SHOWERS ON SOME SHAMROCKS...
Fantastic spring weather prevailed around the Midwest Wednesday with highs reaching 70 along and south of I-80. Mostly sunny skies and a gentle breeze added to the overall perfection of the day. Now it's St Patrick's day and while Irish eyes are smiling, our run of weather luck is quickly running out. By the end of the day, showers may fall on our leprechauns and shamrocks near and north of I-80. Keep your lucky charms and umbrellas handy up that way. The south remains nice and mild. Everybody gets a chance to use the umbrella Thursday night through Friday night as a slow moving storm brings rain, colder temps., and perhaps snow to some in the west.
MUCH NEEDED RAIN...
The change in our weather is tied to an upper air low which briefly closes off at 500mb as it emerges from the Texas Panhandle. The sub-tropical jet generates a nice flow of moisture and a lengthy period of warm air advection. Here's the 500mb jet structure Friday morning as the system enters Missouri.
You can watch the evolution of the surface features and precipitation pattern in this animation of the EURO Thursday morning through Saturday afternoon.
That's a pretty good sized rain shield. With much of my area in abnormally dry to moderate drought conditions and the growing season fast approaching, the rain is needed.
As far as precipitation totals are concerned, models continue to crank out 1/2 to 1 inch amounts on all of my area. However, there is some variability where the heaviest rains occur which you can see in the rainfall forecasts below.
The EURO
The GFS
The 3k NAM
The 12k NAM
The GEM
Another aspect of the storm which is going to be challenging is the threat of wet snow in the northwest third of my area. If snow develops, it's most likely to occur later Friday or more likely Friday night, as temperatures cool after sunset. If I had to make a guess right now, I would say any snow would be just out of my area northwest of Cedar Rapids and Dubuque. Even if snow occurs in the far northwest, with recent warmth it's unsure how much of it would stick to roads. It may very well be that any light accumulations would be on grassy and elevated surfaces. We will have to watch this closely as we obtain more data and get closer to the event. Right now I just don't see much in the way of snow in my area. Here's what models are currently showing for snow totals. Note there is a wide range of solutions and confidence remains very low any one being correct. Also keep in mind that what you are looking at is just raw model output and not official forecasts. This is the data we look at to ascertain trends that eventually lead to forecasts.
The GFS (the snowiest and most ominous out west)
The NAM, close to the GFS