Friday, November 17, 2017

A cold front that means business and an early look at Turkey Day

The weekend before Thanksgiving brings lots of activities across the area, not the least of which is a Memphis Tiger football game with conference championship implications at 11am Saturday, as well as the downtown Memphis Christmas tree lighting event and a Christmas event in Arlington later in the day. So what's this big cold front we've been heading about? Let's get into the details.

Friday Night

You have to know that gusty south wind and temperatures in the lower 70s in mid-November, like we have today, are typically followed by a dose of reality just around the corner. That is certainly the case this time, as a cold front is getting ready to barrel across the region on Saturday. Today is "prep day" with that south wind pushing higher dewpoints (aka, more moisture) into the Mid-South. The wind will pick up even further tonight as the front makes progress in our direction with southerly gusts that will exceed 30 mph and could approach 40 mph! That will keep temperatures mild overnight (in the 60s), though precipitation chances are very low.

Surface low pressure will be located in southern Kansas and heading towards the Ohio Valley tonight into Saturday. Overnight into Saturday morning, the low combines with high pressure to our east to bring gusty southerly wind to the area. (PivotalWx)


As low pressure in the Plains moves east-northeast across the Midwest/Ohio Valley on Saturday, a cold front will sweep across the Mid-South. Current ETA for Memphis is 1-2pm, but that could vary an hour either way.  Ahead of the front, the strong southerly wind will continue with temperatures rising to 70° by noon. If you're tailgating, it'll be short sleeve weather with tie-downs for your tents a MUST. In addition, a few scattered showers are possible in the morning but they should be brief as the cloud-level wind will be pushing them at nearly highway speeds (for those that don't speed...).

After lunchtime, and probably during the second half of the Tigers game, when Riley & Co. will be in the midst of raining touchdowns on SMU (Go Tigers!), the front will arrive at the speed of Tony Pollard's kickoff returns. You'll know when it hits, because it'll be marked by a sudden wind shift to the northwest, a brief period of potentially heavy rain, and possibly a rumble of thunder. The line of rain along the front looks to be narrow and fast-moving, so it may only last 10-15 minutes. Don the ponchos over the short-sleeve shirts, then be prepared to quickly add a sweatshirt layer once the rain ends! Once the quick-hitting rain ends, the wind turns cold and just as gusty (25-35 mph) and temperatures head down, tumbling quickly into the 50s.

The high-resolution NAM model from Friday morning shows scattered light showers Saturday morning (the beginning of the loop above) then a narrow line of heavy rain along the cold front by early afternoon. The latter half of the loop is Saturday afternoon into early evening and shows dry weather behind the front. (Tropical Tidbits)

The good news is that the rain threat ends once the front passes, mid to late afternoon and evening activities will be dry. Temperatures continue to fall into the upper 40s by tree lightning time downtown (5:30pm) and the blustery wind starts to let up, though will remain at 10-20 mph into the evening hours. If you have evening plans, think warm coats, not the shorts you had on in the morning!

As for a severe weather threat, the Storm Prediction Center currently has the metro on the edge of a "Marginal" (category 1 of 5) threat. There is meager instability ahead of the front and plenty of wind energy, so a brief wind gust to 60 mph is possible, though not likely, in the line that moves through along the front.

A Marginal Risk of a few severe wind gusts are predicted by the NWS for portions of the area in dark green. The thunderstorm threat, as well as severe threat, is very low (category 1 on the 5-point scale). (SPC)

The Tigers seemingly have been snake-bitten by weather events this year, but this event at least looks to be brief (outside of the sustained wind), so grab the poncho and #PackTheBowl for what promises to be a great football game! #StripeUp

The graph above shows temperature forecasts from several high-resolution models from tonight through Sunday. The black line is the model average. Note the very warm temps overnight, the large drop Sunday afternoon, and much cooler weather on Sunday, despite sunny skies. (NOAA)

Sunday and beyond

High pressure quickly builds in, making for a return to November-esque weather with highs generally in the 50s for Thanksgiving week and lows that could threaten freezing outside the city on Monday morning. A reinforcing shot of cool air arrives Tuesday night with freezing temperatures again possible Thanksgiving morning. Highs on Turkey Day will be cool - in the lower 50s most likely. Weather looks dry next week though, as any flies in the ointment that might bring precipitation stay well to our south in the Gulf.

Stay up to date with the latest conditions and forecast, as well as monitoring our Twitter and radar feeds, via the MWN mobile app. We appreciate your support of MWN in this small way, which pays big dividends for you!

Erik Proseus
MWN Meteorologist

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Thursday, November 9, 2017

Thoughts on the appearance of the sun and La Nina

Seven thoughts on a bright sunny day in Memphis...

1. It's been a while hasn't it? The sun came out in Memphis this morning, proof that it does still exist despite some folks expressing doubt over the past week!

Today is the first day since we went trick-or-treating that we've had an extended period of sunshine. Looking back through the hourly records from Memphis International Airport (link for weather geeks), there have been a few times after dark that skies have been clear since Halloween, but those don't count (no sunshine). During daylight hours, we've been partly cloudy for an hour or two here and there a couple times as well, but the overall character of each day since the calendar turned has been cloudy to mostly cloudy.

2. In fact, I had a feeling people wouldn't be ready for this rare event, so last night I issued a Bright Orb Warning. I hope it helped you adequately prepare!

3. It also occurred to me that tonight will be the first night we'll be able to fully experience a "Standard Time" sunset! It's gotten dark early this week, but at least today we'll have some daylight until the late, late hour of 5pm...

4. How long does the sun stick around? The MWN Forecast shows more sun than clouds through Saturday morning before some dense cirrus cloud cover arrives. We'll see a weak system move through Sunday that brings a chance of rain, but the sun should return Monday for a couple days. Another cold front arrives next Wednesday with slightly higher rain chances. Overall, we should be able to get used to seeing sunshine more days than not over the coming week.

5. How about temperatures? We'll call them "seasonal," which is pretty decent. Normal highs are in the mid 60s this time of year with lows in the mid 40s. After a reinforcing shot of cool air tomorrow, we should see numbers fairly close to that for the upcoming week. Friday will be chilly with highs only in the mid 50s and if you're up early Saturday morning, you'll need a coat if you head to the patio for coffee. Rural areas will be near freezing and everyone will be in the 30s. Layer up if you're running the Greenline Half or 5K at Shelby Farms!

6. Meanwhile, to our west, the National Weather Service (NWS) has officially declared that La Nina has begun (again) in the Pacific. We had a weak La Nina last winter, which then turned "neutral" earlier this year. The NWS calls this return to La Nina a "double dip." It will have effects on the winter ahead.

Red areas are places where the forecast odds favor a much warmer than usual winter, while blue colors favor cooler than usual winter. The darker the color, the higher the probability of that outcome (not a larger departure from average). NOAA map, based on data from NOAA CPC.

Brown areas are places where the forecast odds favor a much drier than usual winter, while blue-green colors favor wetter than usual winter. The darker the color, the higher the probability of that outcome (not a larger departure from average). NOAA map, based on data from NOAA CPC

7. Though I don't have an official "winter forecast" published, locally I expect we'll see a warmer than average winter season, but it could actually start cooler than average (late November into December). Mid to late-winter will likely be above average overall. While areas to our south (closer to the Gulf coast) will be drier than usual, I expect we will see a storm track that could favor some storminess as we sit in a "battleground" between warmer air in the south and pushes of cold air to our north. This setup could favor a winter weather scenario or two. I'm leaning more towards ice than snow, but that can't be predicted in this area more than a few days out, so why listen to me in November??

Enjoy the sunshine!

Erik Proseus
MWN Meteorologist

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Saturday, November 4, 2017

October 2017 Climate Data for Memphis, TN

October Climate Recap

Temperatures ended up slightly above average for the month, though the first half of the month featured more above average days, while the second half of the month saw more below average temperatures. In the early half of October, there were several days in the upper 80s and one day reached 92 degrees, which set a record for the date (9th). The tide turned at mid-month with more 60s and 70s, and even a couple of days with highs in the 50s and lows in the 30s. According to the National Weather Service, the low of 31 degrees on the 29th was the first sub-freezing low temperature in the month of October in 24 years!

Except for two days of the month, October was also dry. However that was offset by a 2.50" rain event on the 10th and another one inch-plus soaker on the 27th. Those two days totals over 90% of the monthly precipitation. The rain on the 10th was also not evenly distributed, as MWN's Bartlett weather station only recorded 0.41", thus ending the month well below normal. There was no severe weather for the month and no warnings issued.

Memphis International Airport, Memphis, TN

Average temperature: 65.2 degrees (1.1 degrees above average)
Average high temperature: 75.8 degrees (1.4 degrees above average)
Average low temperature: 54.6 degrees (0.8 degrees above average)
Warmest temperature: 92 degrees (9th)
Coolest temperature: 31 degrees (29th)
Heating Degrees Days: 128 (8 above average)
Cooling Degree Days: 143 (51 above average)
Records set or tied: Record warm minimum temperature tied on the 8th (72 degrees). Record high temperature set on the 9th (92 degrees).
Comments: Year to date, the average temperature of 68.0° is tied for the fourth warmest on record.

Monthly total: 4.04" (0.06" above average)
Days with measurable precipitation: 7
Wettest 24-hour period: 2.50" (10th)
Snowfall: None
Records set or tied: 2.50" of rain on the 10th was the second wettest October 10th on record.
Comments:  Only two days recorded precipitation of more than one-half inch, however those dates accounted for 91% of the rain total for the month. Year to date, precipitation has totaled 42.31" or 99.7% of normal (average year-to-date: 42.45").

Peak wind: Northwest/32 mph (24th)
Average wind: 7.9 mph
Average relative humidity: 64%
Average sky cover: 40%

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

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 62.9 degrees
Average high temperature: 76.5 degrees
Average low temperature: 50.5 degrees
Warmest temperature: 91.9 degrees (9th)
Coolest temperature: 27.2 degrees (29th)
Comments: None

Monthly total: 1.74" (automated rain gauge), 1.69" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 8
Wettest date: 0.74" (27th) (via automated gauge)
Snowfall: None
Comments: None

Peak wind: Northwest/22 mph (15th)
Average relative humidity: 76%
Average barometric pressure: 30.07 in. Hg
Comments: None

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

MWN Forecast Accuracy

MWN average temperature error: 1.89 degrees
MWN forecast temperatures within 2 degrees of actual: 70%
MWN average dewpoint error: 1.79 degrees
MWN forecast dewpoints within 2 degrees of actual: 73%

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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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder