NEAR TERM: (TUE-WED)
Active pattern continues to start the period. Isolated showers and storms around the state will dissipate after sunset tonight. However, this will not be the end of the active pattern. To the west, a cold front and upper level system will move through the region late tonight and Tuesday with showers and thunderstorms redeveloping after midnight across the southern half of the state pushing eastward with time as the front sinks southward through the day on Tuesday.
Tuesday, I have included a low end chance of a shower or storm for areas north of 40 to account for any left over boundaries but the brunt of the rainfall will be along and south of 40. Rain chances will diminish from north to south during the day on Tuesday as the front continues to sink southward with time. The front will shift to near the Louisiana border on Wednesday with a stray shower possible along it on Wednesday while high pressure moves in behind the front to keep the rest of us sunny and dry on Wednesday.
Severe threat is very low, but it is June so isolated severe weather can not be ruled out. This round of storms does hold a flood potential though given already saturated soils in southern Arkansas where 4-8 inches of rain fell on Sunday night and early Monday. This will be the main threat with this round along with easily uprooting trees due to saturated soils. This hazard will be watched closely overnight.
Another thing to note will be the temp/humidity change during the period. The front will bring a brief reprieve from the humidity overnight Tuesday and on Wednesday with low in the 50s and 60s and highs in the 80s. Tuesday will be one of those odd days where the south could be cooler than the north with clouds and rainfall versus sunshine. Forecast reflects this as well.
Period b begins with high pressure over the region shifting eastward rather swiftly. To the south, a layer of Saharan dust in the upper levels will be approaching the Gulf Coast. We will get to that in a bit. A low pressure will be located in the central Plains as well.
As the high shifts east and the low deepens, this will bring a rather fast return to humid conditions as southerly and southwesterly flow returns in earnest. Warm air advection will return giving us a few more clouds than on Wednesday. I have added a small rain chance to Thursday to account for any WAA showers that do pop up but most of us will be humid and dry.
By the weekend, upper flow will be amplifying as a trough digs southward. This will enhance southwesterly flow with ample amounts of moisture seen. Guidance is keen on bringing shortwaves through the mean flow aloft through the weekend and into the end of June and first of July. I have gone with low end rain chances to account for this but I am not fully sold on rainfall during the period and here is why.
A layer of Saharan Dust (common for June) will be moving through the upper atmosphere. This brings really great sunrises and sunsets and very hazy skies. It usually does not mix down to the surface but on occasion can. Current forecasts do make this a more upper scale dust event in our part of the country. What this means is that this could inhibit storm development creating widespread stable air across the region. We will have plenty of lift and humidity for storms but given this area of sinking air, it will act as a cap to prevent widespread coverage. For this reason, I have kept chances on the low end side and could end up being pulled by later shifts as we get an exact idea on how the dust layer will affect the area. Regardless it will be a summer time pattern with hot/humid days and warm/muggy nights.
Heat index values will be creeping up as well towards the end of the period to near 100 with the increase in humidity. Fortunately, the rainfall as of late will keep air temps in check for now. Some guidance is dry and toasty for the 4th of July weekend, but we will wait and see on that.
~Chief Forecaster Derek