Area Forecast Discussion
Issued by NWS Springfield, MO

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FXUS63 KSGF 201049
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
549 AM CDT Fri Oct 20 2017

...12Z AVIATION UPDATE...

.SHORT TERM...(Today and tonight)
Issued at 230 AM CDT Fri Oct 20 2017

Passing cirrus and southerly winds were keeping temps in the
middle to upper 50s this morning. The upper level pattern was
shifting more to a southwest flow with waves of energy moving
through the southern plains. A much larger and stronger wave was
moving into the Pacific Northwest and this will be the major
player for the weekend. The airmass over our area was very dry
therefore it will be another dry and warm day today. Winds will be
on the increase as low pressure forms over the Rockies.

Moisture will continue to slowly increase tonight as a 850mb low
level jet develops mainly to our west. This combined with a weak
shortwave may trigger a few showers during the Overnight hours.
Most locations will likely stay dry. It will also be very warm and
breezy tonight.

.LONG TERM...(Saturday through Thursday)
Issued at 230 AM CDT Fri Oct 20 2017

While an isolated shower or storm cant be ruled out during the
day Saturday, it will likely be another warm and very windy day.
Wind gusts will likely reach 35mph in many locations during the
day and evening hours.

Main attention will be the severe weather potential Saturday
night:

Setup: A strong shortwave trough and associated cold front will
sweep through the area Saturday night. Plenty of forcing/lift will
be present along with a very strong (50kts) 850mb low level jet.
Adequate wind shear will be present for organized storms given
progged 0-6km shear values of 35-45kts with excellent directional
shear given surface winds out of the south to southeast.
Helicities will also be in that 150-250 range.

Limiting Factors/Uncertainty: Moisture quality and resultant
instability are still somewhat in question. Last evening soundings
still showed a dry airmass from our gulf source region as high
pressure over the southeast was keeping the low level flow out of
the northeast down there. Models do show this switching to more
of a southeast fetch over the next 24 hours. The western gulf was
recovering a little better with 60F dewpoints along that coast.
Will need to watch the recovery over the next 24 hours.

The NAM continues to be the most bullish with moisture return and
instability. It is showing between 1000-2000j/kg of CAPE across SE
Kansas into southern Missouri late Saturday night. The GFS is
generally around 750-1000j/kg. Both models however do show
weakening of instability east of US Highway 65.

Main Hazards and Timing: It still appears that a line of severe
thunderstorms will develop from Kansas City to east of Wichita in
the mid to late evening hours and roll eastward. Models generally
show the line of storms reaching the Kansas/Missouri state line
between 10pm and midnight and then reaching the US Highway 65
corridor between 12am-3am. Given the instability and wind shear
forecast, damaging winds will be the overall highest threat.
Given steep mid level lapse rates of 7.5C/Km and lowering freezing
levels (11-12KFT), cant rule out a few hail instances. Will need
to monitor any line segments that orient northwest to southeast
and/or surge to the northeast given favorable 0-3km shear. This
could result in an tornado or two along the line of thunderstorms.
This will be a mesoscale forecast challenge and will be closely
monitored. Locations along and west of US Highway 65 will have
the overall best chances of seeing severe weather late Saturday
night with storms generally weakening east of Springfield. This
matches well with the Storm Prediction Center Day 2 Outlook.

Lastly, with a strong low level jet pumping in moisture and
forecast PW values of 1.5-1.75in, there will be a limited threat
for some heavy rainfall and localized flooding. Most of the area,
with the exception of SE Kansas and portions of western Missouri,
can take 1-2 inches of moisture. Therefore we are not expecting
much flooding impacts at this time. Most places will see some
rainfall.

The shortwave trough will attempt to cut off to our south Sunday
into Monday therefore cool conditions will persist. A much
stronger upper level trough pushes through on Tuesday bringing in
a reinforcing cool blast with highs struggling to reach 60 and
lows in the 30s Wednesday morning. 850mb temps reach near 0C
Wednesday morning which signifies a strong trough passage and that
the seasons are definitely changing. Precipitation chances look
very low next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 545 AM CDT Fri Oct 20 2017

VFR conditions will be the rule with some cirrus spreading
through the area today. Southerly winds will increase and become
gusty from late morning through the rest of the day. Low level
wind shear will develop Tonight at all the TAF sites. A scattered
shower can not be ruled out Overnight however confidence is much
too low to include at this time.


&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

$$

SHORT TERM...Burchfield
LONG TERM...Burchfield
AVIATION...Burchfield



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