A quick look at the map on the right shows how widespread and oppressive the heat has been so far today across the state. This is from the good folks at the OK Mesonet and shows the lows this morning and the highs as of late this Sunday afternoon. Not a pretty picture.
Although the daytime temperatures is what most folks will focus on, the morning lows are also significant and in fact have been record setting in at least a few instances. These extremely warm nights just do not provide much relief from the extreme daytime heat and creates additional stress on cooling systems not to mention the human body.
Monday is still shaping up to be the hottest day so far and in fact we will likely start off by setting another record warm morning low. However, it probably will not make it into the record books officially as a front will be arriving by late in the afternoon and we should be cooler than that before the midnight hour arrives. Ahead of this front, our winds will be veering to a more SW direction which together with abundant sunshine and the extremely warm start should result in triple digit heat for most of us by late afternoon. Heat index values will be in the dangerous 105 range and thus the heat warning that is in effect.
Each successive computer model run has brought this frontal boundary in a little quicker than the previous runs so we may not exceed the record 102 for Monday afternoon, but it will be close. Current projections bring the boundary to near the I-44 corridor by late afternoon and on across much of the area by early Tuesday morning. It will stall out south of I-40 and become diffuse or dissipate by Tue night or Wed morning. The more NE to E wind component behind the front and the mostly cloudy skies for much of the day Tuesday will provide at least a brief break in the excessive heat.
This boundary will also provide our best chance of showers/storms with about a 30% chance for Monday night through the day Tuesday. Some showers/storms may linger into the early morning hours of Wed and those storms that do develop will have the potential to become severe and drop some locally heavy rainfall. Ordinarily, a front moving through along with the high dew point temperatures at this time of year would produce a much more widespread convective event. But, a layer of very warm, dry air aloft will provide a formidable capping inversion which will be difficult to overcome. Thus, the marginal rainfall chances.
After that, the ridging aloft becomes more dominant and our surface winds return to a more southerly direction. That means the heat and humidity will build back in for the latter part of the week and the coming weekend. Current projections suggest a weaker pressure gradient by then which means southerly winds will not be as strong and gusty as they have been lately. This is a good news/bad news situation. The lighter winds should allow for somewhat better cooling overnight, but the lighter winds also mean not much of a cooling breeze during the day. In other words, the heat and humidity may be even more stifling by then and our chances of a cooling shower or storm will be in the slim to none category.
So, stay cool, stay tuned, and check back for updates.