FXUS64 KOUN 212143
Area Forecast Discussion
National Weather Service Norman OK
343 PM CST Wed Feb 21 2018
Persistent southwest flow aloft will keep the southern Plains
within an unsettled weather pattern through Saturday with periods
of precipitation expected.
For this afternoon/evening, a wintry mix of sleet and freezing
rain will continue to shift east-northeastward. As this
precipitation moves out this evening, forecast soundings suggest
areas of freezing drizzle will be possible into the overnight
hours. NAM soundings suggest a saturated layer from the surface to
~800 mb. NAM isentropic chart at ~295K indicates low-level ascent
as well. There is even a signal in the HRRR and HRRRX of some
light echoes. The 4 KM NAM is even more aggressive than the
HRRR/HRRRX. So in addition to freezing drizzle, light freezing
rain could also be possible.
Based on the aforementioned analysis, freezing drizzle was added
to the forecast for tonight. With the potential for freezing
drizzle, opted to expand the Winter Weather Advisory through 9 AM.
Freezing drizzle is more efficient at accretion, so travel
impacts would occur in areas that experience it.
Another round of precipitation is expected mid-Thursday morning
into Thursday afternoon. All model guidance suggests temperatures
will warm above freezing tomorrow; however, confidence is not high
as guidance has been too warm with this air mass. In addition,
surface winds are expected to remain northerly through mid-morning
(which isn't favorable for temperatures to warm above freezing).
Forecast NAM soundings have temperatures right around 33-34F in
central Oklahoma during onset of precipitation. Opted to trend
toward the NAM solution (with temperatures warming only slightly
above freezing in the afternoon) and also added a mention of
freezing rain (along with rain) into the afternoon hours.
Confidence is not enough to extend a Winter Weather Advisory
beyond 9 AM--but the trend will to be monitored carefully.
Yet another round of precipitation is expected Friday afternoon
into Saturday. Confidence is higher that temperatures will be
above freezing with this round of precipitation. Elevated
instability begins to increase as well, so thunderstorms will be
possible. Warmer, above average temperatures are expected by
Saturday afternoon. Many locations may have high temperatures in
By late Saturday, a cold front is expected to pass by the area.
This should bring an end to the unsettled pattern. The air mass
behind this front appears to be from downslope flow, so it does
not appear to be that cold. As a matter of fact, no significant
temperature change is expected for Sunday. Quiet, seasonable
weather is expected in the front's wake on Sunday and Monday.
More unsettled weather may return by Tuesday and Wednesday of
next week as southwest flow returns with a longwave trough across
western United States. Isentropic ascent ahead of the wave will
increase the chance of precipitation. At this time, temperatures
appear to be too warm for winter precipitation.
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 23 34 32 52 / 40 60 0 40
Hobart OK 23 35 30 51 / 20 40 0 30
Wichita Falls TX 27 35 33 49 / 20 60 0 60
Gage OK 21 35 30 54 / 20 20 0 0
Ponca City OK 27 35 31 51 / 50 50 0 20
Durant OK 32 39 39 53 / 60 80 40 80
OK...Winter Weather Advisory until 9 AM CST Thursday for OKZ004>048-
TX...Winter Weather Advisory until 9 AM CST Thursday for TXZ083>090.