high to shift a 
little further east of The Rockies and would support...albeit weak... 
relatively deep south-southwesterly flow across the Desert Southwest 
into the Great Basin and central rockies. The degree of "monsoonal" 
moisture that migrates into the central rockies is still the 
wildcard for Tuesday through Thursday. The dgex wants to shift the 
700-500mb moisture layer of specific humidities of 5-7 g/kg into 
much of Colorado Tuesday through Thursday. If this occurs... then a 
little higher grade moisture will be across Colorado with the potential 
for moderate to heavy rainfall in a short period of time given the 
ample moisture...freezing level 16k-17k feet mean sea level...and steering 
currents 5kts or less...especially over the mountains/high valleys 
and I-25 corridor. By Friday...there is the potential for the 
upper level high to recenter itself over Colorado. On the other hand... 
the GFS ensemble data suggests the upper high could remain 
directly over Colorado through the period. If this occurs...then the 
high quality moisture will remain to our south and west of Colorado. 
Within the high pressure center...moisture should just recycle 
itself from diurnal isolated-scattered thunderstorms. Temperatures 
should be around or slightly above seasonal "norms" through the 
period. Metze 


&& 


Aviation... 


Scattered mountain thunderstorms until 03z. Isolated over the 
plains. Possible MVFR ceilings over eastern plains after 09z otherwise 
VFR. 


&& 


Pub watches/warnings/advisories... 


None. 


&& 


$$ 


21/17