Sunday Weather Discussion: The Week Ahead 4/15/18

Good morning to the Foothills Weather Nation. We hope you've been keeping close with us in the last couple of days to best prepare yourself today. Our team put out a new round of high impact weather graphics discussing the what, when, where, and how much at around 11 pm last night and we will be putting out another round of information before the day is done. While paying close attention to today as a particularly weather action Sunday, I'm going to give a quick discussion about what to expect for the week ahead. I'll do my best to keep it quick!

Short term forecast (Sunday-Tuesday)

Today an intense cold front associated with a well developed trough will be crossing into the area. This set up has been seen for there abouts of a week or so, but has really solidified in forecast within the last 48 hours. Here is the most recent graphic from the Storm Prediction Center: 

 Apr 15, 2018 0600 UTC Day 1 Convective Outlook

Apr 15, 2018 0600 UTC Day 1 Convective Outlook

As you can see our area seems to be right in the bulls-eye on this one. So what do these labels mean? Did you know that it means different things depending how many days out we are looking? Here's what Enhanced means for a Day 1 Convective Outlook: 

 http://www.spc.noaa.gov/misc/SPC_5-tier_Convective_Outlook_Info_files/image002.png

http://www.spc.noaa.gov/misc/SPC_5-tier_Convective_Outlook_Info_files/image002.png

So you see it's broken up into three categories: tornado, wind, and hail. With our region being in the enhanced and some of us in the higher country in slight you can see we have about a 5-15% chance of a tornado today, which is significant for this area. Wind- especially straight line winds which can be just as damaging as a tornado and hail are not out of the question of concern as well today in this frontal passage. Winds will be a bit blustery today with mostly southerly winds today of 12-15 mph and gusts of around 25 mph. This will likely be higher in higher elevations as many of you could already guess, and this could all become more severe depending on the specific cells that will pass through today. Expect somewhere between an inch or two inches of rain with a bit of local variation and a daily high in the low 70's. This deserves more information, but I will leave it for the Sunday specific discussions and get on with the rest of the forecast.

Monday our trough axis will be moving offshore and we will be in the dry pocket of a building ridge. Between Monday and Tuesday we will be locked into a bit of cooler temperatures with Monday's high in the upper 50's and Tuesday's high in the upper 60's. Nightly lows will be in the upper 30's and upper 40's respectively. Plenty of sunshine in this time, attempting to dry us out. Here's a synoptic look at our 850 mb temperature map for Tuesday:

GFSUS_850_temp_057.png

As you can see we are pretty locked in on this colder region still on Tuesday, but come Tuesday night into Wednesday we will have a harder pivot into the warmer temperatures as our ridge propagates eastward, shifting it's warm axis closer and closer.

Mid Term (Tuesday night into Thursday night)

Here we will see much warmer temperatures and still an abundance of sunshine thanks to a lack of precipitable water. Thanks to this lack of water we can see dry adiabatic heating and cooling which is weather folk lingo for the fact that the air can heat up and cool down a lot faster and therefore a lot more. Think how the Sahara can be 100 degrees in the day and 40 degrees at night. That's very dry, so that's not quite the extremity we will see. For Wednesday and Thursday we will see daily highs in the low 80's and mid 70's respectively, nightly lows upper 40's/low 50's for both days. Here's another 850 mb temperature map for Thursday

GFSUS_850_temp_096.png

Now if you were to do a side by side comparison of the map I showed you for Tuesday and the map I show you now of Thursday you might see that there are similar features in that we are in the presence of a trough with a massive one exiting on Tuesday and a moderate one entering on Thursday. So do we need to be on guard?

Long range (Friday-Sunday)

No, we don't need to worry about our weekend trough and cold frontal passage in the same way. This one will be less developed, has more reasonable gradients of temperature and jet maximums, and lastly it seems to more or less clip us from the north on the last few GFS model runs. Here's the last 850 mb map- I promise.

GFSUS_850_temp_153.png

Here's the map for Saturday. As you might be able to infer we start to feel our cold frontal passage by this time which seems to be a pretty small scale event all in all. Daily highs for the weekend will drop down into the upper 60's for the day and mid 40's for the nights. Saturday night into Sunday is where we currently have our sights set for a precipitation event. Here's a precipitable water map 

GFSMA_prec_pwat_186.png

You can see that nose of moisture jutting up into NC oh so conveniently during the end of our weekend. Try not to fret- this seems to be a quick ordeal so Saturday will have building cloud coverage with maybe some rain overnight into Sunday and Sunday should show us some of those famous April showers. 

But for a second if I may to go back and discuss Saturday's 850 mb temperature map once more looking at something else. There is yet another trough building in the Plains with full intentions of marching east as today's trough will do, and next weekend's trough will do. Can you see the longer scale pattern forming here? This is near textbook for spring time synoptic setups. As we encroach into summer territory our warm and cold gradient will diminish making these specific events less frequent. 

I believe that's plenty enough of information. So much for keeping it short. Thank you very much for reading.

-Sinead Lockhart