Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 132246

Area Forecast Discussion
National Weather Service Topeka KS
546 PM CDT Tue Mar 13 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday)
Issued at 340 PM CDT Tue Mar 13 2018

Little sensible weather is forecast for tonight and tomorrow with
the biggest challenges of the forecast revolving around
temperature trends.

A strong upper level omega block was anchored over the Rockies
early this afternoon in water vapor imagery with a 1033 mb surface
high pressure cell building southward into the Central Plains.
This setup will bring clear skies for tonight as the high moves
overhead. A dry tongue was associated with this ridge, with
dewpoints falling into the single digits above/below 0 F from
Salina northward into Central Nebraska. Leveraged the recent HRRR
runs to model this wedge of dry air for tonight and early tomorrow
as most guidance was far too moist. The combination of clear
skies, light winds, the very dry air, and little soil moisture
will cause temperatures to plummet tonight into the 20s and even
upper teens. Went close to the MET guidance for lows, with a
similar setup last week resulting in lows that were 5+ degrees
cooler than most solutions.

Wednesday will feature clear skies and increasing SW winds as the
surface high departs and the surface pressure gradient over the
state increases. There is some concern that the wedge of dry air
may linger through part of the day before increasing moisture
overspreads the region. Warmer downslope air overspreads the
region on Wednesday, allowing highs to surge into the upper 60s to
low 70s in most locations. The combination of increasing/gusty
winds and low RH values will present a widespread very high fire
danger day throughout NE Kansas.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 340 PM CDT Tue Mar 13 2018

The chance of precipitation creeps back into the forecast for late
in the week with temperatures at or above normal--the exception
possibly being Friday.

Thursday will be a near carbon-copy of Wednesday temperature-wise
with H850 temps in the +8 to +10 C range and surface temps in the
70s. Some locations in central Kansas could push the upper 70s
closer to the H850 thermal ridge. The surface flow turns slightly
more to the south, advecting increasing amounts of moisture into
the region and reducing the fire weather risk. A baroclinic zone
develops over the state during the course of the day as lee
cyclogenesis takes place over the Front Range in response to an
approaching H500 vort max. Winds on Thu night into Friday look to
remain on the strong side given the 20-40 ubar/km pressure
gradient over the region. NAM/GFS forecast soundings show a
shallow mixed BL throughout the night with winds of 15 to 25 kts
throughout this layer.

Increasing 295-305 K isentropic upglide over the effective lower
tropospheric warm front will fuel elevated showers and possibly a
few thunderstorms over NE Kansas overnight Thu/early Fri morning.
However, forecast soundings and MUCAPE plots are rather unimpressive
and only kept slight chance of thunder mentioned in the forecast.
Recent runs of the EC/GFS have come into some agreement in the
position of the warm front for Friday--bisecting the CWA from NW
to SE. Highs therefore on Friday could vary greatly between the
upper 40s on the KS/NE border to the upper 60s by Emporia. The dry
slot punches northward over the CWA by midday Friday, likely
bringing an end to any widespread precip. A light drizzle is
possible north of the warm front Friday night into Saturday
morning before the low pulls out. While it is quite a ways out to
nail down any top-down forecast parameters, the current synoptic
setup would support a small window of freezing drizzle near the
KS/NE border early Saturday morning. Did mention this possibility
in the grids but it is of very low confidence at the present time.

After the departure of this system on Saturday morning, an active
zonal flow pattern will set up for the weekend and early next week.
However, confidence in the timing and locations of these late period
systems is low. The next decent chance of precip after Sat morning
possibly arrives Sun night.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 545 PM CDT Tue Mar 13 2018

VFR conditions are forecast to persist through the period with
light winds overnight becoming southwest with some gusts after 15Z


Issued at 340 PM CDT Tue Mar 13 2018

Northerly winds today lessen tonight and then switch to the SW by
sunrise on Wednesday. These winds increase to between 10 and 15
mph with gusts near 25 mph at times on Wednesday. Dry air
currently in place over the state slowly moistens during the day
on Wednesday, but widespread very high fire danger conditions are
still forecast during the day. Currently forecast RH/wind
conditions are straddling the extreme fire danger category for
Wednesday and there is a chance that, should conditions
deteriorate any further, that a Red Flag Warning may be issued.

For Thursday, southerly winds lessen slightly and RH values will
also be somewhat higher, limiting the areal extent of the very
high fire danger threat to along and west of the Flint Hills in
the afternoon.




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