Area Forecast Discussion
Issued by NWS Topeka, KS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 44 45 46 47 48 49 50

000
FXUS63 KTOP 222354 AAA
AFDTOP

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TOPEKA KS
654 PM CDT Fri Aug 22 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Saturday)
Issued at 301 PM CDT FRI AUG 22 2014

An upper level trough over southern AZ will lift northeast into
eastern CO by Saturday afternoon. A more amplified upper level
trough across eastern WA and eastern OR will dig southeast into
western WY and western CO by Saturday afternoon. The amplified upper
level trough across WY and CO 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 CWA. 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 MPH 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 CO and northwest KS
tonight, the stronger isentropic lift will shift northward across
central NE. Thunderstorms should form well north and west of the CWA
after midnight. Southwesterly flow aloft on the western edge of the
H5 ridge axis will keep any thunderstorms that form on the high
plains this evening, well west and north of the CWA through the
early morning hours of Saturday.

Saturday looks dry. The H5 ridge axis across the MS river valley
will amplify and the western periphery of the ridge axis will expand
west across eastern KS. Afternoon thunderstorms that develop across
western KS and eastern CO 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 CWA across northern MO and IA.
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 FRI 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
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 ECMWF wants to cut
off the southern trough causing it to slowly drift towards eastern
KS. 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 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 00Z TAFs through 00Z Saturday Evening)
Issued at 647 PM CDT FRI AUG 22 2014

Convection in the vcnty of the KTOP/KFOE has dissipated. Confidence
is too low to add any additional convection potential near any of
the TAF sites through the remainder of the fcst. Will therefore
carry VFR conditions with sct-bkn mid and high clouds with south
to southeast winds under 10 kts increasing to around 12 kts with
gusts near 20 kts aft 14z.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY until 8 PM CDT Saturday FOR KSZ008>012-020>024-026-
034>040-054>056-058-059.

&&

$$

SHORT TERM...Gargan
LONG TERM...Sanders
AVIATION...63






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.