Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 280818
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
318 AM CDT Tue Oct 28 2014
.SHORT TERM...(Today and Tonight)
Issued at 228 AM CDT TUE OCT 28 2014
Recent water vapor satellite imagery depicts a strong upper wave
rotating through the main upper trough across northern Kansas. A few
bands of mainly weak radar returns have passed through much of the
local area in recent hours via rather strong upper level
frontogenesis, but quite dry low levels limiting this to very light
amounts (if any) reaching the ground. NAM and RAP indicate both
forcing and moisture aloft diminishing through sunrise and these
processes seem to be underway per latest IR and radar trends.
Surface high pressure was building into the central High Plains with
temps there around the freezing mark under mainly clear skies and
light winds. It appears radar-produced low-level winds are being
impacted by bird migration with speeds likely 10-20kt too high.
Cold air advection becomes rather modest today, but much cooler air
than recent days will keep highs in the lower to mid 60s in decent
mixing. There should be a second round of high cloud in the morning
to early afternoon, but the late afternoon and nighttime hours
should be clear as the surface high comes into the Central Plains.
Expect some modification of the upstream airmass today, where local
temps have been well above normal for several days. Lows will be
kept above freezing, with slightly lower values likely in protected
areas. Have boosted frost wording but rather dry airmass and the
very warm ground may keep widespread frost in check.
.LONG TERM...(Wednesday through Monday)
Issued at 228 AM CDT TUE OCT 28 2014
A cool start expected for Wednesday with morning frost possible
across much of the forecast area. Temperatures still should make
it to lower to middle 60s as southerly winds slowly move into the
area from the west on the back side of the surface high. Some
amplified mixing and southerly flow comes through with the clipper
along and just to our north early Thursday, bringing mixed
overnight low temperatures in the 40s. Despite cooler air moving
driving southward into the northern and central plains for
Thursday, our area is on the leading edge of the colder air and
should mix to another day in the 60s before the colder
temperatures make it southward.
Again incoming high pressure and northerly winds through the night
Thursday night into Friday look to keep lows from tanking too far,
but do have lows in the 30s north to near 40 south. Sunshine
should help get temperatures into the 50s for Friday afternoon.
The surface high moves into the upper Midwest late Friday into
early Saturday, and keeps push of colder air over eastern Kansas
with lows forecast in the 30s. Another quick return of an upper
ridge and southerly surface winds should bring highs back into the
50s for Saturday.
How the next round of upper trofs moves out of the Rockies for
Sunday into Monday varies within the extended models. Could see
some warm air advection showers early Sunday but chances too low
for mention this early. Both EC and GFS suggest better chances for
rain come later Sunday into Monday and will keep grids as such,
but smaller scale and progressive nature of the waves will likely
change timing and probabilities as forecast draws closer.
.AVIATION...(For the 06Z TAFs through 06Z Tuesday Night)
Issued at 1120 PM CDT MON OCT 27 2014
VFR prevails as northwesterly winds back to the west and weaken
through 17Z. BKN cloud cover gradually exits east as influence from
surface high pressure spreads eastward. Another passing upper wave
increase westerly winds to near 10 kts during the afternoon with
SCT high clouds in place.