000 FXUS63 KTOP 052112 AFDTOP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 312 PM CST Thu Dec 5 2013 .SHORT TERM...(This Evening through Friday) Issued at 207 PM CST THU DEC 5 2013 Mid level shortwave responsible for the chance of snow tonight is currently located over NM and is forecast to lift northeast across KS. Mid level lift increases ahead of the approaching shortwave later this evening allowing snow to develop aloft. The snow may have trouble reaching the ground as forecast soundings show rather dry air in the lower levels it will have to overcome. Short term models continue to show reflectivity spreading into the area from SW KS later this evening which may only amount to flurries especially along and south of interstate 70. After 06z tonight as the shortwave passes more wide spread snow begins to develop across SE KS with the best chances remaining along and south of interstate 35. Behind the wave another reinforcing shot of cold air advects drier air into the region from the north tomorrow morning also limiting the northern extent of the snow. The snow should tapper off for the southeast counties around mid day tomorrow with totals ranging from a dusting to one inch. The 12z MOS guidance was much colder overnight than previously expected therefore have lowered temperatures a few degrees for tonight. Although given the cold air mass and snow cover located over northern NE this seemed reasonable. Decided not to go as low as MOS guidance given that cloud cover may moderate temps and the winds keep the boundary layer mixed, both limiting any enhancement from radiational cooling. Ultimately, think low temperatures tonight will range from near zero in north central KS to the low 10s in east central KS. Wind gusts will pick up overnight to around 20 mph as the wave moves across the region which will bring wind chill values down into the -0s to -10s by sunrise. The clouds will continue to hang around most of tomorrow morning but begin to clear out during the afternoon and evening hours. High temperatures tomorrow will remain in the mid 10s to near 20 as the cold air continues to filter into the region from the north with wind chills in the 0s. .LONG TERM...(Friday Night through Thursday) Issued at 207 PM CST THU DEC 5 2013 Fri night-Sat night: Cold high pressure continues to move southward into our area Friday night into Saturday morning. Current temperatures under this high currently up over southern Canada are in the negative teens. Despite moderation as it moves southward, with clearing skies have gone on the cold side of guidance with lows -3 in the NW to about 4 above in the southeast. Clouds on the increase from the west through the day Saturday will also hinder a warmup and have gone on the cool side for highs with 18-21 across the area which may still be too high. Expect temperature to then stall a bit for the night Saturday night as clouds and chances for snow move in from the west. Sunday/Monday: Upper trof moving in for Sunday is also driven by phasing with smaller and larger scale trofs to the north, and guidance suggest a leading ripple of energy to cross the cwa overnight before energy rotates out of the base of the larger trof and over the forecast area Sunday afternoon and evening. Not a tremendous amount of moisture for this system to work with, but what comes in with the system and is able to interact with the dynamics looks to be enough to produce generally 2-4 inches of snow across our area. Northwest zones progged to get a few inches with the first wave evening to early morning hours, with the remainder of the area getting a few inches overnight into Sunday. Far SE counties soundings suggest drying out in the mid levels, but appears to be enough cold air down low to counter freezing drizzle changeover chances, and just will carry a snow or freezing drizzle wording across the farthest SE areas. Frontogenetic forcing doesnt align with instability in the column this far north, but rather snowfall appears driven by the frontogenesis / qvector convergence moving through with the waves, and banded heavy snow is not anticipated. Highs in the 20s forecast for Sunday. Incoming colder air behind the passing wave drops overnight lows Sunday night back into the single digits to low teens, with teens for highs on Monday. Tues-Thurs: Tuesday and Wed both GFS and EC slowly take the upper trof across the area with temperatures only making slight improvements through this period. Thursday may bring either more zonal flow or a ridge aloft over the state and may moderate temperatures a few degrees higher for Thursday but a bit far out to be too optimistic. && .AVIATION...(For the 18Z TAFs through 18Z Friday Afternoon) Issued at 1126 AM CST THU DEC 5 2013 VFR conditions expected through the taf period. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Sanders LONG TERM...67 AVIATION...Sanders