Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 191130
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
630 AM CDT Tue May 19 2015
...Update to aviation forecast discussion...
.SHORT TERM...(Today and Tonight)
Issued at 345 AM CDT TUE MAY 19 2015
Water vapor imagery shows the mid level low digging over the SW US
this morning. Models show this mid level low will lift northeastward
over NE and SD tonight, and become more of an open wave in the
process as it interacts with a northern trough. Meanwhile at the
surface high pressure centered over the northern plains extended
southward into KS. Clear skies and light winds have supported decent
radiational cooling this morning so lows in the 40s are still on
track. As that mid level low approaches the region mid to high level
clouds will gradually build through out the day. High temperatures
today only reach the upper 50s to low 60s, and winds will be out of
the northeast generally around 10 mph. Models are hinting at a lead
shortwave ejecting over northeast KS during the afternoon hours.
This mid level lift may be enough to produce a shower, but they will
have to overcome the low level dry air in place. The main wave lifts
just north of the area tonight and will cause the low level jet to
intensify directly overhead. A weak surface low looks to ride along
a front south of the region, while decent isentropic lift will
support more widespread precipitation during the overnight hours.
Precip will spread eastward out of western KS during the day and
should reach central KS around sunset. Instability is rather limited
therefore only mention isolated thunder at this time. Southwesterly
flow aloft and the low level jet should pump higher moisture into
the area with pwats generally around 1.3 to 1.5. The highest
moisture looks to stay located over the southern half of the
forecast area, which has already received quite a bit or rain
recently. The models continue to show conflicting QPF bulls eyes
making it difficult to pin down where the heaviest rain may fall.
This could mainly be tied to where the best focus will be associated
with the low level jet. For now have the highest values across the
southern half, and will not issue any watches at this time.
.LONG TERM...(Wednesday through Monday)
Issued at 345 AM CDT TUE MAY 19 2015
Wednesday, An upper level trough will lift northeast across the
central plains into the upper Midwest. A surface low across
southeast KS at 12Z WED will move east into southern MO through the
day. The stronger ascent will shift northeast of the CWA during the
morning hours, bringing an end to any light rain and isolated
thunderstorms by Noon. The NNM version of the WRF and the GFS show
light QPF through the day across the eastern half the CWA. Therefore
I`ll keep a slight chance for rain showers into the afternoon hour
across the eastern half of the CWA. Cloud cover and low-level CAA
will keep temperatures quite cool, with highs only reaching the mid
to upper 50s.
Wednesday night through Thursday night, expect dry conditions as a
southern stream H5 trough moves east into the the southwestern US.
An upstream H5 ridge will amplify across the southern plains. A
surface ridge of high pressure will move east across KS, then shift
east into MO late Thursday night. Highs on Thursday will continue to
be cool with mid 60s expected. The northern counties of the CWA may
see lows dip down into the upper 30s by sunrise on Thursday.
Friday through Monday, the upper trough across the southwestern US
will slowly shift east into the plains late Sunday into Monday. The
upper level trough will be filling as it moves east into the plains.
As deeper moisture returns Friday afternoon the chances for showers
and thunderstorms will increase. There will be periods of showers
and thunderstorms through the weekend. The vertical wind shear looks
rather weak for severe thunderstorms. I suppose during the afternoon
hours, if we see insolation that destabilizes the atmosphere enough,
we could see strong to marginally severe storms during the afternoon
and evening hours of Saturday and Sunday. The main hazard may be
periods of heavy rainfall Friday night through Sunday night. Highs
will warm into the lower 70s on Friday with mid to upper 70s
expected Saturday through Monday.
.AVIATION...(For the 12Z TAFs through 12Z Wednesday Morning)
Issued at 624 AM CDT TUE MAY 19 2015
VFR conditions expected through most of the daytime hours.
Confidence is increasing that widespread showers will move through
the taf sites later tonight. The chances for thunder are low
therefore did not mention in the taf, but isolated thunder can
not be ruled out. Ceilings are expected to lower to MVFR/IFR late
in the period. Timing of the onset may need a slight adjustment