Tuesday, December 30, 2014

New Year's Eve forecast and a chance of wintry weather Thursday night [VIDEO]

Wrapping up 2014 with a brief look at temps and precip for the past year, the discussing COLD conditions for your New Year's Eve and New Year's Day as well as an overrunning precipitation event on Thursday night that could mean a chance of wintry weather for a short period.

Bottom line

Very cold conditions expected through Thursday with Arctic high pressure in control. Wind chills in the teens are expected overnight and in the 20s all day tomorrow. New Year's Eve festivities tomorrow will require a heavy coat as temps drop back into the 20s.

Precipitation ahead of our next system breaks out Thursday late afternoon or evening as light rain, possibly mixed with a bit of sleet for a few hours until the atmosphere moistens up. All rain expected after midnight (early Friday) and continuing, periodically heavy, through Saturday with temps remaining above freezing. Thunderstorms are also possible Saturday depending on the track of low pressure.

Thanks so much to all of our followers and friends for a phenomenal 2014! We can't adequately express our gratitude through a blog, but know that your amazing support is what will keep us going into what should be a fantastic 2015!

Watch for an update to this blog on Thursday morning with the latest on possible winter weather and follow us on social media for any changes in the meantime

Erik Proseus
MWN Meteorologist

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Saturday, December 27, 2014

A wet weekend leads to a dry and cold week as 2015 arrives

We hope that everyone had a great Christmas and are thankful that rain held off to make for very pleasant weather for the holiday! Rain has moved in today though as a cold front approaches and moisture surges in from the Gulf. The front will pass through early this evening and bring temps down from the tolerable mid 50's quickly into the 40's. The cold front won't stop the rain though, as it continues overnight and into Sunday morning as low pressure moves along the front, wrapping rain back into the metro. Sunday will be much cooler behind the front with temperatures fairly steady in the mid 40s, or about 10 degrees cooler than today.

What temperatures could look like tonight at 9 PM as the cold front pushes through the metro. Graphic courtesy WeatherBell Analytics.
By noon on Sunday most rain will be out of the metro, with some lingering showers left over in northern Mississippi departing toward the east as yet another low moves along the front. This will effectively end precipitation chances in the metro until after New Year's Day. Cool but dry conditions are expected for those of you heading to the Liberty Bowl to see Texas A&M take on WVU.

Simulated radar at noon Sunday, showing what's left of rain departing to our east. Graphic courtesy WeatherBell Analytics.

Temps in the meantime look to get quite cold with temps in the lower 40's for highs and the upper 20's for lows on both New Year's Eve and New Year's Day as massive Arctic high pressure moves into the western U.S., but "leaks" east across the Plains into the Mississippi Valley.

Temperatures could be more than 10 degrees below normal as we prepare to ring in the New Year. Graphic courtesy WeatherBell Analytics.
Looking ahead to Thursday night, precipitation will make its return from the south, while temperatures at the onset could be right around freezing as lingering cold air hangs around. It's too early to make a call with any certainty, but initial precipitation Thursday night into early Friday could fall as light ice or snow. However we expect precipitation to change over to rain during the day Friday as warmer temperatures stream into the region from the south. Rain could continue into the weekend for those of you with any plans for the first weekend of the 2015. 

Here's a look at the full MWN 6-Day Forecast:

We'll keep everyone updated on the latest conditions and expectations heading towards the Liberty Bowl and New Year's Eve on our social media channels listed below.

William Churchill, MWN Social Media Intern

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Wednesday, December 17, 2014

First look ahead to Christmas weather in the Mid-South

Everybody and his cousin  (who lives in the Memphis area) are inquiring minds and want to know: "Are we going to get a White Christmas??"  I'll answer that 2 ways. First, read this excellent blog post MWN intern Kevin put together a couple of days ago. Historically speaking, it's highly unlikely. But that's not the answer you want a week out. So here is our first "official" look at holiday weather, using actual forecast data.

We first have to get through the next several days, which bring us a couple of rounds of precipitation - the first one overnight tonight and another Friday afternoon and night. Sunday and Monday look pleasant with increasing temperatures (50 Sunday, mid 50s Monday), then the next weather system arrives Tuesday the 23rd with a good chance of rain.

Tuesday's system should clear out by Wednesday morning, so Christmas Eve looks to be  windy chilly but likely dry. Right now we're calling for temperatures in the 40s with partly sunny skies and gusty north wind. In fact, to our north, a huge low pressure system is being predicted by multiple long-term models to be over the Great Lakes region with  impacts across a wide expanse from the Northeast to the Tennessee and Mid/Upper Mississippi Valleys (see GFS model solution below). This system will be responsible for our wind and could get a few snow showers as close as middle TN on Christmas Eve.  If you have travel plans, particularly by air, north and east of Memphis on Christmas Eve, this system could cause all kinds of delays.

GFS forecast surface map and precip type late Christmas Eve. A "mega-low" over the Great Lakes region would have ea large sphere of influence over the eastern half of the country. Graphic courtesy WeatherBell Analytics.

As for Christmas Day, as the large low pressure system to our north moves slowly into southeast Canada, it's influence on the Mid-South will lessen and high pressure will build in. Therefore, as of this minute, I expect an "average" Christmas Day with cool and dry conditions. Of course, things can still change rapidly between now and then and details are yet to be ironed out.

Experimental GFS modeled temps and precip for the next 10 days. This is NOT a forecast, just one possible solution. Days are listed near the bottom from left to right, temps are the red/black lines and rain amounts are the blue bars. Graphic courtesy WeatherBell Analytics.

So while we may not have the White Christmas you would like, hope is not lost! The same models showing the mega-low are showing a rapid warm-up to end Christmas week, but beginning the last weekend of the year in to early January, signs are pointing towards a general cool-down. Perhaps we can get some moisture to work its way into below average temperatures and bring some snow for early 2015! No bets on that this far out though!

We'll continue to keep you updated on our latest thinking on our social media channels below and will update the blog again as needed.

Erik Proseus
MWN Meteorologist

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Monday, December 15, 2014

A warm start to a chilly week with periods of wet weather

Yesterday was a great December day with temps in the mid 60s and lots of sunshine. Despite off and on rain, it's also a mild day today as the rain out-raced the cold front, so warm Gulf air continues to flow into the region as the cold front lingers to our west. The front will move through late this afternoon however, bringing an end to the 60s for the foreseeable future. This was just the first in a series of weather systems to affect the region this week.

Tuesday and Wednesday will be "tweener" days as high pressure briefly takes over following today's front and our next weather system affects the region Wednesday night. Colder air will filter in behind tonight's front bringing highs Tuesday back down to near normal in the 50s. Lows will drop to near freezing Wednesday morning and clouds will increase during the day, holding temperatures down in the 40s for the daytime hours.

Forecast mid-level pressure (500mb or ~18,000') Wednesday morning indicating a flat ridge over the southern U.S. Graphic courtesy WeatherBell Analytics.

The pattern shift that persists through the end of the week begins Wednesday night as moisture rides up into the area on west-southwesterly wind flow, bringing a period of light precipitation - the second weather system of the week. Right now, it appears temperatures will remain above freezing all night with lows in the mid 30s. This scenario bears watching though in case surface temps trend any colder. The most likely precipitation type if NOT rain will be light freezing rain. Again, ice is not currently in the forecast.

GFS forecast precipitation amounts from midnight through 6am Thursday as moisture and precip arrive from the west. Amounts range from 0.25-0.50". Graphic courtesy WeatherBell Analytics.

GFS forecast temps at 6am Thursday, indicating mid 30s across the metro. Graphic courtesy WeatherBell Analytics.

Very light precipitation is possible again on Thursday and Thursday night with cloudy skies and cool temperatures. The last weather system of the week arrives early Friday as low pressure develops over Texas and moves east. Odds are that this low will bring a fair amount of rain Friday into early Saturday as it travels by to our south. Amounts of 1-2" are possible. There are signs from one medium-range computer model (the European) that there could be enough cold air filtering in on the backside of the low Friday night to POSSIBLY change rain over to light snow. However, none of the other models depict this same scenario as of now. In fact, the European model became much less bullish with snow in this morning's data, so confidence increases in a relatively warmer solution (but still cold for those who will be out in the elements!).

As always, there are many factors that will affect the eventual outcome, including strength and track of the low and resultant amount of cold air that moves in and how quickly it does so. We are carrying RAIN in the forecast but continue to monitor. We're hopeful for a mainly dry, but chilly, weekend as the season officially changes from autumn to winter Sunday evening. Also, looking ahead, it currently looks dry and cool for the Autozone Liberty Bowl next Monday (40s).

Farther out (too far if it were any day but Christmas), long-range models are pointing to one more southern stream system around Tuesday/Wednesday similar to this Friday's, then a chilly Christmas Day that looks dry. We'll update again in a few days with the latest thinking and be sure to follow us on social media for any updates. Also, be looking for a blog later tonight on the history of Christmas Day weather in Memphis! Hint: it doesn't bode well climatologically for a white holiday.

Erik Proseus
MWN Meteorologist

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Monday, December 8, 2014

November 2014 Climate Data and Forecast Accuracy

November Recap

November was a cold and dry month across the Mid-South. In fact, the month tied for the 7th coldest on record. The cold also led to some of the earliest snowfall on record with two measurable events - the 4th and 7th earliest on record. Though it was a cold month, for the months of September-November (defined as meteorological fall), the average temperature was just 1.2 degrees below normal due to slightly above normal temps in September and October. Precipitation for the same three-month period was 1.25" below average at 11.31". There was no severe weather during November.

Memphis International Airport, Memphis, TN

Average temperature: 47.4 degrees (5.8 degrees below average)
Average high temperature: 56.5 degrees
Average low temperature: 38.2 degrees
Warmest temperature: 75 degrees (4th)
Coolest temperature: 20 degrees (18th)
Records set or tied: Record warmest low temperature - 61 on the 30th
Comments: November 2014 ranked as the 7th coldest November on record (since 1875). Ten days saw temperatures fall below 32, which is 7 above normal. For the year, the average temperature at Memphis is 62.6 degrees, which is 2.1 degrees below average.

Monthly total: 2.56" (2.93" below average)
Days with measurable precipitation: 8
Wettest 24-hour period: 1.46" (4th-5th)
Total Snowfall: 0.2" (0.2" above average)
Records set or tied: None
Comments: Measurable snow fell on two days in November (0.1" each), which marked the 4th and 7th earliest measurable snowfalls on record. Only two days had precipitation above 0.50". As of the end of November, the yearly precipitation has been 55.03", which is 7.09" above (or 115% of) average.

Peak wind: South/43 mph (30th)
Average wind: 8.5 mph
Average relative humidity: 61%
Average sky cover: 50%

Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions / MemphisWeather.net, Bartlett, TN

Average temperature: 45.9 degrees
Average high temperature: 56.1 degrees
Average low temperature: 35.5 degrees
Warmest temperature: 74.6 degrees (4th)
Coolest temperature: 19.1 degrees (18th)
Comments: None

Monthly total: 2.81" (automated rain gauge), 2.86" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 11
Wettest date: 1.13" (5th) (via automated gauge)
Comments: None

Peak wind: Southwest/30 mph (29th)
Average relative humidity: 73%

Click here for a daily statistical recap for Bartlett, TN.

MWN Forecast Accuracy

MWN average temperature error: 2.51 degrees
MWN forecast temperatures within 2 degrees of actual: 59%
MWN average dewpoint error: 2.34 degrees
MWN forecast dewpoints within 2 degrees of actual: 65%

MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). Historical accuracy statistics can be found here.

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Ridges and troughs: signs of fluctuating temperatures this week

It was a rather pleasant early December day in the Mid-South, but don't get too comfortable as changes come quickly. It's the time of year that variations in the weather pattern can come frequently and we have a classic pattern setting up that favors quick swings in temperature as the atmosphere tries to figure out what season it is.

The Mid-South will get wedged between an upper level trough (or lower pressure) to our east and an upper level ridge (or higher pressure) to our west for most of the work week. This will result in what is called "northwest flow" for the area, in which the upper level flow of air is from northwest to southeast. This pattern is usually quite progressive, resulting in large oscillations in temperatures due to frontal passages and increased precipitation. In this case though, the pattern looks a lot drier, with a shortwave embedded in the flow only able to bring cloud cover (and perhaps a few sprinkles) to Memphis Wednesday into Wednesday night.

Upper level map showing height anomalies, indicative of ridges and troughs.
The Mid-South wedged in between the two, resulting in northwest flow.
Now, lets talk about those temperatures swings. First we'll start with a cold front that is coming through the Mid-South tonight, which is associated with a weak upper-level trough that makes its way through the area and then strengthens to our east, thus strengthening the northwest flow. This will bring cooler temps south for the next couple of days, resulting in lows near freezing Wednesday morning and highs in the mid to upper 40's for the middle part of the work week.

Surface temperature anomalies Wednesday morning showing temperatures about 8 degrees below average for the Mid-South.
These below average temps won't stick around too long though, with a building upper level ridge to our west that will slowly make its way into the Mid-South. We'll start feeling the effects of that ridge by Friday as above average temps settle in for the weekend (high temps in upper 50's and lower 60's).

Surface temperature anomalies during the day on Saturday. A drastic difference just 3 days after the previous map.
Looking into the longer range, there is fair agreement that temps will stay above average heading into next week. The Climate Prediction Center agrees, with their probability forecasts showing upwards of a 50% chance of above average temps all the way through the 3rd week in December. This does not mean that we won't see periods of cold, just that above average temperatures are more likely for the majority of the time.
The Climate Prediction Center forecasting over a 50% probability
that we see above average temps from December 14th-18th (early next week).
Below are the expected highs and lows for this week and as always, you can get the full MemphisWeather.net forecast here. Also follow us on Facebook and Twitter for daily details on the forecast.

William Churchill
Social Media Intern

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Friday, December 5, 2014

Rain and thunder to end the week then a cloudy but dry weekend

Rain is moving into the metro this morning as the first of a couple impulses moves through the area and a warm front continues lifting north. Temperatures are already climbing towards the mid 60s ahead of the rain with dewpoints rising above 60, which means a very humid airmass for early December. I'll use simulated radar graphics from one of our best high-resolution models as we talk through the day.

Simulated radar from the HRRR model valid at noon.
Rain will last throughout the afternoon hours, meaning a wet dismissal from school this afternoon mostly likely. Some rumbles of thunder are possible this afternoon as well.

Simulated radar at 3pm. Rain and some thunder possible as kids get out of school.
The initial batch of rain looks to be moving out around rush hour tonight. and, if they're lucky, the Collierville Christmas Parade at 7pm MIGHT catch a break with just scattered showers and thunderstorms around. The parade is rain or shine, but if you're planning to attend, use common sense and seek shelter if you see lightning or hear thunder. [UPDATE: This afternoon, Collierville officials decided to cancel the parade. There is no makeup date.] This relative "lull" in activity could also coincide with the arrival of 18,000 of you at FedExForum tonight. (Go Grizz!)

Simulated radar at 6pm showing the initial batch of rain departing but more activity developing to the west.
By late evening into the early overnight hours, thunderstorms are looking more likely as a cold front draws closer and runs into very humid, warm air and sufficient wind aloft to allow for some storm organization. The Storm Prediction Center has placed the Mid-South in a Marginal risk for severe weather, which is category 1 of 5 and below a Slight Risk. The chance of severe weather is slim, but brief strong wind gusts are possible if strong wind aloft mixes down to the surface in thunderstorms.

Simulated radar at 10pm, projecting some thunderstorms in the area as a cold front nears.
A Marginal Risk of severe weather (category 1 of 5) exists for the Mid-South. Brief strong wind gusts are possible, but not likely, from evening into the overnight hours.
Overall, this will be a pretty good rainmaker with rainfall amounts over an inch likely to be common by Saturday morning and some spots possible seeing 2" if multiple storms move overhead.

Forecast rainfall totals from the National Weather Service through 6am Saturday.
The good news is that all of the rain should be gone by 6am Saturday with maybe just some drizzle or sprinkles Saturday morning. Temperatures in the morning will likely hover in the lower 50s during the morning with a steady north wind at 10-15 mph for the St. Jude Memphis Marathon.

For afternoon and early evening Christmas parades on Saturday, conditions should be dry but cloudy with that north wind still blowing and temperatures falling from around 50 at 3pm to the upper 40s by 7pm. A warm coat will be a good idea as the wind will be cool, but it won't be a frigid day with hand warmers, scarves and gloves probably not necessary.

No rain is in the forecast from Sunday through much of next week.  Click here to view the complete MWN Forecast and be sure to follow us on our social media feeds throughout the day and evening for the latest info (links below). Also check out our MWN mobile app for the latest metro radar, forecast, and Twitter updates, even if you don't use Twitter. We might just win you over. :-)

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!