537 
FXUS63 KTOP 021148
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
548 AM CST Sat Feb 2 2019

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 517 AM CST Sat Feb 2 2019

As of 09Z Saturday morning a negatively- tilted, midlevel trough 
was progressing eastward across the TX Panhandle. Surface low/lee 
trough continues to deepen across the High Plains with continued 
low-level mass response across the Southern and Central Plains. 
Nearly the entire CWA has seen surface temperatures and dew points
rise into the low 40s. Patchy drizzle and fog have been noted 
across the CWA, primarily the southeastern half. The combination 
of weak low-level ascent and shallow moisture has resulted in 
less-coverage of drizzle through the night than previously 
anticipated. Dense fog has been expanding across portions of 
Central KS and East-Central KS, as a result have issued a Dense 
Fog Advisory through 10 AM for Morris, Lyon, Coffey, Osage, 
Anderson and Franklin Counties. 

Transitioning into the daytime hours today expect any patchy drizzle 
to come to an end as ascent further decreases and some mixing of the 
boundary layer ensues. High temperatures this afternoon will hinge 
on the depth of mixing through the day. At this point have went with 
a model average for highs with temperatures ranging from the low 50s 
along the NE border to the upper 50s along and south of I-70. If 
trends of latest RAP/HRRR come to fruition with stratus lifting 
above 2kft and mixing heights reaching 900 mb, low 60s would be 
possible. Given the expansive stratus shield extending to the TX/OK 
border and continue moisture advection, tending to think mixing 
heights will be closer to 925 mb and keep temperatures in the 50s. 

Low stratus is expected to persist through the night tonight with 
patchy fog and drizzle possible. Temperatures will are expected to 
remain steady through the night with lows ranging from the low 40s 
in North-Central KS to the low 50s in East-Central KS. The current 
forecast low of 44F and 50F at Topeka and Concordia respectively 
would set records for the "warmest low temperature" on February 3rd 
at each site. Records: Topeka (43F in 2012) and Concordia (42F in 
1992).

.LONG TERM...(Sunday through Friday)
Issued at 517 AM CST Sat Feb 2 2019

For Sunday models continue to show a low level warm air advection
pattern with some isentropic upglide over northeast and east
central KS. Because of this have maintained a slight chance for
measuring a hundredth of an inch through the day Sunday. Otherwise
the main question is whether the stratus will remain solid across
the area. The NAM shows little chance of the stratus mixing out,
but the GFS hints at the possibility over parts of north central
KS. Think the warm air advection will be good enough to help highs
into the lower and middle 60s for most areas. If the sun breaks
out, highs may make a run at the upper 60s. 

A shortwave is progged to move through the central plains Sunday 
night. All of the guidance seems to be coming in line with the
wave passing mainly north of the forecast area with the surface
low tracking along the NEB/KS state line. With the better forcing
focused to the north, chances for measurable precip look to be to
low to mention in the forecast. 

Lows Monday morning could be tricky as models show a cold front
passing through the region by noon. In general think temps on
Monday will not see much of a diurnal trend as cold air advection
increases through the day with highs occurring in the morning
before the front passes through. Dry air moving south with the
surface ridge should bring an end to precip chances through Monday
night.

Things could get a little messy for Tuesday through Thursday as
models prog a shallow Canadian airmass setting up over the 
forecast area while 850MB winds become more southerly with 
increasing saturation. Large scale forcing looks to be lacking 
until Wednesday night and models do not have much in the way of 
QPF for Tuesday and Wednesday. But there is some agreement in a 
strong warm nose advecting as far north as northern KS while temps
remain around freezing or cooler. With a reasonable signal from 
the models for freezing rain, have included a mention for it in 
the forecast. The main uncertainty continues to center around the
timing of the upper wave on Thursday. The ECMWF and Canadian 
remain fairly progressive, keeping the wave phased with the 
northern stream. Meanwhile the GFS wants to lag energy over the 
southwest, finally lifting it across the region Friday morning. 
With the ECMWF and Canadian showing pretty good consistency with a
progressive solution, think that is the more likely outcome, but 
have held onto some token chance POPs for Thursday night and 
Friday morning to account for the GFS solution. At this time, the 
expectation is for increasing POPs into Wednesday night with a 
wintry mix, including freezing rain, probable across some part of 
the forecast area. I anticipate a strong cold front to push 
through during the day Thursday changing the precip type over to 
snow. Then depending on the timing of the system, precip ending by
Thursday evening or some light snow persisting into the morning 
Friday. Adjustments to this forecast will likely be needed as it 
gets closer in time. 

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 539 AM CST Sat Feb 2 2019

Dense fog continues to overspread the area from south to north.
LIFR vsby have already arrived at the Topeka sites and expect IFR
to LIFR vsby to arrive at MHK within 1-2 hours. VSBY and cigs
are likely to improve after 15Z with MVFR conditions likely by
19-20Z. Southerly winds are likely to remain 10-15 kt through the
remainder of the period. Uncertainty arises for the late 
afternoon into the early evening as some short term solutions have
a brief period of VFR returning at all sites. Given the large 
swath of stratus across the Central US, would tend to think MVFR 
cigs should prevail through the remainder of the period. 

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon CST today for KSZ008>010-020>024-
026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Baerg
LONG TERM...Wolters
AVIATION...Baerg