One more warm day, then the bottom falls out….again. The sunshine and gusty southerly winds of today have produced some wildfire issues this afternoon. Those southerly winds will be even stronger for Thursday, but humidity levels will also be higher along with a low stratus deck for much of the day. That should mitigate the fire danger despite very mild temperatures for this time of year. The morning low will be near 50 which is warmer than our normal daytime high and afternoon temperatures will be well into the 60s.
Enjoy because much colder air will be arriving early Friday morning and will stay with us through the coming weekend. Although this cold front will not be as strong as the one we experienced earlier in the month, the shallow nature of the cold air is still creating a very difficult forecast problem. We will have shallow, cold air in place at the surface for Friday into the day Saturday and at the same time, warm and moist air aloft will be spreading over the colder surface air. This creates a real problem regarding just how cold and how deep those lowest levels will be as that will determine our precipitation type.
As is often the case, the guidance continues to be all over the place in that regard but has been trending somewhat warmer. The actual storm center is still located out in the Pacific so it still has not been well sampled by our observational network. So, here is my best shot with the current set of data and keep in mind this is certainly subject to change.
Temperatures should be falling to near the freezing mark Friday morning, particularly for N and W of the I-44 corridor. At the same time there will be a slight chance of some very light drizzle just about anywhere so that could result in some slick spots for elevated surfaces during the morning hours of Friday. Keep in mind some of the guidance keeps temperatures well above freezing throughout the day, so this is basically a potential worst case scenario.
The main event will be starting during the overnight hours of Friday night and through Saturday when rain will be more widespread. At the same time, temperatures along and NW of the I-44 corridor may be near the freezing mark so there will again be the potential for some slick spots on elevated surfaces. As the day wears on, our winds will become more E and even SE for the more southern counties with quite a temperature contrast across the state. 50s and even some 60s will be possible along and south of I-40 where some locally heavy t'storms will be possible. Elsewhere, temperatures will moderate well above freezing so a cold rain for the more northern counties. This looks to be a very wet system as the QPF map on the right clearly shows. In fact, there may be some flooding issues for the more SE counties and also the possibility of severe weather during the day Saturday.
Colder air at the surface and aloft will then be returning Saturday night and Sunday morning as the main storm system quickly moves overhead and on eastward. That will provide an opportunity for the rain to change to snow. This should be a quick moving system but for locations NW of I-44 there may be a quick 1-2" before it comes to and end mid-day Sunday.
After that, looks rather quiet going into Christmas Day itself. So, stay tuned and check back for updates.