Area forecast discussion 
National Weather Service Omaha/valley NE 
1121 PM CST Friday Jan 30 2015 


Update... 
issued at 907 PM CST Friday Jan 30 2015 


The overall trend of the forecast remains on track with 
precipitation spreading northeast out of central Kansas...then 
developing north toward the NE/South Dakota border region. Believe precipitation 
type will be the issue and possible changeover time which 
complicates the forecast. 


00z NAM remains very aggressive with precipitation development with 0.88 
inches of quantitative precipitation forecast at koma through 48 hours. BUFKIT soundings suggest 
a fairly rapid changeover to snow with strong dynamical cooling 
taking place across the region...with about 4 g/kg of specific 
humidity noted on the 290k isentropic surface so there is plenty 
of moisture to work with. Indeed...00z subjective upper air 
analysis indicates fairly deep and saturated moisture streaming 
northward with about 0.6 to 0.8 inches of precipitable water...which is in the 
97.5-99 naefs precipitable water climatological percentile along and south of i80. 
An initial concern is that precipitation could potentially change over 
to all snow earlier than forecast resulting in higher snowfall 
totals. The second concern is the rather deep saturation that is 
prognosticated to overspread the region resulting in higher quantitative precipitation forecast than 
forecast. Model suites are all generating 0.7 to 0.9 inches of 
quantitative precipitation forecast and our forecast remains below that by about one quarter 
inch. One mitigating factor is the sref probability of 
accumulation on roads product remains low much of the day 
Saturday...holding off until well after dark before roadways 
become significantly impacted. That doesn't mean would wouldn't 
still be able to accumulate snowfall on grassy surfaces though. 


Will wait for GFS...sref...hires and European model (ecmwf) models before making 
major changes...but initial thoughts are that quantitative precipitation forecast/snow amounts 
may need to be raised. Early in the event...winds will also remain 
generally light less than 10 miles per hour which will help quite a bit. 
Current storm total snowfall forecast ranges from 1 to 4 inches 
across the region...but again...will wait for complete model 
suites to make any upward adjustments. 


&& 


Short term...(tonight through monday) 
issued at 310 PM CST Friday Jan 30 2015 


Precipitation type and precipitation amounts will be the main concern in this period... 
especially from late tonight into Saturday evening. Precipitation should turn 
to mostly snow by late Saturday night all areas. 


Water vapor loop and latest rap model initializations showed a 
closed low over the California/Arizona border region early this 
afternoon. This will drop southward into Mexico through Sunday. Some 
shortwave energy will move northeast out of this trough though and 
move up into the Central Plains later tonight and Saturday. Surface 
analysis early this afternoon showed modest south/southwest winds 
spreading across our area. Clouds will thicken and lower...with 
light precipitation probably moving into our southern counties before 12z. 
Have lows forecast in the upper 20s north and lower 30s south. The 
precipitation type may be a mix later tonight into Saturday. 


Did make some modifications to snow amounts...mainly for Saturday 
night into Sunday morning. On Saturday...it appears that if we get 
any accumulations...they would be light and mainly on grassy areas 
for our southern zones. Farther north...precipitation chances will be 
increasing in the afternoon but amounts would be lighter. The NAM 
forecast soundings still appeared too cold...and went closer to a 
blend of some of the other models...especially the sref. North 
winds will spread across the area Saturday night...and as the 
column cools...precipitation will change to mostly snow and will start to 
accumulate. A separate system will drop quickly southeast in the 
northwest flow Saturday night...providing good lift in a favorable 
environment for snow from the northern parts of northeast Nebraska 
into west central Iowa. Increased snow amounts for areas along and 
north of Highway 20. It appears another lobe of lift will drop 
down over parts of the area Sunday afternoon...so kept some 
mention of light snow going until Sunday night. Sunday night is 
expected to be cold with decreasing clouds and decreasing winds. 
Lows should drop to the single digits and we may see some below 
zero numbers from Hartington and Wayne toward Tekamah and Harlan. 


Fast northwest flow in the middle levels will be in place for Monday 
and it does appear that a shortwave trough could move through our 
area. Models...especially the 12z GFS...bring some light snow in 
for Monday afternoon. Could not argue with that too much so went 
with a slight chance of light snow for now and will fine tune that 
later. Measurable light amounts seem possible...especially in 
western Iowa Monday. Highs Monday will be mostly 20s. 


Long term...(monday night through friday) 
issued at 310 PM CST Friday Jan 30 2015 


Some milder air will spread in briefly for Tuesday...with highs 
reaching the upper 30s and lower 40s. Did not want to get too 
optimistic at this point for highs. Another surge of colder air 
will drop down into the area by Tuesday night. Some light snow 
seems possible based on the pattern...plus both the 12z GFS and 
European model (ecmwf) show a bit of snow. 


Temperatures Wednesday and Thursday will be below normal...then 
closer to normal by Friday as south or southwest winds increase. 


&& 


Aviation...(06z tafs for kofk...klnk and koma.) 
Issued at 1119 PM CST Friday Jan 30 2015 


VFR initially. Rain and MVFR ceilings develop at klnk by 10-14z...koma 
14-18z and kofk 15-19z. Should start to see snow mix with the rain 
by 21-00z...changing over to all snow. Winds southerly initially...then 
backing becoming southeast...east...and eventually northeast and 
substantially increasing at kofk toward the end of the period...and 
at klnk/koma just beyond the end of the taf period. 


&& 


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


$$ 


Update...Dewald 
short term...Kern/Miller 
long term...Miller 
aviation...Dewald 






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