Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 242343
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
542 PM CST Wed Dec 24 2014
...Update to aviation forecast discussion...
.SHORT TERM...(This Evening through Thursday)
Issued at 321 PM CST WED DEC 24 2014
System is kicking out of area with surface ridge axis moving
eastward across western portion of forecast area at mid-afternoon.
Back edge of stratus appears to be correlated with the surface ridge
axis and should be moving through Manhattan by 5 PM and through
Topeka by about 8 PM. Temperatures may fall quickly this evening
and then slowly warm as pressure gradient and associated winds
increase overnight, resulting in considerable mixing. Lows tonight
somewhat tricky as a result, but have gone mostly mid to upper 20s
over the area.
On Christmas day, the pressure gradient between lee low and
departing high is strong enough that southerly winds are expected to
be in the 20 to 30 mph range with higher gusts from late morning
through mid to late afternoon. Extensive cirrus shield ahead of
next upper trough will bring increasing high-level cloudiness on
Thursday. Max temps are expected to be in the mid to upper 40s
along the Nebraska border to the lower 50s along and south of I70.
.LONG TERM...(Thursday Night through Wednesday)
Issued at 321 PM CST WED DEC 24 2014
Thursday night the upper longwave trough moves into the southwest
US, while a lead shortwave ejects into the plains passing north of
the area. This will push a cold front into the area during the day
Friday. There is fairly good agreement among the models with the
temperatures through the course of the day. How that energy lifts
out of the southwest is the main concern with this period. Another
shortwave looks to pass north of the area Friday afternoon and
evening bringing a round of light snow to north central KS. Behind
the front and further southeast low level moisture and isentropic
lift may cause light rain and or drizzle for mainly areas along and
east of the turnpike Friday afternoon. Temperatures will be well
above freezing during this time frame. The large scale lift
continues to increase into the overnight hours allowing more of a
rain or snow mix as the pattern progresses. The change over to snow
will depend on how fast the cold air can move southward. By midnight
Saturday the freezing line appears to reach the turnpike, with
locations starting to clear out in north central KS. A rain snow mix
will continue to be possible through Saturday evening in southeast
portions of the forecast area as the positively tilted trough
progresses eastward through the central US. Lift is not
particularly strong with this system, which means light precip
amounts expected at this time with generally less than one inch of
snowfall for most areas.
For the extended the west coast ridge becomes amplified allowing a
better connection to the cold air. As shortwaves dig into the long
wave trough over the southwest US the models begin to disagree on
cutting that energy off or bringing out a much stronger system. As
for now a lead shortwave looks to eject out of the central Rockies
bringing a chance for light snow mid week. Rather or not that is a
quick hit or something more significant is in question. Temperatures
will be below normal next week with highs in the 20s and 10s and
lows in the single digits.
.AVIATION...(For the 00Z TAFs through 00Z Thursday Evening)
Issued at 529 PM CST WED DEC 24 2014
Currently the stratus clearing line remains on track to bring VFR
conditions to all TAF sites. KMHK is clear and will stay that way.
KTOP and KFOE will be in the clear by 02z. Expect winds to be the
main area of concern but gusty from the South on Christmas Day.
The only real area of uncertainty at this point will be the
possibility of LLWS over the KTOP/KFOE terminals by about 10z in
the morning. Have not added this for now due to uncertainty in the
winds forecast by the model. However, the current model run does
appear to have the winds in the lowest 2kft about 10 kts too low
in comparison to the 0z sounding just released.