Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 282344

Area Forecast Discussion
National Weather Service Norman OK
644 PM CDT WED SEP 28 2016

2900/2924 TAFS...
VFR conditions and a north to northeast wind will prevail.


.PREV DISCUSSION... /issued 231 PM CDT WED SEP 28 2016/

Water vapor imagery shows the center of a closed mid-upper low
drifting south across northwest Indiana early this afternoon. This
has forced another surge of a cooler air into our area. The cold
front is seen in surface observations nearing the Red River as of
early afternoon. Cooler temperatures and stronger north-
northeasterly winds are present behind the front.

Mid-upper ridging will be in place for the rest of the week and then
gradually deamplify this weekend. Weak shortwaves in increasingly
zonal flow may bring some mid to high clouds over the weekend.
A relatively dry post frontal air mass and meager instability
should limit convection although isolated convection may move into
northwest Oklahoma Saturday evening.

There are important synoptic scale differences in the medium range
guidance with regard to sensible weather early next week and the
potential for severe thunderstorms. GFS deterministic has not been
consistent over the last several runs with handling the western
trough and after a southward shift in the 06z run, the 12z run is
now further north once again with the closed low. This falls near
the middle of its ensemble members which are spread significantly.
By late Tuesday, GFS ensembles range from a more progressive
shortwave in the upper Midwest, to a deeper closed low positioned
over the central High Plains, to a positively tilted trough over
California. There is evidence of similar spread in the European
ensembles given the substantially less amplified broader
appearance to the trough in the 500 mb 00z European ensemble
mean. The 12z deterministic European continues to show a closed
low moving from the central Rockies into the northern Plains, with
a significant negatively tilted shortwave rotating around the
upper low crossing our area late Tuesday.

Several of the possible scenarios indicated in the medium range
guidance would support favorable veering profile and large scale
ascent for severe thunderstorms. However, even if the worst case
scenario with regard to the trough amplitude and timing were to
occur, thermodynamics may be marginally supportive of severe
thunderstorms. The lingering cut off low in the east and
associated cold intrusions in the gulf would not be particularly
favorable for robust moisture surge northward ahead of the
approaching system. However, reservoir of residual deep moisture
is expected to linger across the western gulf region. A
stronger/deeper and slower synoptic wave with longer duration and
more dramatic low level response would stand a better chance of
bringing a more significant low level moisture surge and higher
instability. Even without this, sufficient low level moisture and
heating may contribute to at least weak instability. Confidence in
the forecast next week is below average given the model



Oklahoma City OK  53  72  50  75 /   0   0   0   0
Hobart OK         53  73  49  74 /   0   0   0   0
Wichita Falls TX  56  75  51  77 /   0   0   0   0
Gage OK           48  74  47  76 /   0   0   0   0
Ponca City OK     47  71  49  74 /   0   0   0   0
Durant OK         54  76  52  79 /   0   0   0   0


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