Area Forecast Discussion


091 
FXUS64 KOUN 212143
AFDOUN
Area Forecast Discussion
National Weather Service Norman OK
343 PM CST Wed Feb 21 2018
.DISCUSSION...
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 
the 60Fs.
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.
Mahale
&&
.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 
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Winter Weather Advisory until 9 AM CST Thursday for OKZ004>048-
     050>052.
TX...Winter Weather Advisory until 9 AM CST Thursday for TXZ083>090.
&&
$$
26/10