Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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474
FXUS64 KOUN 241502 AAA
AFDOUN

Area Forecast Discussion...UPDATED
National Weather Service Norman OK
1002 AM CDT Thu May 24 2018

.UPDATE...
Area of showers/storms that moved into SW parts of the fa earlier
this morning has been decreasing over the last hour or so. This
activity is associated with an MCV that is expected to move across
parts of the area, towards central OK, today. Another MCV from
yesterday evening/overnight convection will move along the OK/KS
border today as well. Sfc heating and the MCVs are expected to
lead to additional isolated to scattered showers/storms this
afternoon/evening. Current thoughts are that the highest chances
will be near the MCVs so chance PoPs were added along the
projected tracks of these features. However, at least a low chance
of storms will be possible anywhere in the fa due to heating. Some
of the storms could be strong this afternoon with gusty winds.
Heavy rain will also be a concern. The number of storms is
expected to decrease this evening due to the loss of heating.


&&

.PREV DISCUSSION... /issued 608 AM CDT Thu May 24 2018/

DISCUSSION...
12Z TAF discussion.

AVIATION...
Showers and thunderstorms across western Oklahoma this morning are
expected to gradually dissipate this morning, although may not
completely go away. Will keep a mention for a few hours at the
beginning of the forecast at WWR/CSM/LAW. Even with this activity,
expect mainly VFR conditions across the area. Although could see a
shower or thunderstorm just about any location later today, will
only mention a chance for late afternoon and evening activity to
impact PNC, where chance is a bit higher.

PREV DISCUSSION... /issued 309 AM CDT Thu May 24 2018/

DISCUSSION...
Minor changes were made to the short term portion of the forecast,
with little if any change in the long term portion.

An expanding cold pool from High Plains convection last evening into
our moist/conditionally unstable air mass has resulted in greater
convection coverage early this morning than expected. This should
continue to decrease into the morning. A couple of factors led us to
expand low precipitation chances southward this morning through much
of the day; 1.) residual outflow boundary that has slowed
southeastward progress and should become more diffuse with time
(albeit probably not as quickly as short term hi-res guidance
suggests suggests), and 2.) well-defined MCV moving through the
low rolling plains approaching western north Texas.

Even aside from these mesoscale features, transient PV anomaly and
broad low-level confluence in a moist and unstable environment this
afternoon should be enough for at least isolated diurnally driven
convection again. Mesoscale analysis later this morning through
early afternoon will help us better identify residual boundaries and
areas that have the greatest chance of thunderstorms, and based on
this analysis precipitation chances for portions of the area may
need to be increased. Such a moist environment and slow storm
motions could again result in locally heavy rainfall and flooding.
The severe weather threat should be tempered some at least
spatially and temporally by weak flow aloft. Single cells and
multicells could pulse to severe levels bringing brief bouts of
wind and hail.

Any expanding cold pools later this evening could keep convection
going beyond diurnal peak in instability. One possibility is for a
southward sinking outflow and/or complex of thunderstorms in Kansas
affecting north-central Oklahoma. Another is robust cold pool
development from High Plains convection once again that could drive
weakening convection eastward across western Oklahoma through the
evening and into the night.

For Friday, details become unclear. Some residual synoptic boundary
forced south by northern Plains wave could enter northern Oklahoma,
probably augmented by Kansas convection/MCS the previous night
(tonight). By then, veering mid-level winds will have advected
steeper mid-level lapse rates contributing to strong instability by
afternoon. This may also contribute to subtle increase in capping,
suppressing isolated activity across much of the area except near
aforementioned convergence boundary. Convection that occurs near
this boundary, which probably will be over northern Oklahoma,
could be quite intense with a threat of severe wind/hail
initially, followed by intense cold pool development. This is show
in some models, particularly the NAM. A forward propagating MCS
could then evolve and move south-southeast across much of the area
during the evening/overnight. Given this possibility, we have
increased precipitation probabilities Friday night for roughly
the eastern two-thirds of the area.

Some isolated diurnally driven convection could occur Saturday
morning across the southeast portion of the area, but amplifying
ridging and building mid-level heights will be working against
this.

There is not enough of a change in the synoptic scale depiction in
medium range guidance to change much in the long term, so very
little changes to the previous forecast were made from Sunday
onward. The general pattern will be for a deep closed low in the
west encouraging diurnally driven High Plains convection each day
Sunday through Tuesday, with some risk of this convection making
it to northwest portions of our area each of those evenings.
Otherwise, hot summer-like temperatures will prevail.

BRB

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  87  69  92  67 /  30  30  10  40
Hobart OK         90  69  96  67 /  30  30  20  10
Wichita Falls TX  90  70  96  69 /  20  20  10  20
Gage OK           90  67  98  64 /  30  20  20  10
Ponca City OK     88  70  93  65 /  30  30  40  50
Durant OK         89  70  91  68 /  20  20  10  30

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&

$$

25/10



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