Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Topeka Kansas
1158 PM CDT Fri Aug 22 2014

..update to aviation forecast discussion...

Short term...(this evening through saturday)
issued at 301 PM CDT Friday Aug 22 2014

An upper level trough over southern Arizona will lift northeast into
eastern Colorado by Saturday afternoon. A more amplified upper level
trough across eastern Washington and eastern or will dig southeast into
western Wyoming and western Colorado by Saturday afternoon. The amplified upper
level trough across Wyoming and Colorado will cause the down stream upper level
ridge axis to amplify across the mid MS River Valley during the day
on Saturday.

This afternoon there were two separate outflow boundaries located
across the County Warning Area. One outflow boundary extended from near Minneapolis,
northeast towards Hiawatha. A second outflow boundary was located
from south of Abilene and extended east-southeast to south of
Emporia, then east-northeast across southwest Anderson County to
west of Garnett. Isolated to scattered thunderstorms have been
developing all afternoon along these surface boundaries. A few of
these storms may be strong with the potential for 50 miles per hour wind gusts
and small hail. Locally heavy rainfall may also occur with these
thunderstorms. These thunderstorms should dissipate towards sunset.
As the Lee surface low deepens across northeast Colorado and northwest Kansas
tonight, the stronger isentropic lift will shift northward across
central NE. Thunderstorms should form well north and west of the County Warning Area
after midnight. Southwesterly flow aloft on the western edge of the
500 mb ridge axis will keep any thunderstorms that form on the High
Plains this evening, well west and north of the County Warning Area through the
early morning hours of Saturday.

Saturday looks dry. The 500 mb ridge axis across the MS River Valley
will amplify and the western periphery of the ridge axis will expand
west across eastern Kansas. Afternoon thunderstorms that develop across
western Kansas and eastern Colorado will move north into central NE. High
temperatures will warm into the mid to upper 90s with some 100
degree readings possible across the area tomorrow afternoon. The
operational models show deeper mixing and the deeper 850mb moisture
advecting farther northeast of the County Warning Area across northern MO and Iowa.
Thus, heat indices may only range from 100 to 104 degrees. However,
the models have been mixing out dewpoints into the mid 60s the past
couple days, even though surface dewpoints have remained in the
upper 60s to lower 70s. Therefore, I have decided to keep the heat
advisory in effect through Saturday.

Long term...(saturday night through friday)
issued at 301 PM CDT Friday Aug 22 2014

By Sunday morning the upper ridge amplifies over the eastern US
while a strong upper low lifts over the northern plains. At the
surface the boundary that has been quasi-stationary across the
region will slowly migrate eastward as those upper level systems
advance. This will leave a slight chance for storms in the
northern counties on Sunday morning. Models are suggesting weak
shortwaves within the southwest flow may move over the region
enhancing the large scale lift over the boundary. One is possible
Sunday night into Monday morning and more likely to affect the
northern counties again. The longwave trough is then forecast to exit
The Rockies around mid-week bringing better chances for precip as
the front gets driven further to the south. At the moment the
European model (ecmwf) disagrees with the GFS and Gem on the how this system will
approach the area. A majority of the GFS ensembles agree with the
operational run, which suggests the quicker solution, and the
front clearing the area by Wednesday night. The European model (ecmwf) wants to cut
off the southern trough causing it to slowly drift towards eastern
Kansas. This would delay the front and precip later into the week.
Therefore have gone with the GFS solution only keeping slight pops
in on Thursday in case the scenario European model (ecmwf) plays out. The
temperatures will continue to stay warm with afternoon heat
indices in the low 100s through Tuesday. Cooler air is forecast to
move southward behind the departing wave and surface cold front.
Temperatures during this period could be slightly below normal the
end of next week.


Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1133 PM CDT Friday Aug 22 2014

Confidence remains too low to insert any showers/thunder into
the taf fcsts since coverage of any additional convection through
12z is expected to be isolated and mainly to the north. Will only
carry sct mid and high clouds thru the fcst. Light southeast winds
through 12z will become southerly and increase beyond 14z with
gusts around 20kts...decreasing again aft 01z/23.


Top watches/warnings/advisories...
heat advisory from 1 PM to 8 PM CDT Saturday for ksz008>012-



Short term...gargan
long term...Sanders

National Weather Service Glossary of Abbreviations