Tuesday, February 20, 2018

If it quacks like a duck... (heavy rain expected)

Seems spring has sprung the past couple of days as we've reach temperatures in the mid to upper 70s both Monday and Tuesday. Monday's high tied a record set just last year at 77°. Today's record of 80° (also set last year) may be safe, but not my much. [Side note: the 80° reading last year on this date was the first time we had reached 80° in February in 32 years. We almost did it again today!]

A cold front approaches

The warm, moist air that brings 70s to the region will be the same water-loaded air that is responsible for periods of heavy rain in the coming 4-5 days. It all starts with a cold front that is literally separating winter from spring in the U.S. While the western U.S. shivers, the eastern U.S. is setting dozens of warm weather records. Near the boundary, rain, thunderstorms, and ice are falling as the front slides slowly southeast. (OKC dropped from 68° to 32° and freezing precipitation in just 3 hours!)

Early afternoon temperatures across the CONUS show clearly where the cold front is located. (WxBell)

Wet Wednesday

By Wednesday early morning, that front will move through the metro and the wet pattern commences. Tomorrow will be very similar to last Friday when a high temperature in the mid 60s occurred around morning rush hour and the mercury fell from there in rainfall. We will see temperatures above 60° around dawn, then fall through the 50s into the upper 40s by Wednesday evening with rainfall much of the day.

Though severe weather will not occur, we will likely hear some thunder around the time the front passes early in the day. The heaviest rain will likely occur Wednesday night as the "river of atmospheric moisture" above us is tapped by a passing upper level disturbance, effectively opening the spigot just a little bit further. Rainfall totals through Thursday morning will likely be in the 2-3" range or so for the metro.

NOAA's Weather Prediction Center forecasts approximately 2.5" of rain by Thursday morning. (WPC/WxBell)

A Moderate Risk (category 3 of 4) of excessive rainfall - enough to cause flooding - is forecast with our first round of precipitation Wednesday in to Wednesday night. Flash Flood Warnings are very possible as the event unfolds. (NOAA/WPC)

Thursday-Friday - a small reprieve?

Continued scattered showers are expected Thursday and Thursday night as the front lingers just to our south before pulling back to the north overnight as a warm front. Models have some disagreement on the rain chances Friday, with one camp showing rainfall remaining mainly to our northwest, while the European model is a little more aggressive with scattered storms on Friday. We'll call it TBD and tell you to be prepared for scattered precipitation! Temperatures will still warm up nicely into the lower 70s.

Saturday-Saturday Night - Wet Again

By Saturday and Saturday night though, we'll be moving into round 2 of heavy precipitation. As low pressure moves by to our north and that warm, moist airmass has re-established itself over the Mid-South, showers and thunderstorms will break out. A few storms have the capability of becoming strong with some hail or strong wind gusts possible, mainly during the afternoon and evening hours. With heavy rain also expected though, it's possible that the air may not be unstable enough to generate severe storms. Stay tuned.

The severe weather outlook for Saturday is equivalent to a "Slight Risk" of severe storms, or category 2 of 5 risk. This could change as we draw closer in time though. Follow MWN for the latest. (SPC)
Either way, the Mid-South could easily pick up another couple of inches of rain before it moves out with a frontal passage late Saturday night, yielding a 5-day total of 3-6", or an amount only a duck could be happy about...

Flood Watches are in effect for the entire area (including Memphis and Shelby County) through early Sunday morning . If you live in, or travel through, areas subject to flooding during heavy rain events, that will likely have again this week. As as reminder: "turn around, don't drown." The only way to ensure your safety is to stay out of the water.

Sunday brings a return of dry weather that should last through early next week. Hopefully, some good drying will take place with mild conditions. By then, the all-time February rainfall record (11.14") could be broken however.

River flooding

We'll also be watching the river levels in the area. With the expansive reach and overall amount of water that will fall over the coming week, rivers will be high and could also flood some areas. The spring flood season is starting, including watching the Mississippi River rise as we head into early March. It will also likely eclipse the low end of flood stage and could have ramifications for low-lying areas, including along its tributaries (the Wolf, Loosahatchie, and Nonconnah rivers).

Stay with MWN for the latest on the heavy rain threat(s) via our social media feeds and mobile app with the human-powered MWN Forecast (links below). We'll keep you updated throughout!

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!
MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

No comments: