Area Forecast Discussion
Issued by NWS Topeka, KS

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851
FXUS63 KTOP 161736
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1236 PM CDT Sat May 16 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 346 AM CDT SAT MAY 16 2015

A broad upper level low was located across NV, UT and AZ early this
morning. A 65KT mid level jet max was lifting northeast across
eastern NM into western KS. The strong ascent ahead of this jet max
has helped to develop a line of showers and thunderstorms from
central NE, south-southwest into west TX. Most numerical models show
this line weakening as it moves east into a more stable airmass
across eastern KS through the morning hours.

A stronger H5 trough located along the southern base of the upper
level low will lift northeast across eastern NM into the northern TX
PNHDL through the late morning hours. Several numerical models all
show an area of scattered to numerous thunderstorms developing ahead
of a surface dryline across the eastern TX PNHDL through the mid
and late morning hours. These storms lift northeast and intensify
through the early and mid afternoon hours, as they move northeast
across western OK into south central KS. The 5Z HRRR shows this area
of thunderstorms moving northeast into the western counties of the
CWA by 20Z. Most numerical models show the atmosphere destabilizing
early this afternoon across the CWA, after the weaker storms from
this morning dissipate or lift off to the northeast. the WRF runs,
NAM and HRRR show SBCAPE of 2500 to 3500 J/KG. The 0-1KM shear looks
fairly weak with most models forecasting less than 100m2/s2 of 0-1KM
SRH. SFC to 6KM effective shear will be increasing to 40 to 60 KTS
during the afternoon. Therefore, the environment will be favorable
for severe thunderstorms this afternoon. Another question will be
the mode of convection. If a complex of storms develops across
northwest OK late this morning and maintains itself northeast
across the CWA than any tornado threat will be quite low. Though
stronger updrafts within a QLCS or complex of thunderstorms would
produce large hail and damaging wind gusts. The HRRR and NAM 4KM
simulated reflectivity forecast more scattered to isolated
thunderstorms developing across north central OK and south central
KS early this afternoon, and moving northeast into the southwest
and southern counties of the CWA after 22Z. I suppose if we see
discrete supercells than there will be a chance for tornadoes
along with the large hail and damaging wind gusts.

Late this afternoon most models show thunderstorms developing along
the Pacific front/dryline across west central KS and western OK. The
environment will really improve ahead of the dryline late this
afternoon, with much stronger low-level vertical wind shear. Any
discrete supercells that develop along the Pacific front/dryline
across west central KS and western OK will have a chance to produce
tornadoes. Through the evening hours these discrete to scattered
supercell thunderstorms may congeal into line segments or a QLCS and
move northeast into the western counties of the CWA during the mid
evening hours. If discrete supercells move into the western counties
this evening, then there will be a chance for tornadoes. I suppose
if a QLCS develops there is a potential for meso-vortices tornadoes.

Cloud cover will probably keep high temperatures in the mid to
upper 70s.

Tonight, The upper low and lead H5 trough will lift northeast into
southwest NE. Line segments of thunderstorms or a QLCS will move
east across the remainder of the CWA during the late evening hours
into the early morning hours of Sunday. The primary hazard will be
large hail, damaging winds and heavy rainfall.

.LONG TERM...(Sunday through Friday)
Issued at 346 AM CDT SAT MAY 16 2015

On Sunday the dry slot will work across the area with lower
dewpoints but daytime highs should still reach to around 80 given
mixing and expected sun. The cold front will finally move across
the area Sunday night and it should pass through dry however there
are some signals that precip may develop along it toward Mon
morning southeast of the area. For now will keep conds dry and
with CAA on Monday expect much cooler highs and lower humidities
as dewpoints fall into the 40s. Tues should also remain dry for
most of the day with rain expected to overspread the area Tues
night and last through Weds. Limited CAPE suggests only isolated
thunder but look for another widespread soaking rain out of this
system.

Perhaps a brief dry spell on Thursday before the next upper wave
approaches for late next week into next weekend. This system looks
very similar to this weekends so an active pattern will continue.

&&

.AVIATION...(For the 18Z TAFs through 18Z Sunday Afternoon)
Issued at 1234 PM CDT SAT MAY 16 2015

Sites have cleared to VFR after a line of showers moved through the
area this morning.  VFR should continue until a line of storms moves
from SW to NE this afternoon into tonight impacting all terminals.  Exact
timing and coverage of these storms is still uncertain, and have
continued to use VCTS for this reason.  Storms will clear overnight
into tomorrow morning from W to E. After this clearing VFR will
prevail.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Gargan
LONG TERM...Omitt
AVIATION...Heller






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