Good evening everyone, hope you’re having a great end to your weekend. Not much has changed regarding the system coming in overnight tonight and on Monday. Still expecting to see heavy rain and thunderstorms some of which could be strong.One thing that I am still questioning is the amount of severe weather we will see. Currently temps are much colder than expected. A warm front will lift north overnight and allow for a rapid return of Gulf moisture on strong southerly winds. There will also be a good amount of shear for storms but dew points will only be marginal. Another thing about it is that even with the warm up, temps will only manage the 60s under extensive cloud cover and heavy rain. Some places in the far southern part of the state could see 70 and this is where the largest threat for severe storms would be. The rain will limit atmospheric heating, one key ingredient needed for organized severe weather. Right now, the largest severe threat will be damaging straight line winds given the amount of wind shear in the atmosphere. Most areas will see winds at least 15 mph tomorrow outside of main storms. So wind will be present with this system. In the slight risk area, there will be more of a chance for damaging winds. The tornado threat is VERY LOW with this, but any storm that can get surface based will have a chance to rotate and increase the tornado threat across southeast Arkansas. Best chance for that to happen will be along the highway 82 corridor from Texarkana to Lake Village close to Louisiana. Even then the threat is still very low. Overall severe threat will be isolated at best but the potential is there in the slight risk area. Below is the Severe risk area as it sits today. Will have an updated map in the morning.
Flooding will be an isolated concern with this system given the amount of dry ground we have had recently. With the wind blowing tomorrow, leaves will clog up drainage systems so there will be a threat of flooding near poor drainage. Otherwise not expecting to see widespread flooding tomorrow. Most areas will see at least an inch of rain with some seeing up to 2. Along the Mississippi rain amounts may approach 3 inches. There will be isolated higher and lower amounts depending on where the heaviest bands set up. Right now that looks to be from Texarkana to Little Rock to Mt Home east. This will be more of a soaking rain vs a fast mover. Below are expected rainfall amounts as of today. This will be updated in the morning also
The timing of this system is as follows:
WEST 1/3 ARKANSAS: BEGIN AFTER MIDNIGHT AND END AROUND LATE AFTERNOON
CENTRAL 1/3 ARKANSAS: BEGIN AROUND 3 TO 5AM END EARLY EVENING
EASTERN 1/3 ARKANSAS: BEGIN AROUND OR JUST AFTER SUNRISE END LATE EVENING TO AROUND MIDNIGHT.
This is an estimated timing on this system and it could be delayed or sooner, depending the track and speed of the storm system. Once this moves through it will be a quiet week ahead with temps getting colder as we head into the weekend.
I will have an update in the morning with your forecast around 5 to update any changes made and I have a feeling some may be made.
Hello everyone, I know it has been a while since I wrote up anything involving weather on the site thanks to some rather benign weather this fall so far. This has been one of the drier falls on record. We had a cold front move through yesterday with the entire state receiving rain, some their first since August. Not a very normal fall to say the least. At least we have fall temps across the state finally. Most places seeing 50s across the region today vs the 80s we have seen. Tonight, the entire region will see the end of the growing season with temps in the 20s to near freezing for several hours. In our Winter outlook posted above, we said the first freeze would be between November 5th-15th. Only missed it by 4 days. Freeze warning in effect for this reason. Most will lean to think that due to the warm fall, we won’t have much of a winter. Well my friends, those folks may be in for a very rude awakening. I have been dissecting data for several days now and the patterns falling into place and I like what I see. Let’s look.
First off let’s look at one thing we look at for winter temps and weather during a La Nina season. With cooler temps over the equatorial Pacific, we lose that player in our field being so far south. The cooler it is the less cold air makes it without some help. Fortunately, La Nina is weak this year which tends to favor more cold air intrusions east of the Rockies and especially into Arkansas. The Arctic is very warm this year. That means that the Polar Vortex, which the term given to the main supplier of cold air up north, is weaker. The colder the Arctic the stronger the vortex. Why does this matter? Well to get cold air, especially snowfall producing air to intrude this far south, we need a weaker vortex to break off from the main one and ride the polar jet to plunge our temps down. Looking at this upcoming winter and comparing it to similar ones, like 2000 and 1983, the weaker vortex and warmer Arctic could counteract La Nina and keep temps below normal and provide long stretches of colder air. Another player we look for is the Arctic Oscillation. This index doesn’t normally have a say in what weather we get, but is great tool for figuring out what the data is seeing. A Positive AO means a lot of warmer weather. A Negative AO means colder weather is likely. For most of the fall, we have been in a Positive AO sometimes very positive. This has led to record warmth across most of the U.S. and kept the cold bottled up in Siberia. As we head into December, this looks to be changing. The AO has already taken a dive and all major data shows a continuing negative AO heading into December through mid-month the furthest we can view now. Given it is still November, we will have some temperature swings, but anything major looks to be winding down. IF this stays negative as we head through December, this is a good sign that colder air will be moving south. If we get a storm system in place with colder air, well everyone remembers Christmas 2012, then anything is possible.
Another reason why the teleconnections are so important, is seeing where guidance is taking temps in the next 16 days. This is very close to what the AO is doing above. As you can see 1st in the day 1-5 we are below average like today. This is the beginning of the change. We have had 2 cold air intrusions in the last 14 days. We had NONE before that. Yes, they are short lived, but each one takes us lower than the previous. This looks to be more common in the next few weeks as each front either keeps us average or drops us below but the importance is it keeps us from rising too much. The next set in the day 6-11-time frame you can see a slight warm up. This is in response to a cold front moving across the country after Thanksgiving. This front must be watched for severe weather but too far out to be determined and will be discussed later. Even with the “warm up” temps still stay close to seasonal averages. This is important because one the rainfall, 2 it’s a sign of a more active pattern starting and 3 the consistent waves of colder air. The best way for us to get Arctic air unmodified this far south is a thick snowpack to the north in the plains. As temp’s tumble heading into December, snowfall looks to pick up from each storm system. This will help determine if we can start seeing highs in the 30s and 40s again sooner than last year. This is really starting to remind me of December 2013 when it was warm 3 days before my wedding then we had ice and snow from December 5th through the 15th and it was still on the ground December 23rd. Not saying that will happen this year but climatological data seems to be heading that way. Beyond this timeframe is the most important to me, the 11-16-day outlook. This tells me that the cold is starting to break away from the arctic. You see the blocking up in Alaska, this is a BIG player to get cold air here. You also see the warm ridging over Canada and the cold air over most the country, this is what we call the Greenland block, where the colder air is shoved south. 2 separate models show the same story one just colder than the other. That being said, our first taste of winter temps may not be that far away. If we get snowfall up north, then our temps COULD be colder than even this forecaster thinks. Time will tell on this. This data below shows the departure from average. This would mean we could see temps 1 to 5 degrees below average over a 5-day span some of which could be colder than others. I do think this is the beginning of a long-term change, and the strength of the front after Thanksgiving will go a long way into determining how strong of a cold shot we get. Will there be warm days, yes because we live in the south, but I feel the colder days are about to outnumber the warmer ones shortly.
One last thing I want to show everyone is the monthly snowfall ensemble. TAKE THIS WITH A GRAIN OF SALT. This is what caught my eye lining up with the other teleconnections. This is the CFSv2 ensemble snowfall forecast for DECEMBER for the United States. There are 4 different runs of it all pictured here. ALL 4 blanket the US and Arkansas in snow through New Year’s Day. This is forecast snowfall amounts by New Year’s Day. Reason why I say take this with a grain of salt is simply because nothing can know the amounts of anything a month out. However, I have seen this model verify before (2013, 2012,2011,2008) IF this were to verify we could see our 2nd White Christmas in 4 years. I have my doubts on this, but given the other teleconnections, this is also has a good likelihood to verify. Most ensembles give Arkansas our yearly snowfall in one month. This does not factor in any ice events or sleet events. Warm Air aloft with cold air at the surface is a killer to us when it comes to snow. We have seen this happen many times here in the natural state where 6 inches of snow was forecast and freezing rain was the result. With that being said, looking at all the teleconnections at play, the 2 on the right have a greater chance at verifying. I don’t think we will see a lot of snow, but a few winter weather events are looking more possible as we head into December, especially towards Christmas. With all ensemble agreeing which is rare, I do believe someone gets snow in December, possibly more than one event. December is generally the month the sub-tropical jet gets ramped up and also when the polar jet likes to dive south. IF these two meet with a storm system in place, then we could see a good winter storm. Our tracks need to be along or south of I-20 for decent winter storms across the state so storm track over the next few weeks will need to be watched closely. Like I said take this with a grain of salt but also in the back of your mind as you are planning those parties and get together. Any snow or ice event will be covered in detail by your AWW team up to a week to 10 days out so you have plenty of notice.
With everything above showing colder, there is always a curve ball in the weather, one that no one sees coming even us. We pride ourselves in the accuracy of our winter weather forecasts because we wait until we see exact tracks, temperatures, and precip values in the atmosphere before ever giving you an amount of snow, sleet, or ice. We have hit our forecasts last 2 years with 90% accuracy. You can never get them all right but we think we do good. That being said, there is good indications that we are leaving summer in the dust. We won’t have much of fall, but could have an extended winter or an early start to it. Warm days will be there but few and far between and cold nights will be the norm. I do feel we will have a December to Remember with several winter events over the course of the month and first week of January. We are still in a weak La Nina so that could be our curve ball and provide enough Pacific air aloft to give us more of a sleet and freezing rain show vs snow, but all aspects are in play. We need rain more than anything and that looks to pick up as well as we get the storm train rolling. The afternoon runs of the European models are coming in and continue to support my thinking and could be sooner than I think for some of you but will wait on that. So, get ready Arkansas because a wild ride is about to take shape as we head into what I feel will be a December to Remember.
~Senior Forecaster Derek