The two maps on the right illustrate why our summer rainfall is so important with respect to the impact it can have on temperatures. The top map shows the soil moisture at 2" under sod and you can clearly see how much wetter some areas are than others, particularly just NE of Tulsa where the recent rains dropped up to 2" or more. Then, there is LeFlore county which has missed out on the recent rainfall and clearly shows up as quite dry. The second map then shows the maximum temperatures so far today and notice that LeFlore County was in the mid-upper 90s whereas the wetter locations were in the mid-upper 80s.
That is what we refer to as a rain footprint. The evapotranspiration from the recent rainfall has a cooling effect which can be quite noticeable. The rain footprint will also be a factor in our daytime highs as we go through the weekend and into next week, but since there is no additional rainfall in the forecast, then things will be quickly drying out and that effect will have less and less of an impact each day.
The NE winds today have also helped keep us dry and relatively mild, but that will be changing over the weekend. Light winds tonight along with fair skies and low dew points will allow temperatures to drop into the 60s to near 70 to start the day Saturday. Southerly winds will be increasing to 10-20 mph during the day Saturday and a more SW wind is expected on Sunday. Mid-upper 90s are expected for Saturday and upper 90s to lower 100s for Sunday. Anytime we get a westerly wind component during the warm season, that results in warmer temperatures. The wild card this time is the effect of the rain footprint and the impact it will have on temperatures. For now, it looks like the rain footprint will hold those areas in the 90s with triple digits elsewhere.
With ridging aloft building over the state and remaining dominant for much of the coming week, that also means there is little or no mention of rain anytime soon which also means things will be drying out rather quickly. So, the heat will be building for much of the week with the possible exception of Tuesday when a backdoor front will briefly shift our winds to a more E direction. Southerly winds will quickly return for the latter part of the week though.
Another wild card to consider is the potential for a strong tropical system to form in the Gulf of Mexico. Depending on where it eventually goes, it may have an impact on our weather for late next week. Too early to make a call on that just yet.
So, in the meantime, prepare for the hottest weather so far this season not only for the weekend but during the coming week as well.