We just had the wettest April on record and the month of May was also wetter than normal, so why has it dried out so quickly some may be asking. Notice the following map courtesy of the OK Mesonet, which shows the number of days since each location had received as much as ¼ inch of rain. Those numbers do not include today as the day is not yet over, but obviously you could add one more day to each of the totals. The point is that is has been more than 3 weeks for some of us since we last had as much as ¼” of rain.
Now, combine the lack of recent rains with the fact that this recent warm spell together with strong southerly winds has resulted in high evaporation rates. For example, the calculated evaporation rate for the calendar day yesterday was as high as 0.427” at Ft Gibson Lake and some of the lakes in W OK exceeded ½”. These warmer than normal temperatures, the mostly sunny skies, and gusty winds all contribute to those high evaporation rates and that is going to be an issue for several more days at least.
Speaking of warmer than normal temperatures, notice the max/min temperature map for today and keep in mind that the normal values for Tulsa at this time of year is 87/67. So far, today’s numbers have been 92/73.
However, that is only part of the story as the dew point has been holding in the upper 60s to lower 70s throughout the day and that has created a more uncomfortable level of heat and humidity. The heat index in Tulsa has topped out in the upper 90s today as has been the case for many other locations.
Those high dew points together with southerly winds continuing at 10-15 overnight will keep temperatures from cooling much and Tuesday morning will again start off in the low-mid 70s. We will also have considerable low level cloud cover by morning, but no mention of rain. Those morning clouds will then be burning off as the day wears on, much like we experienced today, and that will allow afternoon temperatures to reach the upper 80s to lower 90s once again. Also, heat index values will be in the upper 90s to near 100 along with gusty southerly winds so Tuesday looks to be very similar to what we experienced today.
Wednesday will be similar in many ways as well but there will be at least a chance of a few showers/storms that night and into the day Thursday. In fact, the pattern aloft will be somewhat more supportive of at least a chance of scattered showers/storms starting Wednesday night and continuing off and on into the coming weekend. That does not, by any means, suggest a complete rain out as the chances of any one location receiving measurable rainfall through the period is still rather low as you can see on our forecast page. Notice also that the 7 day QPF is not showing a particularly wet signal either. A few locations will likely receive more than this would suggest, but the heavier showers/storms still look to be very widely scattered so many will miss out altogether or only have very light amounts.
As is often the case, the longer-range guidance is diverging by early next week with some of the data suggesting a weak front may arrive and if so would cool us off at least somewhat. Other data runs are not overly optimistic the boundary will make it this far south and therefore is holding off on much in the way of additional rainfall or any cooling by then.
As we extend into the 8-14 day time frame, the outlook suggests near to above normal temperatures along with a near normal pattern for scattered showers/storms. By then, our normal daytime highs are near 90.
So, stay tuned for updates.