Area Forecast Discussion
Issued by NWS Tulsa, OK

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FXUS64 KTSA 181531

Area Forecast Discussion
National Weather Service Tulsa OK
1031 AM CDT Mon Sep 18 2017

Scattered showers and possibly a few thunderstorms will
continue to be possible into mid-afternoon across eastern
Oklahoma and western Arkansas as a mid-level shortwave
moves across the region. Have lowered temperatures for
this afternoon a degree or so across northeast Oklahoma
and western arkansas with the lingering cloud cover.


.PREV DISCUSSION... /Issued 634 AM CDT Mon Sep 18 2017/

Weakening MCS continues to diminish in areal coverage as it moves
into eastern Oklahoma this morning. Will include VCSH for the OK
TAFs for the first few morning hours. Precipitation chances will
be ending from west to east by midday, with broken high clouds
scattering out by this evening.

PREV DISCUSSION... /Issued 310 AM CDT Mon Sep 18 2017/


The main forecast challenge will be rain/tstorm chances/severity
in the short term. Precip chances next weekend and into early next
week are another item worth noting. An extended period of above
average temps is expected throughout this forecast.

A shortwave trough, embedded within the subtropical jet across
the southern tier of states, was passing by the Four Corners
region and was moving quickly east. An area of scattered storms
was ongoing over the TX/OK Panhandles ahead of this feature. Another
smaller scale feature, or lead impulse, is likely driving the
southern OK MCS.

Let`s address the short term convective trends. Current hi-res
model data indicates that the S OK complex should gradually
weaken with time as it moves into eastern OK this morning. The
latest mesoanalysis from SPC shows considerably weaker instability
over eastern OK compared to central/western OK, so this idea
seems reasonable. The activity over the panhandles will likely do
the same. There is indication that new development could occur
ahead of the wave near and north of the KS border later this
morning however. The morning PoPs and QPF will attempt to capture
the short term convective trends. The lift from the wave should be
exiting quickly to the east by 18Z, so only low PoPs will be
maintained in the east after 18Z. Cloud cover across the north is
expected to hold temps back a bit for today.

A dry forecast can be expected in the wake of the shortwave
trough for the upcoming week. The subtropical jet is expected to
weaken and shift south of our area while the polar jet carves out
a deep trough over the western CONUS. As a result, the subtropical
moisture flow that has brought storms to the region of late will
be cut off. Highs will return to the 90s Tuesday and Wednesday for
most area, with a gradual cooling trend toward the end of the week
as the low level thermal ridge contracts back to the west in a
more amplified flow pattern.

The 00Z runs of the ECMWF and GFS continue to slow down the
eastward progress of the western CONUS trough and associated front
late next week. As such, PoPs have been removed for most of the
weekend, ramping them up quickly as we head toward the beginning
of the next work week.





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