Weather

124 
fxus63 kbis 282027 
afdbis 


Area forecast discussion 
National Weather Service Bismarck ND 
327 PM CDT Thursday Aug 28 2008 


Short term...tonight through Sunday night... 
models in fairly decent agreement through Saturday. Forecast 
concerns for this period are precipitation chances overnight and a 
continuing fire weather concern through Saturday. 


Currently...shortwave ridging is moving into North Dakota with 
slight zonal to northwest flow aloft over the region. Satellite and 
upper air analysis shows a disturbance moving into western Montana 
this afternoon. A trough is associated with this disturbance and 
will move through North Dakota overnight. Models place a vorticity maximum 
just to the north in Saskatchewan this evening along with favorable 
Omega fields to bring clouds...but isolated showers at best...to 
northern parts of North Dakota overnight. The trough associated with 
this disturbance is expected to exit the region before daybreak 
Friday. Will make a dry overnight forecast for tonight...in part as 
surrounding offices are going dry. 


Weak ridging continues to build across the northern plains on Friday 
with a surface high lifting northeastward out of Wyoming and into 
eastern North Dakota turning winds to southerly flow across the 
area. Winds mixing to the surface in the afternoon in conjunction 
with relative humidities in the 20 to 30 range may cause fire 
weather concerns in western parts. As fire headlines are ongoing 
into this evening...will not headline Friday. 


The 500 mb ridge will slowly Transfer eastward into Saturday 
bringing winds aloft around to the southwest. Lee troughing will 
develop early Saturday and slowly make its way eastward as a 
disturbance ejects out of a large trough moving onto the Pacific 
northwest. By Saturday evening a surface low is expected to develop 
along the Lee trough in southeast Montana...into western North 
Dakota. Warm advection will be strong on Saturday driving 
temperatures into the middle 90s. Winds are again expected to be in the 
15 to 25 miles per hour range...with more fire weather concerns. Weak vertical 
lift will also be in the area Saturday night so a stray shower or 
thunderstorm overnight may be possible. 


Scattered thunderstorms will develop Sunday as the trough digs into 
the intermountain region. This will help push a strong cold front 
closer to the North Dakota border by late afternoon. 


Long term...Monday through Thursday night... 
Labor Day Monday and Tuesday will have a decent chance for showers 
and thunderstorms as a longwave trough over The Rockies sends plenty 
of shortwave energy and moisture to the northern and Central Plains. 
A definite surface front/boundary develops over the Dakotas to 
Wyoming/Nebraska separating warm moist air south and east of the 
front with significantly cooler air to its north and west...for 
example highs Monday from the 60s northwest to lower 80s southeast. 
Have increased chances for precipitation with this system. 


This sharp longwave trough becomes a broad trough as the system 
lifts northeastward...and only small chances of showers/thunder will 
remain for Wednesday and Thursday. Temperatures recovering to the 
70s and lower 80s by Thursday. 




&& 


Aviation... 
fair weather cumulus this afternoon will remain scattered through 
early evening...then dissipate as temperatures begin to drop towards 
sunset. Some weak upper level shortwave energy moving through the 
northwest flow aloft will bring some scattered to broken middle clouds 
later this evening and overnight along with a weak surface trough. 
On Friday another push of dry high pressure will again bring 
northwest winds of 15 to 30 miles per hour with scattered afternoon cumulus. 


&& 


Fire weather... 
red flag warning continues for nine southwest North Dakota counties 
into the evening as critical fire weather conditions exist. 
Decreasing wind and increasing relative humidity will ease critical 
fire conditions this evening. 


Critical fire weather conditions may exist again on Friday and 
Saturday. Temperatures Friday are forecast into the middle 80s...middle 
90s on Saturday...with breezy to windy conditions and very low 
relative humidity both days. 


&& 


Bis watches/warnings/advisories... 
red flag warning until 8 PM CDT /7 PM MDT/ this evening for 
ndz017-018-031>033-040-041-043-044. 


&& 


$$ 


Cousins/Martin/Vining