Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 210222
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
922 PM CDT Fri Apr 20 2018

.UPDATE...
Decreased the chance of rain for this evening across central
Oklahoma.

&&

.DISCUSSION...
Numerous showers and isolated thunderstorms continue across
northwest Oklahoma this evening. These showers/storms appear to be
associated with a lead shortwave trough/vort max that will
continue to lift north-northeastward. This will initially prevent
much eastward progress of the rain. Therefore, the chance of
showers/storms was decreased markedly for this evening across
central Oklahoma.

Behind this lead wave, the primary wave will approach the
Southern Plains. As this happens later tonight, a low-level jet
and attendant isentropic ascent will result in widespread rain to
develop (which will facilitate the eastward shift of rain). The
greatest ascent appears to be across south central into central
Oklahoma by late tonight into Saturday morning. where there is
essentially a 100% chance of rain.

Mahale

&&

.PREV DISCUSSION... /issued 625 PM CDT Fri Apr 20 2018/

AVIATION...
21/00Z TAFs. VFR conditions expected to prevail majority of area
through 06Z before conditions deteriorate with incoming RA/TSRA.
As upper storm system moves over the region, cigs will fall and by
12Z and beyond, widespread IFR conditions are expected both during
and after the heavier rain activity moves east. Added TSRA to all
sites given potential for at least embedded TSRA but impacts
should be brief at any terminal.

PREV DISCUSSION... /issued 344 PM CDT Fri Apr 20 2018/

DISCUSSION...
Showers and a few thunderstorms are just west of our forecast
area as of 3:30 pm, and the area of rain will continue to move
northeast this afternoon and into the evening. Short-range models
consistently show another band of rain that will form ahead of
this one later this evening, possibly bringing rain into central
Oklahoma a couple of hours before midnight.

Showers and a few thunderstorms are forecast to increase in
coverage through Saturday, before the system begins to move away
to the east Saturday night and Sunday.

Surface-based instability will be generally lacking, and most-
unstable CAPE values will be too low to support anything beyond
isolated marginally severe storms. In short, severe storms are
unlikely in our forecast area through the event.

As this system departs, northwest flow aloft will become
established. This is typically a dry pattern in winter, but we
will have at least a chance of showers and thunderstorms with a
couple of fronts that move into Oklahoma/north Texas. The first
is expected on Tuesday, and the second one late in the week,
probably Friday. Again, severe weather is relatively unlikely with
both fronts.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  49  56  45  62 /  80 100  60  10
Hobart OK         50  57  44  66 /  80  90  20   0
Wichita Falls TX  52  59  45  67 /  80  80  20   0
Gage OK           47  53  41  64 /  90  60  20   0
Ponca City OK     47  54  45  62 /  80  90  60  10
Durant OK         50  58  50  65 /  30  90  70  10

&&

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

$$

10/11


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