A major and possibly historic cold front will sweep across the middle part of the nation today and enter our area this evening. This front will bring a chance for thunderstorms this evening but more importantly much colder air Thursday and Friday. Temperature records for both minimum daytime highs and daily lows will be in jeopardy across portions of the state with this system. A freeze is a possibility Friday morning across northern OK and southern Kansas. There will be several minor issues that could keep temps slightly above freezing including the potential for some cloud cover and northwest breezes.
The first issue we'll deal with is the timing of the initial front. The boundary will enter northwestern OK by midday to early afternoon and rapidly advance southeastward. Once the front encounters far Eastern OK it may briefly slow for a while, but should clear the entire state by 3am Thursday morning. Most data supports the boundary arriving across the Tulsa metro between 9pm and 10pm tonight and into the east-central OK area around 1am to 2am.
The air mass ahead of the boundary will be sufficiently warm in the mid-levels to create a capping inversion. This means the possibility of pre-frontal thunderstorms will be very low. The higher probability will be for post frontal thunderstorms (behind the front) and this will limit the severe weather threat for our immediate area to some marginally severe hail. The cold front surge will quickly undercut the updraft process for thunderstorms. This means the window for severe weather is expected to be very small and only for about an hour directly behind the boundary this evening.
Now the hard part. The temps early Thursday morning between 2am and 7am may still be in the mid-40s but some of the data is suggesting our numbers will drop into the upper 30s or lower 40s by midday to the afternoon with some showers moving across northern OK. The last few runs of the NAM suggest the air mass will be cold enough from the upper levels to lower level (just above ground) to support wintry precipitation, mainly across northwestern OK! Yes, it's very difficult to imagine some mix or snow in May, but the data output does suggest this possibility for some of our neighbors to the northwest of our area. Critical thickness values are lagging slightly behind the precip and we're highly unconfident in this portion of the forecast.
Late Thursday night into Friday morning temps could easily drop below freezing for several hours if the clouds clear and the winds decrease speeds. Again, we have one data set suggesting this possibility, while others will keep us around or slightly above freezing with some clouds. Tough call.
The main upper level low will become cut off from the flow and could linger near northern OK and southern Kansas through the early part of the weekend. This means will have a slight chance of some showers both Friday afternoon and also Saturday before the low begins to move away from the state. The temps Friday will be around 48 to 50 for the high, which may also set a daily record. The weekend numbers will make some improvement after a cold Saturday morning in the mid-30s. Spring like weather will return early next week with 70s by Monday. It's worth noting that the EURO also brings another cold front into the area around Wednesday of next week, but not with the magnitude of cold air we'll see tomorrow.
Here's the bottom line: Windy and warm today with highs near 80 followed by storm chances tonight. Some could be severe, but the probability for severe storms will be very low. Thursday will feature showers, strong north winds, and record cold temps.
I would check the forecast several times over the next few days regarding the possibility for a winter mix or freezing temps.
The high in Tulsa yesterday was 84 at 4:10pm.
The normal daily average high is 76 and the low is 55.
Our daily records include a high of 91 from 2002 and a low of 32 from 1909.
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I'll be discussing this crazy forecast with Dan Potter and the KRMG Morning News this morning.
You'll also hear the regional and statewide forecasts on numerous Radio Oklahoma News Network affiliates across the state this morning through the early afternoon.
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