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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

                            
000
FXUS63 KTOP 192035
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
335 PM CDT Mon Aug 19 2019

.SHORT TERM...(This evening through Tuesday)
Issued at 333 PM CDT Mon Aug 19 2019

A broad 500mb ridge centered over the Southern Plains has slowly 
built in this afternoon as skies have turned mostly clear, 
allowing for conditions to heat up with surface temps in the low 
90s and dew points in the mid to upper 70s. This ridge will 
strengthen during the overnight period into Tuesday, bringing the 
heat further north and expanding it across the entire CWA. 
Overnight lows will only fall back to the mid 70s, allowing us to 
warm up more quickly during the afternoon. By that time models are
bringing 850mb temperatures in the 24-27C range, which translates
to highs in the 90s area-wide, possibly near 100 toward central 
KS where heat indices may approach 110 degrees for an hour or two.
The potential exists to upgrade the Heat Advisory to a warning 
for tomorrow, but given low confidence related to 
overnight/morning convection in IA and MO, will maintain the Heat 
Advisory across the CWA at this time.

The main uncertainty in the temperature forecast for Tuesday is 
related to an MCS that is progged to develop in eastern NE/western
IA overnight and progress southeastward into MO by the morning 
hours. The vast majority of the models have kept precip out of our
area as the better mid to upper level forcing is to our north and
east, but the GFS solution clips northeast KS with this complex, 
so have maintained slight chance PoPs overnight into early Tuesday
morning to account for that possibility. An outflow boundary from
that system could then keep temperatures slightly lower, 
particularly in eastern KS. Regardless, we will still be hot and 
humid with heat index values in the 100-110 degree range. Any 
precipitation as a result of the boundary should hold off until 
late Tuesday into Wednesday, but will continue monitoring the 
trends as we move forward.


.LONG TERM...(Tuesday night through Monday)
Issued at 333 PM CDT Mon Aug 19 2019

The middle to latter half of the week looks to resume an active, 
wet pattern, with confidence steadily decreasing in convective 
evolution and timing the further one travels into the future.

Broad west to northwest zonal flow will remain in place into the 
weekend with multiple weak perturbations working through the flow 
during this timeframe. As is the case with this pattern, each 
round of convection will influence the next round of convective 
behavior. Starting Tuesday night, there are some indications on 
the longer range CAMs that the remnant outflow boundary from the 
Monday night/Tuesday morning MCS could still be lingering across 
the northeast portions of the forecast area, potentially 
reinforcing the near-surface synoptic warm front already along the
KS/NE border. Steep mid-level lapse rates would promote 3000-5000
J/kg of ML/MUCAPE into the evening, but also result in a H850 
warm nose that would need substantial modification to support 
convective initiation. There exists a lack of any notable synoptic
lift to cool this warm nose, which when combined with the wide 
range of model QPF solutions, does not add much confidence in the 
development of thunderstorms. The more likely solution is that 
convection develops over Nebraska, closer to the H850 front and 
upper level support, and then builds southeastward along its cold 
pool into northern Kansas Wednesday morning. 

A low-amplitude trough translating eastward under the base of a 
slow- moving northern North America omega ridge approaches the 
Front Range Wednesday evening, which will promote more widespread 
convection along the effective frontal boundary somewhere in 
southern Nebraska and northern Kansas. Heavy rainfall will be a 
concern with this event given the slow-moving, training nature of 
the complex and an environment primed with warm cloud depths 
exceeding 4 km, PWATS of 2+ inches, and ample low-level moisture 
transport northward from the Gulf. However, confidence in the axis
of heavier rain is low at the present time. Storms may linger 
through Thursday depending on the progression of the H300 trough, 
with a lull in the activity possibly on Friday. For the weekend, 
confidence steadily decreases in the timing of any convection and 
have maintained just slight chance PoPs in the forecast.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1224 PM CDT Mon Aug 19 2019

VFR conditions are expected to continue this afternoon and evening
as skies remain clear aside from a few high clouds early. Have
introduced LLWS at 06Z through the overnight hours due to a
35-40kt LLJ developing during this time period. Confidence of 
storms reaching the terminals tomorrow morning remains too low to 
mention in the TAFs as better chances are to our north and east.


&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for KSZ021>024-026-
034>040-054>056-058-059.

Heat Advisory from noon to 9 PM CDT Tuesday for KSZ008>012-
020>024-026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Picha/Skow
LONG TERM...Skow
AVIATION...Picha/Skow