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Area forecast discussion...corrected time of issue 
National Weather Service Bismarck ND 
230 PM CDT Wednesday Jul 23 2008 


Short term...today through Saturday night... 
the forecast concerns for this period are chances thunderstorms 
tonight and again tomorrow afternoon. 


An unstable atmosphere is still in place after the mesoscale convective system moved through 
last night into this morning. A developing cool front sits to just 
our west along the Montana/North Dakota border. Dew points ahead of 
the front remain in the lower to middle 60s while behind the front they 
are in the middle to upper 50s. A strong convective available potential energy remains in place ahead 
of the front but sufficient cape...2000+...and bulk shear...25 to 
35kts...is expected for the development of severe thunderstorms late 
this afternoon west and early this evening across central portions 
of the state. The main impulse moving this front through will lift 
farther northeastward into Canada by this evening. Thunderstorms 
chances decrease tonight from west to east as the storms become more 
elevated. 


The front will be along a line from Devils Lake to Jamestown by 12z 
Wednesday were thunderstorms may still be ongoing. A second impulse 
now moving into the Pacific northwest coast will move through 
tomorrow afternoon and evening. Enough instability will be in the 
area for more thunderstorms during this time period. Not expecting 
any severe thunderstorms tomorrow. 


Ridging starts to build back into the region late Thursday as the 
upper level system passes to our East. Heights will slowly rebound 
Friday before another system looks to push the ridge back down again 
as it approaches the northern plains late in the day on Saturday. 
Expect temperatures to be near or slightly above climatology 
throughout the short term. 


Long term...Saturday through Wednesday... 
main upper level Hudson Bay low and low off West Coast of North 
America with weak broad ridge over central North America. Kept 
precipitation chances over western North Dakota for Sunday through 
Tuesday...with models strengthening the ridge on Wednesday. In 
central/eastern North Dakota...kept mention of thunderstorms out on 
Sunday/Monday as ridge deviates from zonal to northwesterly...with 
more influence from the western edge of the Hudson Bay low. 


Seasonable temperatures with highs mainly in the 80s and lows around 
60. 


&& 


Aviation... 
surface low over eastern Saskatchewan and through the western 
Dakotas. This feature is forecast to move into central North Dakota 
by midnight tonight and move into the Red River valley before noon 
on Thursday. Main aviation hazards include showers and thunderstorms 
and accompanying low clouds. The main areas of showers and thunder 
over central/eastern North Dakota will move east into the Red River 
valley today associated with an upper level disturbance. 
Redevelopment of thunderstorms expected along and east of the 
surface low/trough over western and central North Dakota by 
early/middle afternoon...some of which will likely be severe with winds 
gusting to 60 miles per hour and heavy rain. Another upper level wave was 
associated with thunderstorms in southeastern Saskatchewan early 
this afternoon. This area is expected to move east across northern 
North Dakota. Strong southeast winds ahead of the low will extend to 
from 1000 feet to beyond 5000 feet in excess of 40kts - the low 
level jet ahead of the system. 


&& 
Hydrology... 
precipitable water values approaching 1.90 inches...strong Theta-E 
advection and moisture flux ahead of the cold front across western 
North Dakota point to heavy rainfall and possible flash flooding as 
a threat with thunderstorms that do develop east of the 
aforementioned front. The heavy rainfall threat is also supported by 
dominant warm precipitation processes in thunderstorms that do 
develop with low centroid cores below the hail production zone with 
a deep in cloud warm layer with freezing levels near 16 kft...thin 
cape profiles...slow storm motion and k-index values near 40. 
Furthermore... any thunderstorms that develop over a 50-70 mile wide 
swath of 1.00+ inch rainfall amounts from early Wednesday morning 
from Lignite to Wing will pose a flood threat on already saturated 
soils. Jamestown received 1.59 inches of rainfall between 18-1852z 
as result a of a low centroid thunderstorm within the above storm 
environment. A urban and small stream flood advisory is in effect 
until 4 PM CDT for the southern two thirds of Stutsman County. 
Additional thunderstorms over this area will have to be closely 
monitored for flooding potential. 
&& 


Bis watches/warnings/advisories... 
none. 
&& 


$$ 
Hw/DC/jv/PA