985 
fxus63 kbis 212058 
afdbis 


Area forecast discussion 
National Weather Service Bismarck ND 
358 PM CDT sun Mar 21 2010 


Synopsis... 
high pressure over Minnesota and Iowa with low pressure in Alberta. 
Weak pressure falls over northern plains with slow moving weak 
clipper forecast to hit North Dakota on Monday. 
&& 


Short term...tonight through Wednesday night... 


Currently...upper level ridging is attempting to nudge into the 
northern plains from the southwest...between troughing over the 
eastern US and another low moving on shore in the Pacific 
northwest. Resulting west to northwest flow aloft will be the 
steering flow for a couple of impulses that are expected to 
traverse the state through Tuesday night. At the 
surface...observations indicate a residual frontal boundary lying 
along the international border...and a developing Lee-side low in 
southern Alberta. Warm advection south of the front has brought 
temperatures up into the upper forties in the east to middle 50s in 
the west. 


Models are once again in very good agreement...so will continue to 
utilize a general blend for the forecast. Main forecast concern will 
be the precipitation amounts expected with the passing of a clipper 
type system Monday through Wednesday. 


As the main trough moves onshore this evening...models indicate a 
shot of energy moving out of the trough and quickly traversing The 
Rockies. The impulse bumps the surface low off to the 
southeast...and the two travel together...eventually crossing the 
Montana/ND line Monday morning. As the low continues to the 
southeast...the impulse will likely move east directly across the 
frontal boundary still in place along northern ND. This is expected 
to focus an area of light rain along the northern half of the state 
Monday morning and afternoon. Monday night...the low should be well 
off to the east...however...the main upper level trough then begins 
to cross The Rockies and enter the County Warning Area...resulting in a chance of 
precipitation that persists until Tuesday night for most of the forecast 
area...especially in the west where forcing appears to be strongest. 
Most precipitation will likely fall as rain...but as cooler temperatures settle in 
behind the surface system...may see a changeover to light 
snow...however...no accumulations are expected. Total precipitation through 
Tuesday night could approach around a quarter inch in the north and 
west...with lighter amounts elsewhere. 


Wednesday...northwest flow aloft returns to the forecast area. 
Models depict another system...much weaker than the 
previous...passing off to our north and bringing a slight chance of 
precipitation to my northern counties. Otherwise...temperatures on 
Wednesday should be quite warm for this time of year...as upper 
level ridging and southwest surface winds will likely result in 
plenty of warm advection. 




Long term...Thursday through Sunday night... 
the GFS and European model (ecmwf) forecast models remain in agreement in regards to 
the overall large scale pattern for the extended period. There are 
once again some differences regarding smaller scale features which 
should be resolved as we progress in time. 


The region will remain under the influence of northwesterly flow 
aloft through most of Thursday as an upper level ridge axis stays 
off to our west. This pattern should maintain mainly dry conditions 
as well as below average daytime highs thanks also to a back door 
cold front lingering over the region. Resultant temperatures will 
range from the low 30s northeast to near 45 far southwest Thursday. 
Expecting a brief moderation in temperatures Friday as a middle level shortwave 
impulse and another weak cold front slowly pushing across the 
northern plains from Thursday night into Friday night. This disturbance 
will bring another chance for light precipitation Thursday night-Friday 
night...along with another surge of cooler temperatures for Saturday 
with highs dropping/averaging slightly below normal. 
Nighttime/morning lows look to remain subfreezing through Sunday 
morning. 


Forecast model guidance continues indicates a much stronger 
moderation in temperatures beginning Sunday and continuing into 
early next week as a broad upper ridge builds east into the northern 
plains. 


&& 


Aviation... 
a middle/upper level short wave trough will slide into the northern 
plains region tonight into Monday...bringing increasing clouds as 
well as increasing chances for precipitation from west to east. Ceilings 
are forecast to remain mainly VFR...although MVFR ceilings will become 
increasingly possible Monday morning into Monday night. 


&& 


Hydrology... 
warmer temperatures today have not increased river flooding on 
gauged sites. However overland flooding continues in the south 
central as well as 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 North Dakota Apple Creek near Menoken had 
fallen below flood stage but was forecast to rise to above 15 feet 
again this week. Flooding also continued on Beaver Creek at Linton 
and Apple Creek near Menoken remain above floods stage. Beaver 
Creek below Linton fell below major flood overnight into the 
moderate flood category. The stage Sunday morning was 12.1 feet. 
Flood stage is 9 feet. The river is forecast to begin rising again 
Sunday afternoon and crest again in the major flood category at 14 
feet on Wednesday evening the 24th...then begin a slow fall. 


In addition warmer temperatures today and forecast even warmer high 
temperatures on Monday have increased the risk for overland and ice 
jam flooding on the rivers and creeks of most of southwestern North 
Dakota where a moderate snowpack continues to exist. 


&& 


Bis watches/warnings/advisories... 
Flood Watch through Tuesday morning for ndz017>020-031>034- 
040>045. 


&& 


$$ 
Hw/bpn/NH