Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 180822

Area Forecast Discussion
National Weather Service Topeka KS
322 AM CDT Sun Mar 18 2018

.SHORT TERM...(Today and tonight)
Issued at 320 AM CDT Sun Mar 18 2018

A few forecast highlights to mention in the next 24 hours as a
poignant system translates over the region. Low level stratus
associated with the departing sfc ridge to our east has bisected
CWA, creating a 10 degree gradient in temperatures this morning.
Clear skies over north central and portions of east central Kansas
combined with the light east winds may result in patchy dense fog
this morning. A few of the high resolution models are hinting at
more widespread dense fog after 10Z so will need to monitor obs
for the possibility of an advisory.

For today, skies remain mostly cloudy in approach of the lead
shortwave trough lifting northeast into southern Kansas by late
afternoon. Lowered highs today by a few degrees into the low and
middle 50s due to the likelihood of cloud cover holding across far
northeast and east central areas during the afternoon. Moisture
return appears to be lagging further south with confirmation from
short term guidance until after sunset so there is some
uncertainty on how quickly saturation occurs and rain showers
develop over southern Kansas. As lee cyclogenesis commences with
the upper low deepening over the KS and OK border during the
evening hours, strong ascent in conjunction with steepening mid
level lapse rates results in elevated CAPE at or less than 400
J/KG. Bulk shear profiles are fairly strong in the early evening
hours so cannot rule out a few elevated thunderstorms capable of
producing small hail. Otherwise the main story is the much needed
rainfall as the upper forcing maximizes as the main vorticity lobe
lifts through the region. Track of the low axis has slightly
shifted further north, with a consensus for a few heavier
downpours south of Interstate 70 after midnight when rain chances
are highest. QPF amounts by Monday morning could range between a
quarter and half of an inch with lingering rain showers.

.LONG TERM...(Monday through Saturday)
Issued at 320 AM CDT Sun Mar 18 2018

By Monday morning, the surface and mid-level lows will be tracking
eastward along the KS/OK border and advancing across Missouri
through the day.  Wrap-around precipitation looks to extend across
much of the CWA through the morning hours, bringing potentially a
few tenths of an inch of additional rainfall. Models show another
shortwave developing within this mid-level flow and tracking across
the CWA by Monday evening, so some additional light rainfall will be
possible before conditions dry out by Tuesday morning.

Behind this exiting system, models show the central U.S. remaining
under northwesterly flow aloft as mid-level troughing stays in place
across the eastern U.S. with a broad mid-level ridge over the
western U.S.  Surface high pressure will also slide into the central
U.S. Tuesday into Tuesday night before getting shunted east of the
area by the advancing mid-level ridge.  With this surface and mid-
level pattern in place, northerly winds Monday and Tuesday will keep
conditions cooler and below the seasonal normals with highs in the
mid 40s to low 50s.  Once the surface high shifts east of the area
on Wednesday, the shift to southwesterly winds will support some WAA
and boost high temperatures into the upper 50s to mid 60s.

Models show an expansive mid-level low moving into the Pacific
Northwest by Thursday and extending eastward into the Northern
Plains through Friday, causing the mid-level ridge over the central
U.S. to flatten into relatively zonal flow. This advancing mid-level
low well help to push surface low pressure over the Rockies eastward
across Kansas late week into early weekend. However, there are still
significant model discrepancies with regards to the timing,
tracking, and strength of this approaching surface low. As a result,
confidence is low with the timing and location of any precipitation
chances from Thursday night through the weekend. Despite these
discrepancies, models do at least suggest a decent pressure gradient
developing near this surface low, which will result in breezy
southerly winds supporting continued WAA into late week.  As a
result, high temperatures into the 60s and 70s will be possible
ahead of this system.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1144 PM CDT Sat Mar 17 2018

Continue to closely monitor edge of MVFR stratus, with satellite
imagery since 04Z suggesting some a northeast push. At this point
will keep MVFR cigs in place at TOP and FOE. Light winds and
increasing RH suggest at least MVFR BR possible around 12Z at MHK.
Fairly good potential for VFR conditions in the 18-22Z window
before shower chances increase with the incoming system.




LONG TERM...Hennecke
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