With flurries and clouds moving out into early evening and high pressure nearby tomorrow, our main forecast concern in the week ahead is with a late week system. A potpourri of precipitation types (snow, rain, sleet, and freezing rain) are forecast in the Ohio Valley Thursday night.

This will be a tricky forecast, especially with a lack of consensus among models. With a lack of consensus, it is not worthwhile to make a specific county-by-county ice accumulation forecast. We are also more than 48 hours out on this event, supporting the idea that now is not the time to go into specifics.

My focus for this blog post will be on output from the SPC Short Range Ensemble Forecast (SREF) model. The word “ensemble” in meteorology refers to a series of models that are run with different initial conditions; if models with different initial conditions are in good consensus on a particular forecast, confidence is higher than average that particular forecast will verify. Looking at the mean of the SREF models helps to weed out extreme model forecasts.

This morning’s SPC SREF run gives the Tri-State between a 30% and 90% chance (depending on where you live) of measurable ice accumulation between 10pm Thursday and 1am Friday:

This morning’s SPC SREF gives the Tri-State a roughly 40% chance that we get at least 0.05″ of freezing rain accumulation (at least a light glaze) between 10pm Thursday and 1am Friday:

NOAA’s Hydrometeorological Prediction Center gives most of the Tri-State a 10% chance of 1/4″ of ice accumulation or more Thursday night and early Friday:

1/4″ of ice accumulation serves as a rough milestone for where power lines start to sag or may fall completely to the ground. 1/8″ of ice will lead to some slick roads and sidewalks

This morning’s GFS model gives Cincinnati about 0.2″ and Wilmington about 0.15″ of ice accumulation Thursday night; likewise, this morning’s NAM model gives Cincinnati about 0.15″ and Wilmington about 0.1″ of ice accumulation Thursday night. Again, these are what two models are projecting and is NOT a forecast. I share these totals with you to show that this is not going to be a major ice event but may be more than a nuisance.

What To Expect Thursday Night

Confidence is high that sleet, rain, snow, and freezing rain will overspread the Ohio Valley Thursday evening. Precipitation will likely start as a mix of rain, snow, and freezing rain in Cincinnati with temperatures around freezing. Nearing 12am Friday, the mix of snow, rain, and freezing rain will transition to a rain and freezing rain mix…with a small chance for sleet also. By sunrise on Friday, most – if not all – of the Tri-State will see rain with some freezing rain and sleet mixing in north of Cincinnati.

Right now, I’m thinking some in the Tri-State see a light glaze of ice, especially north of the Ohio River. Temperatures will be in the lower 30s nearing all of Thursday evening; the temperature is forecast rise 1-3° between 10pm Thursday and 7am Friday, which works against the idea of ice accumulation.

A 1-2° change in temperatures Thursday night may have a significant impact on what type of precipitation you see and how much ice you see. It is better to start conservative on an ice forecast and ramp up if needed than to go the other way.

Stay tuned for an update tomorrow!

A strong cold front will sweep through the Tri-State early tomorrow morning, bringing rain this evening, a rain/snow mix overnight, and flurries tomorrow afternoon. Mid-week will be quiet, but another system coming later this week looks to bring the Ohio Valley a mess of rain, snow, sleet, and freezing rain.

Everyone will see light rain tonight; some may see brief moderate to heavy rain. By the time this system pushes east tomorrow night, Precisioncast gives us roughly 1/2″ of precipitation (nearly all of this will be rain):

The higher-resolution Microcast run from this morning gives us about a 1/2″ of precipitation through tomorrow night as well:

Besides Microcast and Precisioncast, the three major forecast models we use in the weather center give us anywhere between 0.19″ and almost 0.6″ of precipitation (mostly rain) through tomorrow night:

By tomorrow afternoon, we should only have flurries in the area with temperatures nearly steady in the low to mid 30s.

The weather system that is coming later this week looks more interesting and has my attention. A mix of rain, snow, sleet, and freezing rain is likely coming late Thursday and early Friday. The NAM model’s simulated radar product from this morning suggests we’ll see rain over ice by 7pm Thursday night, but I’m skeptical:

The latest run of the GFS model gives Cincinnati about 0.2″ of ice Thursday night and early Friday. Here’s a map of forecast ice accumulation this morning’s GFS model (through 7pm Friday):

Recent runs of the GFS model have given Cincinnati about 0.1 to 0.2″ of ice accumulation. This is not enough ice to bring down power lines, but it’s enough to make the roads slick. A difference of 2° in the temperature near or above the ground will make a big difference on how much rain, snow, ice, or sleet we get.

Confidence is high that much colder air is coming for Friday, Saturday, and Sunday. There is, however, some uncertainty on how much moisture will be embedded in this cold air nearing the weekend. The upper-level and surface support for flurries and snow showers is there, but how much upper-level and surface support we get remains in question.

The latest run of Microcast has snow showers and flurries in the area tomorrow, as do most forecast models. Microcast suggests we will see little to no snow accumulation from tomorrow morning through Friday night:

Nearly all models struggle with finer details, including specific snow amounts. I suspect there will be some instability in the area tomorrow, so quick bursts of snow are more likely than a large swath of snow in any given part of the Tri-State. You can see hints of these isolated pockets of heavier snow around Cincinnati in this afternoon’s NAM model snow output (through 7am Saturday):

You can also see the isolated, heavier bursts of snow in this morning’s higher-resolution NAM model snow output (through 7am Saturday):

For now, Friday’s forecast calls for little to no accumulation for most, but there will be some localized bursts or bands of heavier snow. These small pockets of heavier snow may produce up to 1″ of accumulation. Of course, it is hard to predict where these small-scale features will set up, especially more than 12 hours out.

In addition to snow, we are also tracking the return of cold air for Friday, Saturday, and Sunday. This morning’s ECMWF model shows cold air (in blue and purple) diving south into the Great Lakes and Ohio Valley by 8am Saturday:

While it will be cold this weekend, the latest ECMWF model suggests the jet stream will push back to the north, and warmer air (in orange and red colors) will push back into the Tri-State by 8am Monday morning:

This warm-up will be temporary. A cold front will likely sweep through early Tuesday, bringing the return of cold air and snow by Tuesday afternoon.

We love to hate snow in Cincinnati. Through this date last year, only 3.6″ of snow had fallen in Cincinnati. Since September, over 15″ of snow has fallen in the Queen City. Despite this being a warmer than average winter (so far), we will likely see a near average amount of snow for fall, winter, and spring as a whole:

Ever since late last week, we have been discussing the possibility of a rain/snow mix for Wednesday. Some models suggest precipitation tomorrow will be all snow, others suggest it will be a rain/snow mix, and a few say most if not all of the precipitation we get tomorrow will fall as rain.

This will be a tricky forecast because temperatures will likely be near or just above freezing most of tomorrow morning and into parts of Wednesday afternoon. Powdery snow is unlikely Wednesday; in the areas that get snow, it will be very wet and slushy.

Model guidance continues to have the best chance for precipitation south and east of Cincinnati tomorrow morning and afternoon. By late tomorrow afternoon, this slug of moisture will be pushing east in a hurry.

So how much snow are we going to get? The latest run of Precisioncast gives parts of Ohio and Kentucky up to 3/4″ of snow through tomorrow evening:

This morning’s Microcast run is slightly more aggressive with snow amounts south and southeast of Cincinnati:

If you believe this morning’s ECMWF model, most are getting snow tomorrow in southwest Ohio and northern Kentucky:

NAM and GFS runs from this morning give areas south and east of Cincinnati snow, and little to no accumulation elsewhere. This morning’s NAM run gives the far southeastern corner of the Tri-State 1-2″ of snow through Wednesday evening and little to no snow in downtown Cincinnati. This morning’s GFS gives the Tri-State little to no snow tomorrow.

Forecast

I think areas south and southeast east of Cincinnati get up to 0.5″ of wet, slushy snow Wednesday morning and afternoon. A lot of this snow will melt on contact, especially on the roads. Surface pavement temperatures in Kentucky and southwestern Ohio are in the 40s and 50s now; while these temperatures will likely drop some overnight, it will likely be too warm for snow to stick on the roads in most places- especially treated roads – tomorrow morning and afternoon. Air temperatures will also be above freezing most of tomorrow morning and afternoon, working against the possibility for accumulation.

I’ll look over evening model data and update the forecast as needed!

The temperature has been nearly steady all morning and afternoon in Cincinnati, but the temperature will be fluctuating quite a bit in the next 10 days as the jet stream moves south and retreats back to the north.

For now, the jet stream is to our north; it will likely stay to our north through tomorrow. The latest GFS model has abnormally warm temperatures (in the orange and red colors) in the Ohio Valley at 1pm tomorrow afternoon:

On Wednesday, however, the latest ECMWF model suggests the jet stream will dip to the south, bringing slightly cooler air to the region:

This dip in the jet stream will temporary; the jet stream will push back to the north by Thursday. The latest GFS model shows above average temperatures (in orange and red) surging north into the Tri-State with the jet stream retreating back into southern Canada:

This change in the jet stream, too, will be temporary; the jet stream will once again push south this weekend, as the latest ECMWF model shows by Saturday night:

This morning’s GFS model shows abnormally cold air (shown in blue, green, white, and purple) aloft by 7pm Saturday night:

This cold air aloft will likely support a chance for flurries Saturday, Saturday night, and early Sunday.

While the weekend will be chilly, near or above average high temperatures will likely return by Tuesday. The latest GFS model has above average warmth in the Tri-State  early Tuesday morning:

Winter is not over! This up-and-down pattern will likely continue for the rest of February and into early March…

A winter storm with the potential for embedded blizzard conditions is now moving up the Atlantic coast of the United States. Very heavy snow is likely over most of New England today and tomorrow. Thousands of flights out of Boston, New York, and other airports in the northeastern U.S. have either been canceled or delayed as a result of this potentially historic storm.

This afternoon’s WRF model run gives most of Massachusetts, Connecticut, and Rhode Island 15-30″ of snow through 7am Sunday:

This afternoon’s higher-resolution WRF model gives 2’+ of snow to the Boston area by 1am Sunday:

This morning’s GFS model is more conservative with snowfall totals through 7am Sunday but still gives most of New England 10-20″ of snow:

Precisioncast, our in-house model, paints 2’+ of snow through the the weekend in and around Boston:

Blizzard Warnings, Winter Storm Warnings, and Winter Weather Advisories cover all of New England and parts of the Mid-Atlantic:

Why is so much attention being given to this winter storm? The simple answer is it will likely be historic. 27.5″ is the most amount of snow Boston has seen from a single storm (February 16-18, 2003). Many near Boston will likely see 2’+ of snow for the entire event. Compare that to our snowiest winter on record in Cincinnati (January 1978):

Travel is highly discouraged or temporarily against the law in parts of Massachusetts, Connecticut, and Rhode Island. This storm will make headlines!

The top story on the national news this weekend will be a nor’easter pounding New England and the Mid-Atlantic with heavy snow. Models have been reasonably consistent on giving the Boston area at least a foot of snow from Friday through Sunday, but some models are more aggressive than others.

So what’s the latest thinking on how much snow Massachusetts, Connecticut, Maine, New York, New Hampshire, and Vermont are going to get? Let’s start with the snowfall forecast from this morning’s NAM model (through 7am Sunday morning):

The NAM model says most will get 10-20″ of snow, and some (in the shades of white and dark green) will see 30-40″ of storm total snowfall accumulation. A higher-resolution of this morning’s NAM model run shows similar amounts of snow, but with some higher totals in New Hampshire:

Next up is last night’s GFS model snowfall forecast (through 7am Sunday):

The GFS is clearly not as aggressive with snowfall totals; it gives most of New England 2-10″ of snow with 10-20″ for eastern Massachusetts and downwind of Lake Ontario and Erie. What does last night’s ECMWF think for snowfall amounts Friday through Sunday? Here’s your answer:

Essentially, the ECMWF model is a blend of the latest GFS and the NAM model runs; the ECMWF gives most of New England 2-10″ of snow and the Boston area 20-30″ of snow.

WSI’s RPM model from 7am this morning gives most of New England 5-15″ of snow and areas close to the coast 2’+:

The 4am run of the RPM model looks similar, but different enough to give New England forecasters something to think about:

It is worth noting the the NAM, GFS, and ECMWF maps above assume a 10:1 snow-to-liquid ratio. In other words, the snowfall charts are made with the assumption that 0.1″ of liquid output from the models is equal to 1.5″ of snow in the same spot. This is a low-end approximation for this scenario. Models suggest snow-to-liquid ratios will be closer 15:1 or even 20:1 in spots Friday, Saturday, and early Sunday. This means that the snowfall maps above may be underdoing the amount of snow in spots this weekend.

Analogs (comparing this system to others in the past) suggests most of New England is likely going to get 12-24″ of snow. One of the strongest analogs to this upcoming event is the February 12, 1983 blizzard…which turned New York City into this: http://youtu.be/U9LiWVXpqg4

I don’t envy meteorologists making localized snowfall forecasts for the Mid-Atlantic and New England. This will be a tough forecast. This storm has the potential to be historic not only for snow amounts but also for it’s minimum pressure (how deep the center of low pressure gets). I wish forecasters along the East Coast the best of luck with this one!

Yesterday evening in the weather center, it became very clear that stratus clouds moving in from the north were moving our way, and those clouds were going to be tough to shake today. Why did the forecast need to be adjusted from thinking earlier this week? The answer comes from an understanding in how the temperature changes going away from the ground.

In meteorology, we learn what is going on in the upper-levels of the atmosphere by launching weather balloons across the county. One of those balloons was launched this morning at the National Weather Service forecast office in Wilmington. Meteorologists see wind, temperature, and dewpoint trends from the ground to the upper-levels of the atmosphere on a diagram called a Skew-T. This is the Skew-T from Wilmington from 7am this morning:

Unless you’re a weather aficionado, you may not be able to make sense of much of much on this diagram. The black line at the bottom of the plot represents the ground and the top of the plot represents the upper-levels of the atmosphere. The red line is the temperature, the green line is the dewpoint, and the black lines in a row on the right side of the plot represent the wind direction and speed. Let’s simplify it…and just look at the temperature in Wilmington at the ground and aloft around 7am this morning:

In the graph above, you can see the temperature rise and fall between the ground and 18,000 feet above the ground. Usually, the temperature decreases going away from the ground. In this morning’s case, we see temperatures decrease rising from the ground to 5,000 feet up. Between 10,000 and 15,000 feet above the ground, the temperature increases. In meteorology, this is called a temperature inversion:

A temperature inversion is another way of saying there is a layer of stable air above the ground. When clouds are trapped below this layer of stable air, they are often slow (and in some cases, very slow) to mix with drier air in the atmosphere, including above the temperature inversion:

As of 3:45pm, this temperature inversion is holding tough, and clouds persist in and around Cincinnati, while ample sun is found over most of central and eastern Kentucky:

These temperature inversions make forecasting the weather tricky. A difference of 1-3° in  the temperature at any given point above the ground can make the difference between quick clearing and slow clearing. Little to no clearing is forecast through mid-evening.

Two disturbances will push through the Ohio Valley between now and midnight; the first will move through over the next couple of hours, and the second will move through later this evening. A satellite and radar snapshot as of 3:55pm shows these two pieces of upper-level energy approaching the Cincinnati area:

The latest HRRR model’s forecast radar product has flurries favored northeast of the Tri-State around 9pm tonight:

Only flurries are forecast in the Tri-State this evening; little to no accumulation is forecast in and around the Tri-State. The latest run of Precisioncast gives no Tri-State community accumulating snow through tomorrow morning:

The latest run of Microcast gives us little to no accumulation through tomorrow morning:

Fog and dense fog will be a concern tomorrow morning. Visibilities in spots may be under a 1/2 or even 1/4 of a mile. Once the fog dissipates, ample sunshine is forecast Wednesday. Clouds will increase tomorrow night and Thursday, and a line of showers will sweep through Thursday night and early Friday. The best chance for rain in the next week will be late Sunday and Monday.

While rain will come and go in the week ahead, near or above average temperatures are forecast through the weekend. This morning’s ECMWF model has warm air surging into the Ohio Valley ahead of Thursday night’s cold front:

We should make it into the 50s Thursday afternoon. Some colder air will swing into the Ohio Valley Friday and Saturday (highs will be 40-45° each day), but warmth returns to the Tri-State by Sunday night and early Monday:

Temperatures will likely each into the 50s both Sunday and Monday afternoon. The latest ECMWF and GFS models bring another shot of cold air into the Tri-State by Tuesday or Wednesday next week.

The Cincinnati area remains under a SLIGHT risk for severe storms late tonight and early Wednesday; the Storm Prediction Center has placed the southwestern Ohio Valley, the southeastern Mississippi Valley, and much of the Mid-South under a MODERATE risk for severe storms tonight and early Wednesday:

This morning’s model runs suggests damaging straight-line winds will be the main severe weather threat in the Tri-State early tomorrow. A line of showers and thunderstorms has already formed over the Mississippi Valley and southern Plains; this line will be pushing east through the night and tomorrow. The latest high-resolution WRF model has a squall line along the Wabash and Mississippi River at 1am tonight:

By 7am, the WRF has the squall line (and perhaps a secondary line showers and thunderstorms) moving the Tri-State:

By 1pm Wednesday, the WRF has rain and thunderstorms moving east of Cincinnati and through the Mid-Atlantic/Carolinas:

The WRF has a large swath of 60mph+ winds just above the ground (in orange and bright red) in the western Ohio Valley by midnight ET:

By 4am, that swath of gusty to damaging winds has pushed east into the Tri-State:

Strong winds may proceed storms late tonight.

Even the latest HRRR model has damaging winds (near the arrow and as thunderstorms come through) in southern Illinois, southwestern Indiana, and western Kentucky by midnight:

While the best tornado threat will be well southwest of the Tri-State early Wednesday, the tornado threat (while it is small) can’t be ruled out. SPC’s version of the WRF model has the best potential for rotating thunderstorm updrafts along the Mississippi River at 1am tonight:

By 6am, the WRF suggest there may be some rotation in thunderstorms moving through the Tri-State:

Summary

Damaging straight-line wind continues to be the main severe weather threat locally early Wednesday. Tornadoes and large hail will secondary threats, with the greatest threat for each staying southwest of the Tri-State. Showers and thunderstorms will be moving through tomorrow morning between 2 and 11am, with the best threat for rain and storms (including strong and/or severe storms) between 5 and 9am.

Please stay safe and weather aware tonight and early Wednesday. Having a NOAA Weather Radio on and programmed correctly could save your life!