Dangerous Wind Chill Through Monday Afternoon

Second Arctic Blast Coming **
Interesting to note Lawton reached 80 degrees Sunday, just one degree shy of the record and ranks #9 (3 way tie) in the top 10 warmest December days ever for Lawton, according to "NOWDATA" on http://www.weather.gov/. OKC was two degrees shy of the daily record of 74 set in 1933.It was no surprise when the arctic front arrived a few hours before model forecasts. This is a typical bias. Models never do a good job on handling the extremes of cold arctic air, and as a result, I would not be surprised to see a high temperature bust tomorrow. I have already dropped highs below the coldest guidance, which comes from the Weather Central Adonis model. I'm going 23 for OKC and upper teens NW OK. I referenced Dodge City, Wichita and OUN guidance before laying down the final numbers for Monday. See graphics at http://www.okcfox.com/ for details. First round of precip brought a little light snow to northern OK, and some freezing rain to northeast OK as indicated by 35 dbz echos and lightning strikes. Appears Enid and points east may have picked up a little bit of freezing rain in the transition, and some light sleet has been reported in central and north central OK as well.Northern OK should be cloudy much of Monday where highs will remain in the 10s. Comparing WRF-ARW wind grids and high temperatures, I calculated wind chill values between 8 and 14 degrees with current expected highs. Highs might be a bit too generous too as mentioned. It appears much of central and eastern Arkansas all the way to Memphis may get a round of sleet and ice today while we were spared.Our two locally run models, ADONIS and WRF-ARW are in excellent agreement in generating an area of snow across extreme northwest OK, mainly in Woods/Ellis/Harper/Woodward counties overnight Monday night into Tuesday. New 0Z run only has snow in Harper and Woods counties and WRF and GFS are even further north. The southern end of this band may be accompanied by some sleet according to BUFKIT soundings from WRF-NMM. I used it's temperatures heavily in the first 3 day forecast. I see OUN has done the same. ADONIS actually has a better handle on days 1 & 2 it appears and is colder. I was thinking there could be some sleet in central OK with the passage of a wave across KS on Tuesday, but latest model runs are suggesting it all the precip may be confined to snow in eastern Oklahoma Tuesday afternoon. I am dropping pops on Tuesday to 20%. Cloud cover should hold highs in the 10s and 20s. I have 27 for OKC (from National run of ADONIS) and think that may be too high.Many models have a huge problem with arctic outbreaks and want to bring warm fronts back north through Oklahoma within a couple of days of the arctic outbreak. We are seeing that bias with the ECMWF and GFS and to some extent with the new NAM run. I have seen many, many forecast busts where the model wants to bring the warm front up past the red river and warm us up. The new guidance is a complete joke. Here's the models and their numbers. You'll see the ADONIS is the only one with a clue.GFS 29, Tues: 19/40, Wed: 34/58NAM 29, Tues: 15/36, Wed: 29/48NGM 27, Tues: 17/39, Wed: 35ADONIS: 22, Tues: 10/24, Wed: 18BUFKIT from WRF-NMM was actually good on the 12z run and has a high of 27 Tuesday. Winds appear way too light to do much good. A weak front should drop south out of Kansas on Tuesday evening and arrive in OKC around 6 pm. On Wednesday, I was tempted to remove pops completely but dropped them down to 30%. New WRF-NMM has precip across NW OK Wednesday evening but I think this is part of the aforementioned warm frontal bias so I am discounting it. The fact the models are clueless for this time period makes forecasting it even more difficult. It does look cloudy though.The long and short of it is that all POPS for OKC should be close to zero, at least until the shortwave ejects out Thursday across NW OK and Kansas. Even that day may be questionable if all the energy passes across NW OK. GFS has finally gotten a clue with this run and has created a frontal system to eject out with the storm system on Thursday. It's timing is in question. It is interesting to note that ECMWF has had this front in the last 3 days runs yet all the other local forecasters seem to be ignoring it. GFS didn't even have it until this 0Z run, and again, appears to be too fast with it.ECMWF has the front going through on Friday around 3 am. The south wind ahead of the system, combined with overrunning precipitation, should eventually warm things up above freezing and cause a change over from freezing precip to rain Thursday. I disagree with the GFS's positioning of the warm front in southern Kansas. It will likely be near the Red River (again, the model not handling arctic air well).Once the Thursday front passes, north winds take over. Using snow accumulation modeling from Earl Barker's website I noted significant snowpack across central and northern Kansas. North winds will be blowing over this snowpack into Oklahoma and therefore, I have gone below all forecasters on temperatures Friday. Even if the warm front did make it to southern Kansas, it would still not make it past the snowpack so it will still be on the ground.Once this system.passes, another reforms right behind it back in the western OK panhandle. This one will pull another surger of arctic air down with it on Saturday, just in time for the weekend. Next weekend looks brutally cold and quite similar to the situation we are having now.
OKC 16/23 12/27 22/29 23/38 29/33 25/25 15/24 11/27 24/35
more at http://www.okcfox.com/
Greg Whitworth, Fox 25 Weather