Widespread travel problems, school closures expected Monday afternoon to Wednesday AM

** Freezing Drizzle, Sleet & Snow Monday through Tuesday **
** Widespread travel problems, school closures expected Monday afternoon to Wednesday AM **Sunday will be a day between weather systems. Morning cloud cover across much of central and western Oklahoma will move into eastern Oklahoma during the day. With sunshine, high temperatures should make the 40s in many areas. Some parts of southwest OK may touch 50 while northern OK may not get out of the 30s.Winds gradually veer to the northeast on Monday. Shortly after sunrise, stratus and sleet should break out across northwest and west-central Oklahoma, with snow across the Oklahoma panhandle. It is expected to become widespread quickly, as shown by our Adonis Microcast model in agreement with GFS and NAM-WRF maps. South and east of the sleet area, widespread freezing drizzle is expected. NAM-WRF grids place all areas roughly northwest of I-44 and north of Altus below freezing for the entire day. Southeast of that line, some light mix then rain should be expected.
Please refer to this website for a graphical depiction of precipitation type: http://weather.cod.edu/loops/wrfUS.preciptype.html T
his will be a prolonged event but fortunately one of light intensity. GFS and to some extent the WRF-NAM has been showing more intense uplift and higher Omega fields on Tuesday. This should lead to slightly heavier precipitation. 0Z NAM suggests the precip types will slide southeast Tuesday morning, with snow in northwest OK and sleet near I-44 and freezing drizzle across much of southeast OK and northern Arkansas.GFS historically does a better job with areal coverage of light winter precipitation of any variety, while NAM does a better job with peak intensity areas. Despite GFS's higher QPF/storm totals, I tend to believe in these types of situations the WRF-NAM will do better with peak totals given past history. Therefore, I think amounts of a quarter to half inch can be expected. This would lead to widespread travel problems, school and business closures, but minimal impacts to power lines and trees.Here are some model depictions.. first, total sleet for the event:0z/12z NAM:http://wxcaster4.com/nam/CONUS1_NAM212_SFC_ACCUM-SLEET_84HR.gif6z/18z GFS:http://wxcaster4.com/gfs/CONUS2_GFS0P5_SFC_ACCUM-SLEET_84HR.gifand here's the depiction for total freezing rain:0z/12z NAM:http://wxcaster4.com/nam/CONUS1_NAM212_SFC_ACCUM-FZRN_84HR.gif6z/18z GFS:http://wxcaster4.com/gfs/CONUS2_GFS0P5_SFC_ACCUM-FZRN_84HR.gif
The event should wind down Tuesday afternoon. Tuesday temperatures will likely not move much at all. Less than a 4 degree spread in the low and high is likely in many areas, especially southwest, central and northeast OK. The next shift will likely need to drop Tuesday a couple more degrees.GFS, NAM and old ECMWF showed a positively tilted long wave trough moving through by sunrise Wednesday. However, with the highly tilted trough, no precipitation is expected. Moisture should be robbed by the system which will be to our southeast. I suspect winds will go light southerly by day's end. ECMWF has had this trough passing Thursday morning the past two runs and has been discounted.A fairly strong front arrives Thursday morning. I have it through OKC at sunrise. It should bring strong north winds and falling temperatures. I have a suspicion by Thursday afternoon it will be in the 30s, and it may not get out of the 30s that morning, so the next shift will probably need to drop temperatures more. There is some indication in the pressure and wind fields that the cold air may be lagging behind the initial frontal passage. A second weaker long wave trough passes Thursday evening and I'm only giving it 20% pops, with 30% in northwest Oklahoma (light snow?).West winds and downsloping finally arrive Friday with a huge warm-up. I have gone above guidance on temps Thursday and Friday as history shows MOS has been under forecasting highs with such dry air in place. Granted the low levels will be slightly moister with a quarter to half inch of precipitation in the top soil, but some evaporation will have occurred with strong north winds the day before and scanty totals to begin with.Southwest wind returns on Saturday and I have kept my previous shift forecast of 63 for OKC. The past two days, GFS has erroneously left a remnant cut off low behind the long wave troughs as they passed. NWS model bias page says UKMET handles phasing of the northern and southern branches of the jet stream best. ECMWF does not have this low either so I am discarding any cloud cover or precipitation the GFS develops on Saturday, and going with a southwest wind and above guidance number temps.A front arrives Saturday evening. New GFS grids from IPS meteostar are trending to lower temperatures as I had yesterday.. looks like some 40s are in order for Sunday.Beyond the 7 Day, the GFS has been very consistent with a ridge overhead, sunshine and a south breeze for several days, with near record warmth. If this verifies and the moisture comes up, we could be looking at the first severe weather episode of the spring season around February 6th.
That's a big "if" though.OKC 23/46 27/32 25/30 24/41 34/40 21/56 30/63 32/49 30/63 34/68 41/73 50/75POPS: 80% Monday & Tuesday, 20%
ThursdayDaily cloud codes: UZXEEUUUUACA
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Greg