043 
fxus63 koax 191535 
afdoax 


Area forecast discussion 
National Weather Service Omaha/valley NE 
1035 am CDT Friday Mar 19 2010 


Discussion... 
first band of snow moving through northern half of the County warning forecast area this 
morning will likely dissipate/weaken through 18z. This band has produced 
some light snowfall amounts...as high as 2 inches based on coop 
reports...although calls to local dispatch indicated recently only 
one half inch amounts or so...with no major problems just yet. 


Focus will shift to developing bands of snow across south central 
Nebraska...as this shifts east northeast along the i80 corridor 
this afternoon. Far southeast Nebraska and southwest Iowa may not 
see any precipitation until evening. Attention then shifts to southeast 
Nebraska and southwest Iowa this evening and overnight...where 
there is a bit better potential for accumulating snow due to the 
snow coming during the nighttime hours. 


Regarding headlines...have held off for now...but may need to 
issue something later this afternoon. Would like to see how the 
bands develop across south central Nebraska...and their impacts. 
The problem...these bands will be affecting the i80 area along 
with the Oma/lnk metropolitan areas at rush hour. So even though amounts 
may be on the light side...2 to 3 inches along i80...the travel 
impacts may be such that we might need ad advisory for this area 
through middle evening. Further south...based on what the GFS may 
suggest...along with the NAM...will likely have an advisory for 
higher snowfall amounts across southeast Nebraska and southwest 
Iowa...but again will wait for a couple hours yet to get some 
additional data. 


&& 


Previous discussion... /issued 335 am CDT Friday Mar 19 2010/ 


Discussion... 


Synopsis...00z upper air analysis indicated 110 knots 300 mb jet diving southward through 
the northern rockies. Downstream...a 100 knots 300 mb northern plains jet extended from 
the Dakotas into the Great Lakes. Two well defined shortwave troughs 
were associated with the jet...the first over Nevada and the second over 
Idaho. At 700 mb strong thermal gradient extended from northern Colorado into eastern South Dakota with 
a decent amount of middle level moisture behind it. At 850 mb initial 
cold front extended from southern Minnesota into NE Colorado with the second cold front over northern 
ND. 08z surface analysis indicated cold front from central Iowa into southeast Nebraska. Regional 
radar mosaic indicated a persistent band of precipitation over northern Nebraska. 


Forecast...going forecast looks generally on track for today and 
tonight. Surface cold front will continue to race southward through the day today. Upper level 
heights will also be falling through the day and this will allow for strong 
middle level thermal gradient to drop southward as well. This will be the 
primary forcing mechanism for precipitation for today. County Warning Area will generally 
see a lack of strong q-g forcing today as the two previously 
mentioned shortwave troughs remain well west of the forecast area. There is some 
support for large-scale ascent over the forecast area today as Nebraska/Iowa will 
reside in the right entrance region of the northern plains jet. Cross 
sections across the frontal zone indicates a well developed frontal 
circulation...but fairly stable as most of the epv remains above 
zero. Nevertheless...given the marginally favorable large- scale 
forcing and strong frontogenesis...shld see widespread precipitation move 
through the forecast area today. Timing of change over from rain to snow looks pretty 
consistent from previous forecast and little change was made here. 
Precipitation shld start off frozen in NE Nebraska this morning...change around 
16-18z alng I-80...and closer to late afternoon over the far S. 


Snow amounts are still a little problematic. Surface temperatures over the western 
forecast area will fall faster during the day...and thus snow will have a better 
chance of accumulating. Alng and east of Highway 75...temperatures shld 
remain generally in the middle 30s and thus accums will mainly be on 
grassy sfcs. Thus have 2 to 4 going in the west today...and 1-3 in 
the east. Northern winds will also be breezy today with 15-30 miles per hour 
expected. We are not expecting much in the way of blowing snow though 
due to the fairly wet nature of the snow. Thus will not issue an advry 
at this time...but the western forecast area will have to be watched today. 


Middle level frontogenesis band then drops into the southern County Warning Area this evening. 
Precipitation change to snow shld be complete by middle evening there. Middle level 
frontogenesis band will likely stall for a time this evening over the southern 
County Warning Area as western US developing trough starts to bottom out and shift slowly 
eastward. This is a little concerning as this cloud lead to more than a 
few hours of strong lift. Also the stability gets weaker as the fnt 
drops farther south. This alng with a good part of the snow falling 
while dark allows for higher accumulations. Once you are able to 
accumulation an inch of two...warm ground temperatures have little further 
affect. Have a general 3 to 6 inch this area from fby to bie to afk 
to rdk and S. Thought about a wntr strm watch for this area as 
some concern that some amounts cloud get close to 6...but will hold 
off and let the day shift today another look. Certainly some type 
of advry will be needed later. 


As system moves into the Southern Plains on Sat...forcing will shift southward 
and clearing shld move in from the north. Other than increasing some 
highs on sun/Mon...little change to the forecast past Sat. 


Boustead 


Aviation... 


Taf sites kofk/koma/klnk 


06z tafs 


Cold front had moved through all three sites at 07z with increasing 
north winds through 12z. MVFR conditions expected to spread south and 
into all sites after 12z with rain/snow after 15z and all snow after 
18z. Occasional IFR ceilings and visibilities after 18z. 


Fobert 


&& 


Oax watches/warnings/advisories... 
NE...none. 
Iowa...none. 
&& 


$$ 


Dewald 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)