892 
fxus63 kbis 202101 
afdbis 


Fxus63 kbis 202101 
afdbis 


Area forecast discussion 
National Weather Service Bismarck ND 
401 PM CDT Sat Mar 20 2010 


Synopsis...high pressure over the Central Plains will bring a dry 
southwest flow to western and central North Dakota. 
&& 


Short term... 
currently...upper level trough stretches from the Great Lakes to to 
Texas...resulting in northwest flow aloft over the northern plains. 
A large dome of surface high pressure resides over the Central 
Plains...and with a low pressure area/cold front to the north...the 
pressure gradient over the forecast area has produced a steady 
southwesterly wind across the entire forecast area. The downsloping 
component to the wind has helped to bring temperatures up to the 
upper 30s and lower 40s this afternoon. 


Models are in good agreement during the term...so have continued 
with a general blend for the forecast. Main forecast concerns will 
be warm temperatures up until Monday...then the chance for precipitation as 
a clipper type system sweeps across the state. 


Tonight and Sunday...upper level ridging attempts to nudge into the 
area from the southwest...shifting upper level flow from 
northwesterly to near-zonal. The cold front to the north is expected 
to stall out along the international border as it is cut off from 
its parent system in central and eastern Canada. Therefore...warm 
temperatures and clear skies should remain in place within the 
forecast area. Southwesterly winds are expected to shift more to the 
south by Tuesday morning...and the resultant warm air advection 
should bring tuesday's high temperatures up another 5 to 10 degrees. 


Meanwhile...a Lee-side low is forecast to develop in southern 
Alberta...as an upper level trough begins to move onshore in the 
Pacific northwest. By Monday...the trough lends its support to the 
low and the system begins to track to the southeast into Montana and 
North Dakota. By Monday afternoon...the center of the low should 
move into western South Dakota before continuing south into the Central Plains 
Tuesday. Cold frontal passage is expected sometime overnight 
Monday...and will likely bring a round of colder temperatures for Tuesday. 


Models indicate that there may be two rounds of precipitation 
expected with this clipper. The first round impacts the northern 
half of the state Monday afternoon...and is associated with the 
increased lift along the nearly stationary frontal boundary left in 
place from Sunday. With the warm air in place...most of this precipitation 
should fall as rain...with amounts of a quarter inch or less 
expected as a result. The second round is associated more with the 
upper level system that traverses the area Tuesday...and will occur 
with much cooler temperatures in place behind the surface low. Will 
therefore keep a chance of light snow and rain in the forecast 
through Tuesday night. 




Long term...Wednesday through Saturday... 
the GFS and European model (ecmwf) forecast models remain in pretty decent agreement 
in regards to the overall large scale pattern for the extended 
period. 


The region will be under the influence of northwesterly flow aloft 
Wednesday-Wednesday night as split flow aloft develops keeping precipitation 
chances north and south of the local area. The northern stream 
trough will push a back door cold front into the northeastern half 
of the state later Wednesday...bringing colder middle level temperatures to 
central and eastern portions of the County Warning Area for Thursday. My southwest 
looks to be spared as the cold front stalls over central ND. 
Resultant temperatures will range from the low 40s northeast to low 
50s southwest on Wednesday...then from the low 30s northeast to near 50 
far southwest Thursday. Another weak cold front is still depicted to 
drop south through the region Thursday night-Friday night...bringing 
another chance for light precipitation along with another surge of 
cooler temperatures maintaining highs slightly below normal values. 
Nighttime/morning lows look to remain subfreezing through the 
period. 


Current long range guidance indicates a much stronger moderation in 
temperatures beginning late next weekend and continuing into the 
following work week as a broad upper ridge builds into the northern 
plains. 


&& 


Aviation... 
large high pressure dome across the central US will continue to 
result in VFR conditions for all taf sites in the region. Expect 
continued high clouds across the state...with southwesterly winds 
decreasing some around and after sunset. 


&& 


Hydrology... 
colder temperatures today have decreased overland flooding south 
central however at the same time increased the ice jam flooding in 
the West. 


Point forecast for river flooding continuing for LaMoure on the 
James...Ludden dam on the James and near Pingree on the Pipestem 
creek. 


Pipestem creek is forecast to rise another half foot to near 9.9 on 
3/26. On the James La Moure is forecast to rise to 16.2 feet from 
its current level of 15.4 and Ludden is forecast to continue a slow 
rise to 16.6 feet on 3/28. 


In the south central colder temperatures have reduced overland 
flooding but Beaver Creek at Linton and Apple Creek near Menoken 
remain above floods stage. Beaver Creek is forecast to crest at 
14.0 feet on 3/24 and Apple Creek is forecast to crest at 15.1 feet 
on 3/25 




&& 


Bis watches/warnings/advisories... 
Flood Watch through late Sunday night for ndz017-031-032-040-043. 


&& 


$$ 


Short term/hydrology...hw 
long term...New Hampshire 
aviation...bpn