Area Forecast Discussion
Issued by NWS Topeka, KS
Issued by NWS Topeka, KS
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
641 FXUS63 KTOP 160734 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 234 AM CDT Mon Sep 16 2024 .KEY MESSAGES... - Above normal temperatures are forecast to persist through the workweek. - There is a 30 to 60 percent chance of showers and thunderstorms Wednesday morning. - Better chances (around 60 percent) for widespread rain and storms are forecast Friday night through Saturday night. && .DISCUSSION... Issued at 234 AM CDT Mon Sep 16 2024 07Z water vapor imagery showed a weak upper low over the lower MS river valley with a closed low over northern CA. This left weak ridging from the southern Rockies into the middle MO river valley and a generally confluent pattern over northeast KS. Surface obs showed low pressure along the lee of the Rockies with high pressure east of the MS river. This has allowed southerly low level flow to persist. There are not a lot of changes to the forecast. Models show a weakly forced pattern remaining over the forecast area through Tuesday with POPs mainly driven by some mid level warm air advection and isentropic lift. This lift is progged to be strongest during the morning hours today and Tuesday. But elevated instability remains modest and bulk shear looks to be weak, around 20KT. Overall CAMs have backed off on developing elevated showers and storms this morning and especially Tuesday when the HREF has probabilities around 10 to 20 percent. Have kept some small POPs through the late morning today with some convection already occurring to the west. But followed the NBM and lowered POPs for Tuesday morning. With the forcing remaining rather subtle the next few days, confidence in the POP forecast will remain on the low side. The overall ideas from the deterministic solutions are pretty much unchanged through the end of the week and into the weekend. A shortwave trough lifting into the northern plains Tuesday night could clip north central KS with showers and storms Wednesday morning. The better dynamics look to lift north but most guidance is developing some QPF over north central KS. Because of this POPs from the NBM have trended higher with likely chances across north central KS. Don`t think 60 percent chances are unreasonable, but the lack of synoptic scale forcing and lift brings into question the coverage of precip Wednesday. Models show a better organized upper wave lifting through northwest KS over the weekend. While the trend has been to slow the progression of the upper wave, there is not a lot of disagreement from the operational solutions. And ensemble data from the ECMWF and GFS continue to show high probabilities, 80 percent or greater, of measurable precip on Saturday. The NBM appears to be catching up with this idea and now has 50 to 70 percent chance POPs for late Friday through Saturday night. So there is increasing confidence in precipitation chances this weekend, and I wouldn`t be surprised if POPs trend higher in the coming days. The pattern through the workweek supports southerly low level winds and continued warm air advection. This should keep temperatures above normal with highs in the middle 80s to around 90. The warmest day looks to be Thursday as models strengthen southwesterly flow in the wake of the initial shortwave. Highs could end up in the lower to middle 90s on Thursday. Rain chances and increased cloud cover are expected to keep temperatures cooler for the weekend. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1204 AM CDT Mon Sep 16 2024 Models keep the mid level isentropic lift to the west and north of the terminals. So the main concern is whether any ground fog develops. RAP forecast soundings keep some wind in the boundary layer with cross over temps below the forecast lows. Additionally some think high clouds may move in from the west. So will keep a VFR forecast and monitor trends through the morning. If fog was to form, it would be brief and around sunrise. && .TOP WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Wolters AVIATION...Wolters