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Area forecast discussion 
National Weather Service Topeka Kansas 
525 am CST Friday Jan 9 2009 


Update... 
updated the aviation discussion for the 12z tafs. 


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Discussion... 
see previous discussion. 


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Aviation 
anticipate VFR conditions to prevail until the frontal passage...which appears 
to be a touch faster than the previous tafs had. Low level wind shear will continue 
to be a problem until the nocturnal inversion mixes out...so have 
maintained low level wind shear until 15z. A strengthening pressure gradient will 
cause winds to gust to near 30kts from the north behind the front. 
Forecast soundings continue to show ceilings coming in around 2 kft 
too...though the low ceilings appear to lag the winds shift by a couple 
hours. Am a little concerned for a trace event of light freezing 
rain or snow flurries occurring in the 00 to 04z time frame as 
models show an axis of strong middle level frontogenesis moving across. 
06z NAM has trended dryer in the middle levels. Confidence in precipitation 
occurring is low so have not mentioned it in the tafs. 


Wolters 


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Previous discusiion.../310 am CST Friday Jan 9 2009/ 
today/tonight...little change to forecast reasoning in the morning 
package. Southerly winds continue to advect warmer air into the County Warning Area 
this morning with temperatures steady or slowly rising early this 
morning. As of early this morning...readings were mild in the middle 
30s to lower 40s. A cold front originating from the northern plains 
is expected to move through the County Warning Area beginning late this morning in 
far north central Kansas and slide through the remainder of the area 
this afternoon. In advance of the frontal boundary...temperatures 
will warm into the upper 40s in NC Kansas to the upper 50s in ec 
Kansas. Behind the front...modest pressure rises on the order of 
3-4hpa increasing to 6-7hpa by evening will occur along with a 
unidirectional northerly wind profile from 0-3kft and 30+kts at 
1500ft will owe to breezy northerly winds of ~15-20kts with higher 
gusts during the afternoon into the majority of tonight. In addition 
to the wind...cooler air will advect into the County Warning Area with lows tonight 
into the upper teens to lower 20s. As for precipitation 
potential...not looking very promising. Overall...the system is out 
of phase to produce measurable precipitation. As the strongest 
low-level lift moves through in the form of the surface cold front...the 
vertical moisture profile remains fairly dry. Within the 
Post-frontal regime...good saturation occurs between h9-700 mb but 
downglide is in place by this time. There will however be a response 
with increasing cloud cover behind the front...with mostly cloudy 
skies expected across most of the area tonight. It is conceivable a 
few sprinkles may occur across the far north and northeast County Warning Area but 
confidence is too low to mention in forecast at this time. Flurry production 
seems unlikely as temperatures do not cool sufficiently for ice 
production in the saturated layer until Sat morning when drier air 
begins to advect into the area. 


Saturday/beyond...brisk northerly winds will continue during the day 
on Saturday with temperatures struggling to reach the lower to 
middle 30s. Models differ on the speed in clearing out the low level 
cloudiness that is expected to be in place at the start of the 
period. However...the overall trend should be clearing skies as the 
morning/afternoon progresses. 1028hpa surface high builds in Sat night 
and surface winds fall under 5kts. Thereafter...northwest flow continues 
through the majority of the upcoming work week. Models continue to 
show a polar 1050hpa high dropping into the central Continental U.S. By 
midweek. This will potentially bring very cold air back into the 
region...albeit the lack of snow cover may help prohibit magnitude 
somewhat. Regardless...future model runs will determine whether the 
axis of coldest air will reach the area or slide off to the east. 


Blair 


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Top watches/warnings/advisories...none. 


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