219 
FXUS63 KTOP 010919
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
319 AM CST Fri Feb 1 2019

.SHORT TERM...(Today and tonight)
Issued at 319 AM CST Fri Feb 1 2019

As of 09Z Friday morning the low- level stratus that had 
overspread much of east-central KS has cleared the area. A 
midlevel speed max shunted a weak boundary, most notable at 850 
mb, through the area earlier this evening, progressing the stratus
just south of the forecast area. Some patchy fog is possible, 
especially along and southeast of I-35, where the status recently 
cleared. Water vapor reveals a weak midlevel low across southern 
AZ. The expectation is the low will weaken with its eastward 
progression across the Southern Plains later today, although 
sufficient PVA should allow for deepening of lee trough across the
High Plains. As a result an additional surge of low- level 
moisture is expected this evening into tonight. In-fact, satellite
and surface observations reveal this moisture surge currently 
advancing northward across Central OK. Prior to its arrival a 
pleasant day is anticipated across the CWA with plentiful 
sunshine, light winds and temperatures nearing 50 this afternoon. 

Transitioning into this evening and tonight, the aforementioned low-
level moisture is likely to begin overspreading the area after 
sunset. WAA aided isentropic ascent is progged to increase after 06Z 
with the strengthening of the LLJ to 30-40 kts. The combination of 
increasing low-level ascent and moisture would expect drizzle to 
overspread portions of the area. At this point, the southeastern 
half of the CWA appears most likely to receive drizzle, where low-
level moisture is progged to be the deepest. In addition to the 
drizzle, expect fog to develop across the entire forecast area 
tonight. Where drizzle doesn't develop, some dense fog is possible 
with visibilities less than a mile. In regards to temperatures, 
values will cool into the 30s area-wide this evening before slowly 
rising overnight into the upper 30s and 40s by sunrise Saturday.

.LONG TERM...(Saturday through Thursday)
Issued at 319 AM CST Fri Feb 1 2019

For Saturday through Sunday, models are in reasonable agreement 
with mid level ridging moving from the Rockies into the central
and northern plains with a shortwave trapped under the ridge. The
model consensus is for this initial wave to remain mainly south 
of the forecast area as it opens up and weakens while moving 
across the southern plains. However the pattern favors a 
strengthening lee trough and persistent southerly low level flow. 
This is expected to maintain a low level warm air advection 
pattern with some isentropic upglide over parts of the forecast 
area through the weekend. NAM and GFS forecast soundings continue 
to show a favorable set up for drizzle with week lift in a 
saturated stable layer. So have continued a mention of drizzle and
fog in the forecast for parts of northeast and east central KS. 
The better chances look to be during the late night and early 
morning hours. The warm air advection is also expected to push 
high temps into the 50s for Saturday and lower 60s for Sunday. 
This is in line with prev forecasts. 

For Sunday night and Monday morning, models indicate a better
defined shortwave lifting across the central plains. The NAM
appears to be more amplified with the wave, and as a result 
further south with the track of a surface low. The majority of 
the guidance generally tracks the surface low along the NEB/KS 
state line with the mid level dry slot over much of the forecast 
area. So think the better chances for measurable precip will be
north of the forecast area, along and north of the surface low
track. The wave should bring a cold front through the area by
Monday morning. Increasing cold air advection through the day is
expected to cause temps to fall through the afternoon. 

Uncertainty increases for Tuesday through Thursday as
southwesterly flow is progged to set up before a third wave moves 
through the plains late in the forecast period. The GFS shows a 
slower progression with split flow developing by Thursday evening,
while the ECMWF and Canadian maintain a more progressive phased 
solution. This has implications on location of the stronger 
forcing and timing the next Canadian high pressure system to move 
south. For now the forecast is a blend of the models with a lean
towards the ECMWF. There are some low confidence POPs in the
forecast for Tuesday and again on Wednesday. This looks to be 
derived from return flow setting up over shallow high pressure. 
Unfortunately the GFS and ECMWF disagree on the strength of this 
return flow and whether precip develops. The better chances for 
precip look to be Thursday morning when the front potentially 
moves through. Based on spread in the ensemble members from the 
ECMWF and GFS, I'd expect adjustments to the timing of the frontal
passage as well as precip chances. Also will need to watch out 
for the potential of some mixed precip with the GFS maintaining a 
warm nose behind the initial surge of cold air. Again confidence 
in any one solution is fairly low at this time. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1128 PM CST Thu Jan 31 2019

High MVFR/low VFR stratus currently along and east of the Kansas
Turnpike should gradually push east tonight, with additional MVFR
to IFR stratus surging northward over the entire forecast area 
late Friday afternoon and evening. Patchy fog will also be 
possible Friday night. Winds will remain light from the south.


&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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