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fxus63 kbis 212040 
afdbis 


Area forecast discussion 
National Weather Service Bismarck ND 
240 PM CST Sat Nov 21 2009 


Short term...tonight through Tuesday night... 


Models start out in good agreement but subtle differences begin 
to appear by Sunday night leading to reduced forecast confidence. 
The biggest forecast concerns are chances of precipitation Sunday 
night through Tuesday night. 


Currently...there is a surface low moving through eastern 
Saskatchewan towards Lake Winnipeg in Manitoba. The associated 
cold front has pushed into western North Dakota through Dickinson 
and will continue moving east tonight. A strong pressure gradient 
and mixing of the lower atmosphere behind the cold front have 
caused strong west-northwesterly winds. Ahead of the front...the 
strongest pressure gradient has already pushed into eastern North 
Dakota. The cold front is forecast to be along a line from Minot 
to Bismarck by 00 UTC Sunday and near Jamestown by 06 UTC...and 
the atmosphere should decouple this evening and end the gusty 
winds. 


An upper level trough associated with the aforementioned low 
pressure system moves through North Dakota tonight and short wave 
ridging moves through the region in its wake. Ridging is short-lived 
as another disturbance approaches for Sunday night into Monday. 
The 12 UTC GFS and European model (ecmwf) begin to disagree at this point with the 
path of the trough. The European model (ecmwf) drops this trough farther to the 
south into Nebraska and paints precipitation across mainly 
southeastern North Dakota tonight into Monday morning. The GFS 
moves the upper level low through South Dakota and shows some 
light precipitation across western and central North Dakota. With 
models split on the path of this system...gridded forecasts have 
only a slight chance of precipitation for Sunday night. The 
exception is in far southwest North Dakota where precipitation 
chances are slightly higher due to model/ensemble overlap there. 
Guidance supports more disturbances moving through the northern 
plains through Tuesday night...justifying chances of 
precipitation and slightly cooler temperatures. That 
said...temperatures should remain above average through most of 
the period. 


Long term...Wednesday through Saturday night... 


The long term begins Wednesday with the models depicting a low over 
the middle-Mississippi Valley/Great Lakes area and dry northwesterly 
flow over North Dakota...with ridging to the west. The GFS keeps 
this upper level ridge axis to our west until Friday...then brings 
the next upper level shortwave across southern Saskatchewan and 
Manitoba. The European model is faster with the upper level ridge 
axis...but then develops the next shortwave farther south near 
Colorado and the 4 corners area by Saturday. Thus will keep the 
forecast dry throughout the extended period. 


The upper level ridging on Thursday - Thanksgiving day - will bring 
mild weather to North Dakota. Expecting average to above average 
temperatures...with morning lows in the upper teens to lower 20s and 
highs from the middle 30s east to upper 40s southwest. In fact...most 
of the extended should see highs 35 to 45 for most days and lows in 
the teens and 20s. Averages for this time of year are generally 
highs in the lower 30s and lows in the teens. 


&& 


Aviation... 


A surface low over Saskatchewan is forecast to move eastward into 
Manitoba tonight. A trough extending southward from the low will 
continue pushing eastward across the Dakotas and into Minnesota by 
around 06z. Expect trough to move through kbis and kmot by around 
00z and kjms after 03z. Gusty south winds ahead of the trough...with 
gusts to 30kts at kjms...and gusty west winds behind it through 
02z...then wind speeds decreasing. Expect mainly high cirrus clouds 
with scattered middle clouds 10000-15000 feet. Some scattered clouds 
3000-5000 feet moving into the state after 10z. Lighter southwest winds 
on Sunday. 


&& 


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


$$ 


Synopsis/short term...DC/scheck 
aviation...DC/jv 
long term...jv