Cool mornings will linger until Wed.

We finally got down into the 50s on the Northshore. Slidell’s airport, a cold spot, hit 51 while my warm citrus grove bottomed out at 58. Louis Armstrong airport on the Southshore hit 62. On the Northshore…Expect 50s to near 60 to persist through Thursday, but with highs about 87. Then return flow will quickly bring back the humidity with the next front bringing in showers for the weekend.

Forecasts become uncertain beginning on Sunday as I’ll explain in the long-range ramblings section.

The Foreca graphic does well until the uncertainty arts on Sunday. Highs should increase a few degrees peaking at about 87 Tuesday - Thursday. The same can be said with the lows which should increase a few degrees each night. It won’t start to feel humid until the winds swing around to the SE during the day on Thursday. Note that the high temps. won’t increase any, but the lows will pop up to 70 by the weekend. Southshore lows mid 60s through Wednesday, then upper 60s on Thursday and low 70s for the weekend.

The graphic shows a chance of a shower on Friday, which the NWS tends to discount and I agree. However, Saturday does a feature a 20-30% chance of some scattered light showers. Then, the graphic pours on the showers and storms for Sunday and Monday - but I’ll discuss that in the long-range section.

One thing that the graphic does not show which could be problem on Friday or Saturday: early AM fog. Return flow of moist air from the Gulf coming over cooler land can cause this if the winds are light and there’s little cloud cover. Fall fog, though usually not as thick as the type we see in late winter, tends to be thickest in inland valley areas or near farm ponds rather than Lake Ponchartrain or the Mississippi Sound. Fog forecasting is tricky - so I’ll take another look at this later in the week.

The challenge for Sunday and early next week lies in the timing and location of the system. Most models are like the German ICON whose forecast for next Sunday afternoon is shown below. The showers and storms move through Saturday night and Sunday morning ending quickly with most of the upper level energy further north, say Tennessee. Sunday afternoon would clear quickly with next Monday morning’s lows near 60 and low 50s for that Tuesday.

On the other hand, the European (ECMWF) model favors a slower solution with a system moving just north of us across MIssissippi. And, this map is for next Monday morning, not Sunday to give you an idea of how much slower the ECMWF is. This would give us several rounds of showers and storms from mid-day Sunday into Monday morning and heavier rainfall. It could also give us the threat for severe weather late Sunday into Monday morning and keep the temperatures warmer than the ICON for early next week.

Why the difference? It’s not so much the difference in modeling as it is the way models are capturing pockets of energy in the jet streams over the Pacific. A lack of upper air winds can often play havoc here, especially if the energy is well away from aircraft routes. As that energy approaches Alaska, Canada, and the West Coast in a few days, observations will capture it and models will converge on a consensus. Again, I’ll look at it on Tuesday.

Ended for the season - will resume next April.