Pattern shift: warmer but wetter weather on tap

Yesterday (January 6), the Memphis metro saw it's first 50-degree day since Christmas Eve!  Typically 52 degrees wouldn't feel that warm, but in the context of 30s and 40s the past week and a half, it was rather pleasant!  While today's weather is much like yesterday, more "spring-like" weather is expected for the rest of the week.  And with springtime temps typically comes spring storms - this week will be no exception.

The culprit for this week's wet weather will be an upper level low pressure system that will move out of Baja California across northern Mexico and into Texas by Wednesday.  It will then lift north-northeast towards the Midwest on Thursday and weaken somewhat.

An upper-level low over central TX Wednesday evening will lift north-northeast by Thursday. The track is not particularly favorable for severe weather in the Mid-South.

As the upper-level low moves northeast, surface low pressure over Texas will begin to lift north during the same time frame.  A warm front extending east from the low will lift towards the region Wednesday, bringing increasing rain chances and the possibility of some thunder as it moves through the region Wednesday night. As the surface low moves northeast Thursday, it will drag a cold front through the Mid-South.  The cold front will encounter unseasonably warm and moist Gulf of Mexico air in place over the region and thunderstorms will be a good bet, probably Thursday afternoon.

Precipitable water values Wednesday evening show high moisture content in the atmosphere ahead of the approaching weather system, meaning the possibility of heavy rain.

As low pressure in OK lifts northeast Thursday, the cold front entering western AR will move through and could bring a round of thunderstorms. The Mid-South will be in the "warm sector" behind the warm front all day.

Meanwhile, a warmer pattern will begin to take hold this week and will be augmented by the arrival of the Gulf airmass.  While temps will approach 60 on Tuesday and Wednesday, highs Thursday ahead of the cold front could reach 70. Behind the front, the airmass moving in will be of Pacific (not Canadian) origin, so mild temperatures will continue on Friday, which may also see highs approach 70.  Another system will move in for the weekend, bringing high rain chances once again.  Much cooler temperatures will trail that system as we end the weekend and start next week.

While the threat of severe weather does not look particularly high on Thursday, an isolated severe storm cannot be ruled out, with damaging wind being the most likely threat it appears.  Any storms on Wednesday or Wednesday night would be "elevated" in nature (meaning the lift within the storms does not originate at the Earth's surface), so thunder and lightning will be possible, but the severe weather risk is very low.  The main concern with both systems in the coming week will be heavy rain. And considering the lack of rainfall over the past several months, this may not be a bad thing. Rainfall totals of 2-3" are very possible with the mid-week system while another couple of inches is definitely possible this weekend.

Projected 7-day rainfall amounts through Monday, January 14. The Mid-South could see 4-6" rainfall totals from the next two weather systems.

We'll keep you updated as the week goes along.  Follow MWN on Facebook and Twitter for the latest info and download our  iPhone or Android app for the most recent forecast and always-current StormView Radar, as well as severe weather warnings for the location(s) nationwide that YOU are most concerned about.  Our complete forecast can be found here on MemphisWeather.net.

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Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
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December 2012 Climate Data and Forecast Accuracy

Temperatures once again averaged well above normal, while precipitation was below normal, with the year ending in the top 10 driest on record.  Drought conditions continued to abate, even though rainfall was below normal. Most of the Memphis metro is now classified as being "abnormally dry," which northern Shelby and Tipton Counties are still in a moderate drought.  The month also saw the first snowfall of 2012-2013 winter with about an inch in most areas of the metro (slightly more north and less south) beginning around midnight Christmas night and lasting into the morning hours of the 26th.

In addition, there was one severe weather event, on December 9th, which produced hail reports in the metro and strong wind gusts.  Year-end statistics will be reported in a separate blog post, but the average Memphis temperature for 2012 set a record for the warmest on record, averaging 66.0 degrees, 0.4 degrees warmer than the previous record high set in 2007.

Memphis International Airport, Memphis, TN

The average temperature for the month of December was 49.8 degrees, or 6.2 degrees above normal, which ranks as the 8th warmest December on record. The average high temperature was 58.0 degrees and the average low was 41.5. The coolest temperature of the month was 21 degrees on the 30th, while the highest temperature was 75 degrees on the 3rd, which also tied a record high for the date. There were 9 days on which the low temperature fell to freezing or below.

Precipitation for the month totaled 3.73", which was 2.01" below average. There were 17 calendar days with measurable rainfall, but only 3 saw totals of 0.50" or more (maximum 0.92" on the 9th-10th). Snowfall from the December 26th winter storm produced 0.9".  The peak wind gust was 47 mph from the west on the 20th with an average wind speed for the month of 8.5 mph. Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions, Bartlett, TN

The average December temperature at Cirrus Weather Solutions was 48.2 degrees (0.1 degrees warmer than November) with a maximum of 75.1 degrees on the 3rd and a minimum of 18.4 degrees on the 30th. December precipitation measured 4.36" via the Cirrus automated gauge and 4.35" in a manual gauge used for the CoCoRaHS program (which included about 0.10" that fell in the early morning hours on January 1). Snowfall on December 26 totaled 1.3".  The measured peak wind gust was 34 mph on the 20th. Average relative humidity was 80%. Click here for a daily recap on MemphisWeather.net.

MWN Forecast Accuracy

For the month of December, the average temperature error in all MWN temperature forecasts was 2.37 degrees, lower than all available full-range computer model data and the National Weather Service. More than 65% of the MWN temperature forecasts for the month were within 2 degrees of the actual temperature. MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). For dewpoint accuracy, the MWN forecast averaged 2.70 degrees of error and fell within 2 degrees of the actual dewpoint nearly 55% of the time. Historical accuracy statistics can be found here.

For the year, the average temperature error in all MWN temperature forecasts was 2.22 degrees. 66.8% of the MWN temperature forecasts for the month were within 2 degrees of the actual temperature. For dewpoint accuracy, the MWN forecast averaged 2.65 degrees of error and fell within 2 degrees of the actual dewpoint over 59% of the time.

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Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring a fresh new interface and StormWatch+ severe weather alerts!
Nowcasting services available on our Facebook page and Twitter feed.