Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 291140
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
640 AM CDT Sun Mar 29 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 407 AM CDT SUN MAR 29 2015

At 3 AM, a strong short wave trough was crossing the Dakotas and
Nebraska with the main vort max moving quickly southeast in central
South Dakota. A strong front was associated with this system, and
extended from northeast Nebraska into northwest Kansas...quickly
progressing southeast. North of (behind) this front, temperatures
were actually much warmer...in the upper 50s to lower 60s with gusty
northwest winds. Immediately in advance of the trough, enhanced
mid-level moisture and forcing for ascent, along with weak elevated
convective instability, were supporting scattered sprinkles and rain
showers. There is plenty of dry air to overcome for any precip to
reach the ground though, so have kept any precip chances quite low
with a mention of sprinkles or light rain showers through mid
morning. The surface front is expected to reach Concordia by 8 AM,
Manhattan around 9 AM, Topeka before 11, and Garnett by 1 PM. As the
front passes, northwest winds will increase sharply with gusts to 30
mph or stronger. The strongest gusts, perhaps in excess of 40 mph
are expected across northern KS with even stronger winds in
Nebraska. Temperatures may also quickly warm immediately behind the
front for an hour or two before returning to a more typical diurnal
temperature trend. A 1-2 hour period of lower RH in the 20-30% range
is expected right after frontal passage before actually increasing a
bit...and then decreasing once again from mid through late
afternoon. The MinRH is expected to range from around 20% in north
central KS to near 30% in far eastern KS, and will combine with the
strong winds, wind shift, and dry fuels to produce very high to
extreme fire danger. Winds fall below 10 mph after sunset with
increasing RH overnight. Clear skies and nearly calm winds after
midnight should allow low temperatures to fall into the middle 30s
with lower temps possible in valleys.

.LONG TERM...(Monday through Saturday)
Issued at 407 AM CDT SUN MAR 29 2015

Quiet and mild weather is expected for the early half of this week
as northwest-to-southeast oriented mid-level zonal flow sets up over
the central U.S.  At the surface, high pressure advances into the
southeastern U.S. with low pressure across the High Plains,
resulting in southwesterly surface winds. A decent pressure gradient
should set up over the area on Monday, resulting in good warm-air
advection from the breezy southwesterly winds and high temperatures
surging into the low/mid 70s. The warmest temperatures look to be
across north central Kansas where a nose of 12C-16C 850mb
temperatures should be present with model soundings suggesting
decent afternoon mixing. In addition to breezy winds, conditions
should be fairly dry with RH values dropping into the low to mid 20
percent range by Monday afternoon, resulting in very high fire
danger concerns for the entire CWA. A weak boundary should advance into
the area Tuesday morning, however it looks to become washed out
over the area and do not anticipate any precipitation. There
should be just enough mixing on Tuesday to help boost temperatures
a few degrees warmer than Monday with highs in the mid/upper 70s.

Models continue to stay in pretty good agreement with the timing and
tracking of the next system into the area. A mid-level trough looks
to move into the Pacific Northwest Tuesday night and track eastward
into the Northern Plains by Thursday. This advancing trough will
push an area of surface low pressure into the central U.S. on
Wednesday with models still showing the associated cold front moving
into north central Kansas by late afternoon to early evening and
tracking southeastward across the CWA through the overnight hours.
As a result, have likely PoPs for most of the CWA on Wednesday
night. While models continue to show upwards of 1000-2000 J/kg of
MUCAPE with decent enough bulk shear in place, soundings suggest
that there may only be a small window of time in which storms may be
surface-based before they become elevated as temperatures begin to
quickly fall during the evening hours. As a result, we will need to
continue to monitor this set-up and the potential for a few strong
storms. Model discrepancies begin to appear with regards to how
quickly this cold front exits the CWA, with the GFS being the most
progressive while both the GEM/ECMWF are slower in having the front
exit by mid to late Thursday morning. As a result, confidence is low
for Thursday PoPs as the GFS has us dry while the ECMWF/GEM keep
lingering showers and thunderstorms across east central Kansas.
Another area of uncertainty is with the next mid-level trough that
is progged to advance into the central U.S. Thursday night into
Friday. The ECMWF is stronger and a bit deeper with this trough in
comparison to the GFS, and thus shows a better potential for showers
and isolated thunderstorms Thursday night into Friday. In contrast,
the GFS keeps the region dry behind Wednesday night`s frontal
passage. In addition to low confidence in the PoPs for late this
week, confidence is also low in temperatures due to the variances in
the strength of the next trough. In general, the models are showing
a cool-down behind the front with the coolest day being Friday and
Friday night with highs in the 50s and possibly low 60s and lows
dropping into the 30s. Have a dry forecast for Friday night through
Saturday as GFS/ECMWF both show surface high pressure advancing into
the area. As surface winds shift to the southwest on Saturday,
temperatures should start rebounding back into the 60s.

&&

.AVIATION...(For the 12Z TAFs through 12Z Monday Morning)
Issued at 619 AM CDT SUN MAR 29 2015

VFR conditions are likely through the TAF period. A few showers
are possible through 14Z, but should be mainly dry. Winds near
1200 ft AGL are at 50-55 kts according to nearby wind profiler
data, and 50 kts closer to 2000 feet AGL via TOP RAOB, so have
kept LLWS in the TAF through around 14Z. A front with strong
northwest winds will arrive at all TAF sites between 14Z and 16Z
with winds calming down near 01Z.

&&

.FIRE WEATHER...
Issued at 407 AM CDT SUN MAR 29 2015

Have issued a Red Flag Warning for parts of the area while the
remainder of the forecast area can expect very high fire danger. The
main fire issue today will be a very strong front and incoming dry
air through the day. The front is expected to reach Concordia by 8
AM, Manhattan around 9 AM, Topeka before 11, and Garnett by 1 PM. As
the front passes, northwest winds will increase sharply with gusts
to 30 mph or stronger. The strongest gusts, perhaps in excess of 40
mph are expected across northern KS with even stronger winds in
Nebraska. Temperatures may also quickly warm immediately behind the
front for an hour or two before returning to a more typical diurnal
temperature trend. A 1-2 hour period of lower RH in the 20-30% range
is expected right after frontal passage before actually increasing a
bit...and then decreasing once again from mid through late
afternoon. Between the two periods of lower RH, the MinRH for the
day is expected to range from around 20% in north central KS to near
30% in far eastern KS, and will combine with the strong winds, wind
shift, and dry fuels to produce very high to extreme fire danger.
Even areas without the red flag warning would be considered
borderline for issuance, but held off at this time as RH values in
eastern KS look to be a bit higher in the middle/upper 20s and winds
just a bit lighter (still gusty) as you go farther southeast. Winds
fall below 10 mph after sunset and become nearly calm by midnight as
an inversion builds overhead, with increasing RH after 8 PM.

Very high fire danger concerns are in place for the entire outlook
area on Monday as temperatures warm up into the 70s, southwesterly
winds become breezy with gusts upwards of 25 to 30 mph during the
afternoon, and RH values drop into the low to mid 20 percent
range.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING from 11 AM this morning to 7 PM CDT this
evening FOR KSZ008-020-021-034-035.

&&

$$

SHORT TERM...Barjenbruch
LONG TERM...Hennecke
AVIATION...Barjenbruch
FIRE WEATHER...Barjenbruch/Hennecke





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