Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 311748
AREA FORECAST DISCUSSION
National Weather Service Topeka KS
1248 PM CDT TUE MAY 31 2016
...Update to aviation forecast discussion...
.SHORT TERM...(Today and Tonight)
Issued at 342 AM CDT TUE MAY 31 2016
08Z water vapor imagery shows a closed upper low moving into the
Dakotas as a lead shortwave lifts through MN. Another upper lows was
noted along the AZ and Mexico border. Profiler data continues to
show weak mid level flow over the central plains. At the surface,
low pressure was seen on the ND/MN state line with a weak frontal
boundary extending south through eastern NEB and northwest KS.
Outflow from the thunderstorms across central KS have raced out
ahead of the updrafts and there doesn`t appear to be enough
convergence along the boundary to sustain new updrafts. So it looks
like showers and storms may not reach eastern KS this morning.
However the outflow is likely to stall out somewhere across eastern
KS and the models show the frontal boundary remaining nearly
stationary through the day. Therefore with some instability
developing this afternoon, these weak features are expected to act
as focus for new thunderstorm development today since there remains
little inhibition for convection. The high resolution models break
out convection by the early afternoon over northeast and east
central KS. have continued with some likely POPs through the
afternoon as the coverage from the high resolution models do not
support increasing POPs. Deep layer shear remains marginal but the
main question is how much instability may develop. Models want to
hold onto cloud cover through the morning and hold temps in the 70s.
This would suggest CAPE values would only be on the order of 1500 to
2000 J/kg. But if the sun breaks out, there could be some locations
reach 80 and may allow for some pulse type strong storms through the
afternoon. Generally have highs in the mid to upper 70s based on
forecast soundings mixing the boundary layer to 875MB.
For tonight, the models gradually build surface ridging into
northern KS with the deeper moisture axis sifting to the south.
Additionally the atmosphere should begin to stabilize due to the
loss of heating. So without any strong forcing, afternoon
thunderstorms may just fall apart during the early evening. Have
held onto some likely POPs this evening across east central KS as
this is where afternoon activity is most likely along the outflow.
Then POPs diminish through the overnight expecting activity to
dwindle with the loss of heating. Lows are expected to fall into the
mid 50s across northern KS where some weak cold air advection may
combine with clearing skies to help temps fall a little more. Lows
are forecast to remain in the lower 60s for east central KS where
there may be more cloud cover and not much if any cold air
.LONG TERM...(Wednesday through Monday)
Issued at 342 AM CDT TUE MAY 31 2016
Wednesday late morning into the afternoon will see an end to what
precipitation is left over northeastern KS. Northern stream flow
will be well off to the North through the Northern Plains into the
Upper Mid-West into the Great Lakes region as the trough lifts
into Southern Canada. Dry advection into the region will take
place and subsidence should be the rule as the upper flow suggests
weak ridging advects overhead while a modified Canadian surface
ridge extends into the region. Temps should be in the upper 70s to
around 80 with mid 50 degree dew points which shouldn`t feel too
bad for the first week of June.
The next very small chance of precipitation and the only real next
chance for precipitation at least into early next week will be
Friday evening into the Saturday morning time frame. A broad high
amplitude ridge builds over the Western CONUS while Pacific moisture
rides around the apex of the ridge sending a weak baroclinic wave
into the Upper Mid-West and Western Great Lakes region. Perhaps
enough weak ascent will extend into portions of northeastern KS to
bring a brief period of precipitation chances as steeper mid level
lapse rates associated with the weak shortwave ride over mid 60s
dewpoints in northeastern KS. The GFS is the more bullish of the
long range guidance and typically has been over doing moisture
content. However, have kept with the slight chance POP idea since
moisture arrives with the Pacific system and richer moisture won`t
have far to return ahead of the incoming shortwave that is progged
well with both GFS and ECMWF minus small differences in the two.
All in all, low 80s for high temps and low temps around 60 won`t
make for a bad beginning to the second week of June.
.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1244 PM CDT TUE MAY 31 2016
VFR conditions are expected throughout the evening and overnight
hours. Short-term guidance continues to lessen the chance for
showers and thunderstorms at the terminals this afternoon/evening,
therefore have removed any mention of RA or TS. Clearing skies
overnight should allow for ground fog to form across the area,
have introduced 5 mile visibility at TOP and MHK from 10Z to 13Z.
As confidence increases in exact timing of clearing skies,
visibilities will be adjusted accordingly.