Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 242313

Area Forecast Discussion
National Weather Service Norman OK
613 PM CDT Sat Mar 24 2018



For the 00z TAFs:

Some MVFR stratus could develop toward sunrise at northwestern TAF
sites (WWR/CSM) and persist through at least the morning as
southeasterly flow strengthens and greater moisture moves
northwest into the area. Further east across central Oklahoma, the
same is expected, although onset of MVFR conditions may be midday
or early afternoon. A capping warm layer aloft should suppress
showers and storms, although mid-level moistening may be
sufficient near the Kansas border for some showers at/near PNC in
the morning through midday period. Probabilities elsewhere are too
low to mention, except we did retain the PROB30 at SPS for a
conditional threat of elevated convection very late tonight.


.PREV DISCUSSION... /issued 355 PM CDT Sat Mar 24 2018/

Primary forecast issues are the chances of rain and potential for
severe weather this week.

For tonight, a subtle shortwave trough/lobe of vertical vorticity
will approach from the southwest. As this wave approaches,
isentropic ascent may result in some elevated showers and
thunderstorms across western north Texas and far southern Oklahoma
early tomorrow morning. Elevated instability and vertical wind
shear will be favorable for some small hail.

As this wave departs, a dry line is forecast to sharpen across
southwest Oklahoma, southward into western north Texas tomorrow
afternoon. A dry line bulge may develop across western north Texas
in association with a 700 mb wind maxima.

The uncertainty is if there will be sufficient ascent to weaken
the cap for convective iniation in the afternoon. The 24/12Z GFS
is aggressive in convection when compared to other parameterized
and convecting-allowing models. The GFS seems overdone based on no
appreciable ascent to lift the cap. So for now, will only have a
slight chance (20%) of showers/storms. If thunderstorms develop,
supercells will be possible with effective bulk shear >40 knots
and MLCAPE of at least 1000-2000 J/kg.

By Sunday evening into Sunday night, another shortwave trough/lobe
of vertical vorticity may approach and increase the chance of
showers/storms through the overnight hours.

By Monday and especially Monday night, widespread showers and
thunderstorms are expected to develop with increasing meridional
flow and persistent isentropic ascent as the mid/upper-level low
from the southwest U.S approaches the Southern Plains.

Initial thunderstorms on Monday afternoon/evening could be severe
as as there will be sufficient instability and vertical shear.
These thunderstorms may initially develop along a dry line across
western north Texas, northward into southwest Oklahoma. These
thunderstorm may grow upscale into an MCS into the evening hours
as they move northeastward.

Heavy rainfall will become a threat Monday night into Tuesday with
the potential of training thunderstorms--especially across the
southeast where the duration of event will be longer; however,
there has not been any recent rainfall across southeast Oklahoma
over the last 5 days. In addition, the 3-hour RFC Flash Flood
Guidance has 3-4" across most the area. Therefore, even though
localized flooding will be possible, widespread flooding is not
expected at this time.

As a shortwave trough passes by the northern Plains, the attendant
cold front will pass by on Tuesday. This should gradually shift
the moisture/rainfall to the southeast on Tuesday, decreasing the
chance of rain by Tuesday night into Wednesday. Another shortwave
(this time from the northwest), may result a low chance of
showers on Thursday.

Abundant cloud cover, precipitation, and a post-frontal air mass
will result in cool temperatures Tuesday through at least
Thursday. High temperatures should be below average in this



Oklahoma City OK  73  47  66  62 /   0  10  20  30
Hobart OK         76  51  75  63 /   0  20  20  30
Wichita Falls TX  80  56  86  66 /   0  30  20  30
Gage OK           73  46  74  55 /   0   0  10  10
Ponca City OK     68  39  60  56 /   0   0  20  40
Durant OK         81  54  73  63 /   0  10  30  20




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