Not much has changed from the previous outlook issued yesterday afternoon. Our thinking for the last week has been that some sort of severe weather event will take place this upcoming week and that has come to fruition. There is still a lot of uncertainty involved with this event like timing and placement but those issues are slowly falling into place this Sunday afternoon. We are still 48 hours out from the event so things will still be fine-tuned between now and Tuesday morning. All modes of severe weather are possible with this event with large hail and damaging winds the primary threat. Tornadoes are a possibility Tuesday afternoon and evening ahead of the main line of thunderstorms. If we get additional backing of the winds front the southeast then that threat could increase, and is very possible it will, given the dynamics in place especially early in the evening Tuesday. This will start with the warm front moving north tonight that is ongoing at this time. Very small chance of severe thunderstorms confined to far southwest Arkansas for a hail threat. The main system will be approaching the state from the southwest lifting a warm front north tonight and Monday. There will be a break Monday night and Tuesday before the main round comes in. The cold front will be moving through Tuesday night and Wednesday with a line of thunderstorms along it. This line could slow down and move through Wednesday afternoon across the east increasing the severe threat. This looks like a multi-day event although severe weather will not be seen every day. Let’s break it down day by day for you below:
TONIGHT: (MARGINAL RISK) Currently showers and thunderstorms are increasing across the forecast area. This is in response to a warm front beginning to approach the state. This warm front will lift north tonight and Monday bringing showers and thunderstorms along it. There will be a lot of rain with the warm air advection keeping the severe threat lower. Three is a marginal risk for a very small part of southwest Arkansas for Miller and Lafayette counties for marginally severe hail or hail 1 inch in diameter. Right now, this is a very low threat. With the cold air aloft storms are producing hail but most of it is tiny like pea or marble size hail. These strongest storms, especially later tonight will have this capability. They will be loud to but no sever weather is expected other than a very low chance in the southwest. This will be a rainy night however with a lot of rain around the warm front.
MONDAY: (GENERAL THUNDERSTORM RISK) Monday warm air advection will be ongoing across the state during the morning hours. As the warm front lifts north showers and thunderstorms will become much more isolated and the afternoon will see mostly light rain or drizzle as we sit and wait on the main system. The entire state has a general thunderstorms risk and this means that no severe weather is expected to occur. You can get an isolated severe storm but that chance is low. There will be thunderstorms but nothing too bad. By the evening most activity should have exited the area with only isolated thunderstorms possible.
TUESDAY: (ENHANCED RISK) This is the key day to watch. A strong upper level low will be approaching form the southwest. Latest data has this low moving to the northeast through the southern plains and Ozarks of southern Missouri. Data also has a very strong jet streak in place, one that is typical of April not February coming across the state Tuesday afternoon and night. This will provide plenty of wind support for thunderstorm updrafts and movement at very fast speeds. Shear will also be present surrounding this system. Data has come back more aggressive today with the shear values. This is concerning because if they do verify then we could see a more apparent tornado risk especially if the winds back out of the southeast. There will be ample amount of moisture in place and instability levels look sufficient enough for all modes of severe weather. There are a few uncertain aspects around this event and that is timing, placement, and if storms can get going early enough. Data has shown little to no thermal inversion or “cap” in the atmosphere preventing storm development. IF this holds then we should see both discreet cells and a line later in the evening. If we get cells out ahead of the main line, then a tornado thereat will exist. The timing has been anywhere from early afternoon to late night for storm initiation. Using a blend of the data, storm inhiation looks to occur during the prime time of the afternoon across the west and gradually move east as the night wears on. IF storms fire in the afternoon hours, then there will be threat for at least isolated tornadoes. There will be plenty of shear present for development, the question will be timing. Another big aspect will be placement. Data has been consistent in bringing the low through the aforementioned track but as of late has shifted either slightly north or slightly south. Right now, I do feel the whole state will be under a threat for severe weather but the NW 2/3rds will see the greatest threat. Or a Texarkana to Jonesboro line points NW. There will be plenty of cold air aloft so hail will be a big threat with strong damaging winds the main threat, especially with the line Tuesday night along the cold front. How fast this system moves will determine when the storms begin. Timing looks to be midafternoon through the night. There is an ENHANCED RISK from DE QUEEN TO FAYETTEVILLE TO CORNING TO BLYTHEVILLE TO PINE BLUFF TO NASHVILLE with a SLIGHT RISK from TEXARKANA TO MEMPHIS. A MARGINAL RISK is out for Ashley and Chicot counites, mainly because your threat may exist more on Wednesday. The Enhanced risk is for damaging winds and large hail but this is also where the greatest chance for tornado development will be. The slight risk is more for winds but there will be a chance for hail here to. Tornado development will be lower here but it will still be possible as with any severe thunderstorm. Low threat for anything in the marginal risk.
WEDNESDAY: (SLIGHT RISK TO ENDHANCED RISK) This is the most uncertain day. Thunderstorms will be ongoing across the state. A faster moving system which is what tends to happen, then the threat lowers for the eastern half of the state. A slower moving system means a later threat Tuesday but the threat will extend well into Wednesday. There is a slight risk with an enhanced over the far east on Wednesday for damaging winds and large hail. By Wednesday most data has the low pulling off to the east with the cold front trailing lowering the chance of a tornado threat across Arkansas. There could be a window of opportunity if the system slows town for potential tornado development across the southeast but as of tonight, this threat looks lower. Timing is the biggest issue and placement for Wednesday and that is to be expected this far out. This day could also see all modes of severe weather as well. There is a slight risk potential from Texarkana to Little Rock to Jonesboro with enhanced risk potential from Crossett to Hamburg to De Witt to Helena points SE. North of that area the front will be past you ending any sever threat.
The biggest thing to remember regarding the latter part of this outlook is that this can and will change some as we are still 48 hours out of the main event. The track and speed of the low will ultimately determine what we see and when. This could very well turn into an overnight event and would not be surprised if it did. This could also be a greater risk than is currently listed also a lesser risk. That also depends on aforementioned variables as well as the cap and other factors could affect this entire outlook but this is a high confidence forecast regarding severe weather potential. This does NOT look like an outbreak at this time but there look to be at least several rounds of thunderstorms with the potential of severe weather becoming increasingly likely through the day and night on Tuesday. I have seen these setups go crazy and I have seen them turn into nothing. IF we see a lot of sunshine then we could get quite active, if we see a lot of clouds and rain then we could see a lower threat. Temperatures will play a big role to in the evolution of this event. Right now, forecast highs are expected to be near record levels. With strong warm air advection, I do not see any issue not reaching those levels even with the cloud cover. Below are the outlooks for severe weather tonight through Wednesday as well as the rainfall outlook. Remember this can change some as there is still plenty of room for error. This will be monitored as additional data comes in and can be analyzed. Stay tuned to future outlooks and updates regarding this potential severe weather event. Next outlook will be issued MONDAY NIGHT, the final outlook forecast for this event before all day coverage on Tuesday and possibly Wednesday.
~Senior Forecaster Derek