Thursday, April 16, 2015

Rain chances increase again as we head into the weekend

A nice day overall today as weak high pressure built in behind scattered thunderstorms last evening! Highs have reached 80 at most locations with a partly cloudy to mostly sunny sky. However, the large upper level system that we talked about early this week that would keep things unsettled this week still lingers to our west, meaning wet weather is not over just yet!

The main upper level system is still well to our west, which means we'll deal with an unsettled pattern until it moves past us. It is forecast to be "absorbed" into the main upper level flow by this weekend. Graphic courtesy WxBell.


We'll likely see some more foggy areas in the morning, or at least low clouds, as moist ground and light south wind combine with cooling temperatures to push humidity levels above 90% and promote low clouds and fog. Another impulse from this big storm system will move through the area tomorrow as well, bringing a chance of showers and thunderstorms, mainly during the afternoon hours, though some model data is hinting at a bit of development early tomorrow morning as well.

The GFS model indicates scattered precipitation, likely a few t'storms, will be around tomorrow afternoon. Shown above is possible precipitation totals between 1-7pm Friday. Graphic courtesy WxBell.


The best chance of rain arrives Saturday however with heavy rain possible from late Saturday afternoon through Saturday evening. With high moisture content in the atmosphere and a potent weather-maker moving through, widespread rainfall totals of 1-2" look likely and some areas might see higher amounts. With recent rain and saturated ground, much of the water from this system could run off, resulting in full streams and creeks, high tributary levels (rivers that flow into the Mississippi), and possibly flash flooding. If you have outdoor plans Saturday, the sooner the better! Models still disagree on when the rain arrives, but the later it gets, the higher the chances.

NWS precipitation analysis for the past 7 days, showing total rainfall amounts. A swath of widespread 2-3" totals is easy to pick out across the Mid-South into the Ohio Valley. Additional rainfall will likely result in runoff. Graphic courtesy WxBell.
Forecast rainfall amounts from the NWS through Sunday morning. Widespread 1-2" amounts will be common.


Once that system moves out Saturday night, the main low pressure center responsible for the unsettled pattern will eject out of the Plains and move by to our north on Sunday. It will drag a cold front through the region that has the potential to bring some strong storms on Sunday afternoon and evening. The Storm Prediction Center is watching our the region roughly from Memphis north and west into AR and MO for this possibility. They currently give us a 15% chance of seeing severe weather within 25 miles. This roughly equates to a Slight Risk of severe weather (category 2 of 5), though that term is only used out to 3 days (Sunday is day 4).

The Storm Prediction Center outlines a 15% risk area for Sunday that includes the metro. This is roughly equivalent to a Slight Risk zone.

Looking ahead...

Finally, by early next week we'll dry out a bit on Monday and Tuesday with long-range models indicating a cooler pattern in store as we head towards the end of April.

NOAA's 6-10 Day outlook valid April 22-26 indicates a higher chance of below normal temps than above normal temps.

Erik Proseus
MWN Meteorologist

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