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THROW IT OUT WITH THE BATH WATER...

The weekend is upon on us and for those of you making Mother's Day plans, It looks as if this year will be a far cry from last Sunday when highs were in the mid to upper 80s. Readings will be 25-30 degrees cooler and at least in the south, the day could begin with rain. Throw it out with the bath water!


Having said that, there are some significant model differences that will determine just how poor Sunday turns out. I will address that in bit. First and foremost, Friday looks to be a pleasant day with mostly sunny skies and a worthy appearance. Temperatures will again be on the cool side, aided by a fresh NW wind that could gust up to 25 mph. Most highs should end up close to 60.


Friday night we'll need to keep an eye out for frost potential, especially in the NE half. As winds diminish and skies remain clear, the dry air will rapidly cool after sunset. Most areas have a good chance of reaching the mid 30s with a few of the colder low lying locations in the NE close to 32. It's getting pretty late for readings like that!

That leads us into Saturday and the weekend storm. The first impacts will be clouds which will be on the increase by afternoon. Precipitation is not expected to enter the picture until Saturday evening. There should be enough morning sunshine to allow highs to reach the upper 50s and low 60s, a solid 10 degrees below normal.


Now to the particulars of the storm which really focuses on the track and amount of rain that it eventually produces. The EURO, and for that matter the Canadian GEM are furthest south. Their track is no doubt dictated by the influence of dry northeasterly winds circulating around the storm center. You can see how available water vapor rapidly decreases north of I-80 on the EURO Sunday morning.

This animation (noon Saturday to daybreak Monday) shows the rain getting snipped off by the dry air in my northern counties. There's still some showers but amounts are minimal as the system if forced east southeast.

Getting to the point, the EURO has the bulk of the heavier rain remaining south of I-80, with the 1 inch+ totals closer to HWY 34 and south.

The GFS is decidedly further north. Here's its track and precipitation animation.

The GFS has 1 inch+ amounts all the way to HWY 20. In Clinton, Iowa the GFS has 2.45" while the EURO paints just .08". That's a huge difference all tied to the track.

Here's another fun little discrepancy, it's snowfall! The thermal profiles on the 12K NAM and GFS are cold enough for a period of snow late Saturday night or Sunday morning. They show this for totals. Very unlikely in my current opinion.


The 12K NAM

The GFS

As I stated a couple days ago, I think the GFS has some sort of feedback problem and is too far into the dry air with its precipitation shield. If it verifies it will be a big coup for the model and I will be impressed. Perhaps a compromise of some sort will be the ultimate solution. All I can say is dry air is a tough nut to crack and it will be a force in how far north the storm gets and will certainly create a sharp northern cut-off to the rain. I am leaning more towards what the EURO is selling. I'm also against the idea of any snow but a couple weeks earlier and it could have been a different story.


Last thing I will mention is temperatures Mother's Day. Any area that stays in clouds and precipitation the balance of Sunday is going to struggle to get much above 50. However, if the EURO rules we should see clearing move from north to south during the day and even a sniff of sunshine May 10th will get you close to 60. It sure looks like the further south you go, the worse the day will be. I'm expect things will be a little clearer in my next post. Until then, Roll weather...TS

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