087 
FXUS63 KTOP 040920
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
320 AM CST Mon Feb 4 2019

.SHORT TERM...(Today and tonight)
Issued at 320 AM CST Mon Feb 4 2019

As of 09Z Monday morning a strong cold front was bisecting the 
CWA from southwest to northeast. Temperatures ahead of the front 
remain in the 50s to near 60, whereas strong CAA behind the front 
has dipped temperatures into the 20s across Northern KS. Low-level
stratus extends approximately 175 miles northwest of the front in
portions of Southern NE. The overall motion of the of front is 
southeast at ~25 kts. As a result, expect a 6-7 hour residence 
time for stratus at any one location this morning with mostly 
sunny skies thereafter. Northwesterly winds will remain strong 
behind the front with sustained speeds 15-25 MPH, gusting upwards 
of 35 MPH. Winds will gradually decrease by late morning into 
afternoon as a surface ridge axis overspread the area, weakening 
the LLJ and surface pressure gradient. Temperatures will only 
moderate a few degrees this afternoon with highs ranging from the 
lower 30s near the NE border to near 40 south of I-70.

Transitioning into tonight, the aforementioned surface ridge will 
slowly progress eastward with the forecast area remaining on the 
southern periphery of the ridge. This should maintain a surface CAA 
pattern with easterly winds area-wide. Low temperatures are progged 
to range from the lower teens along the NE border to the middle 20s 
in East-Central KS. An upper low currently positioned off the 
Pacific Northwest Coast will dive southward into CA through the day 
today. A weak, lead-shortwave trough is likely to eject across the 
Central High Plains tonight, in turn, deepening the lee trough 
across High Plains. As a result, expect another round of 850 mb WAA 
late tonight into Tuesday. The strongest WAA and associated 
saturation is progged to overspread the area generally after 12Z 
Tuesday, therefore do not have any mention of precip prior to 12Z.

.LONG TERM...(Tuesday through Sunday)
Issued at 320 AM CST Mon Feb 4 2019

The main forecast concern for Tuesday through Wednesday night 
will be centered on temperatures and the implication for precip 
type. Models are in reasonable agreement with the overall synoptic
pattern as southwesterly flow aloft on Tuesday sees a high 
amplitude trough move across the central plains by Thursday. 
Surface ridging that builds into the central plains today is 
likely to remain over at least part of the forecast area through 
Wednesday night. Meanwhile southwesterly 850MB flow is progged to 
advect warm and moist air north over the shallow surface ridge 
leading to the potential for some light precip. 

In spite of the general agreement in the synoptic pattern, there
are some differences in the details among the models. The NAM 
looks to be deeper and further south with the base of the upper 
trough. And the GFS develops a surface low further north over 
west central KS and lifts the warm sector further north than any
of the other models. So the question is whether the NAM, with a
strong surface ridge and cold temps is correct, or the GFS that 
lifts the warm sector into northeast KS is correct. The general 
consensus is the GFS is to far north with the surface low and 
warm sector. The ECMWF seems to offer a good compromise with a 
more likely track to the surface low but weakens the surface ridge
enough to allow temps to warm above freezing across east central 
KS on Wednesday. 

With forecast soundings showing stratus redeveloping as warm air
advects over the shallow surface ridge, there could be some
drizzle on Tuesday. Temps look to range from the mid 20s to the
mid 30s Tuesday and Tuesday night. So there is some potential for
light ice accumulations if drizzle actually develops. Precip
amounts look to be on the order of a few hundredths of an inch. By
Wednesday and Wednesday night, the approaching upper trough is
likely to bring some dynamics into the area. Although the system
overall does not look that strong with an open positively tilted
wave passing overhead and the better forcing passing to the north
of the forecast area. Another problem is the model consensus 
continues to show a mid level dry slot advecting over northeast KS
through Wednesday night. So ice in the clouds continues to look
questionable until the strong arctic airmass moves in Wednesday 
night and cools low levels into the -12C range. Have the better 
chances for precip Wednesday night, which looks to be a wintry mix
of freezing rain, sleet and maybe some snow. Unless models shift
the storm system, precip amounts look to remain light with the 
mid level dry slot over much of the area. At this point, it looks 
like there could be some ice amounts up to a tenth of an inch with
maybe a dusting of snow across north central and northeast KS. 
Based on NAM and GFS forecast soundings, think any convective 
potential is fairly small across east central KS to include a 
mention of thunder at this time. There certainly are some steep 
lapse rates forecast from the models, but the low level warm nose 
looks to create a strong inversion to a surface parcel. Also any 
elevated instability looks to be pretty shallow before running 
into additional inversions. If the GFS turns out to be correct in 
lifting the warm front into northern KS, there may end up being a 
greater potential for thunder on Wednesday. 

Precip is expected to come to an end Thursday morning as much 
dryer air moves in and the upper trough axis shifts to the east. 
The surface ridge should bring dry weather to the area through 
Saturday with cold temps likely Thursday and Friday. Some 
moderation looks to occur Saturday as southerly return flow 
develops ahead of the next upper trough which is expected to move
into the plains on Sunday. This will be the next chance for some
rain and snow. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1111 PM CST Sun Feb 3 2019

MVFR stratus is once again developing and lifting northeast,
impacting KTOP and KFOE through 10Z. VAD wind profiles are picking
up on 60 kts plus at around 1500 feet so have kept the mention of
LLWS through 11Z. A cold front is forecast to reach KMHK between
09Z-10Z and KTOP/KFOE from 10Z-11Z. IFR to LIFR stratus is
observed behind the boundary as strong northwest winds gust to 30
kts through the morning. Drier air behind the boundary is 
expected to scatter out low stratus to VFR before 17Z.

&&

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

$$

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