Many saw frost in the Tri-State this morning thanks to a clear sky overhead, a calm wind, and a dry air mass in place. The warmest Tri-State locations only dropped into the lower 40s, but most hit the mid and upper 30s to begin Mother’s Day 2013:

Today’s official early morning low temperature of 37° at the Cincinnati/Northern Kentucky International Airport makes Mother’s Day 2013 the 6th coldest start to Mother’s Day on record (the first Mother’s Day was in 1908):

Tonight looks to be colder than this morning with slightly drier air over the Tri-State and winds lighter for a longer period of time.

How unusual is it to see a frost or freeze in May? It’s unusual, but it happens every couple of years. Since 1871, Cincinnati has dropped to or below 32° 24 times, 34° 53 times, 36° 108 times, and 38° 185 times during the month of May (out of a total of 4,242 possible days). The latest spring hard freeze (28° or colder) on record in Cincinnati was in early May, but areas of frost have showed up in Cincinnati as late as May 31st:

Frost can occur at different temperatures; usually, a temperature of 36° or lower with a light wind means frost is a concern.

Nearly all of the temperatures we show you on television are measured about 6 feet above the ground. Because cold air is more dense than warm air (and therefore sinks), the temperature at the ground is often 2-4° colder than 6 feet above the ground. This is big reason why we are encouraging everyone to cover their plants or bring them inside overnight!

It is unusual to drop into the 20s in Cincinnati during the month of May. Since 1871, there have only been 2 hard freezes in Cincinnati between May 1st and May 31st. Here are some additional facts about near freezing temperatures in May:

The weather pattern from early May 2011 is very similar to the pattern we are in now. Note this morning’s low matches the morning low from May 4th, 2011 and tonight’s forecast low temperature matches the low temperature on May 5th, 2011.

I strongly recommend you bring in your plants tonight!

An upper-level area of low pressure continues to spin over the Tennessee Valley at this hour, but it will slowly push east nearing mid-week. This upper-level low can clearly be seen as the swirl in 7:30pm water vapor satellite imagery (sampling moisture 15,000 to 30,000 feet above the ground):

Ahead of this upper-level low is a large plume of low-level moisture, giving most in the Tri-State soaking rain now. Here are some 24-hour rainfall totals (8pm Saturday to 8pm Sunday) in the Tri-State:

The daily rainfall record for Cincinnati today (May 5th) has been already been broken. 1.72″ of rain fell through 8pm today at the Cincinnati/Northern Kentucky International Airport; the old daily precipitation record for this date was 1.67″, set in 1882.

Note many in the far northeastern part of the Tri-State have seen little or no rain, while some southwest of downtown Cincinnati have picked up more than 2″ of rain in the last day.

This morning’s Microcast run does a nice job with the timing of precipitation through Monday night. Microcast suggests light, moderate, and even some pockets of heavy rain will be around at midnight Monday:

Microcast suggests the coverage and intensity of rain will drop some overnight, but there will still be clusters of rain in the Tri-State at 8am Monday:

As temperatures rise through the 50s Monday morning, the coverage of rain will increase. Microcast suggests (and so do I!) you should plan for showers in and around your neighborhood at lunchtime tomorrow:

Microcast still has rain in the Tri-State at 5pm tomorrow, but I don’t expect it to be as widespread in Cincinnati as it was this afternoon:

Rain will be more scattered Monday night and Tuesday as this upper-level low slowly pushes east.

So when will the rain be done for a while? This morning’s GFS model suggests this upper-level area of low pressure (yellow, orange, and red colors) will to our southeast by early Tuesday morning:

Energy rotating around that low pressure center (bright colors) will trigger scattered showers in our area Tuesday. By Thursday morning, the GFS model has this disturbance to our east:

All of the energy with that system will be focused to our east by then, so Wednesday and early Thursday look quiet. The GFS model, however, has more energy (yellow and orange colors) to our west by Friday morning, meaning chances for showers and thunderstorms will return late in the work week:

Wednesday looks to be our only break from this active pattern this week! Longer-range forecast guidance suggests early next week will be quiet but cool.

In the world of meteorology, we spend a lot of time focusing on what is going on near the ground. What goes on above the ground, however, can be just as important if not more important than what is going on near the ground. It is not uncommon for there to be differences in model data near the ground, but upper-level differences are less common. Large upper-level differences often mean big problems when getting a forecast together.

A prime example of how upper-level differences affect the forecast comes later this week and early next week. Meteorologists often look about 18,000 feet above the ground for disturbances and areas of low pressure; later this week, we find little consensus on where a developing area of low pressure will go in the week ahead.

This morning’s GFS model run suggests this developing area of low pressure will be centered over southeast Arkansas Sunday afternoon (Cincinnati is labeled with a dot, and the area of low pressure is in green to our south):

Last night’s GFS model run, however, says that same area of low pressure will be over the Mississippi Valley Sunday afternoon:

Upper-level low uncertainties continue into early next week. This morning’s GFS model suggests this upper-level low will be to our east by next Tuesday evening:

Last night’s GFS model also has this model to our east by next Tuesday evening, but it is much weaker (which could affect rain chances):

Which run of the GFS should a meteorologist believe? Maybe this morning’s ECMWF model will help us decide; it puts the area of low pressure over Iowa Sunday afternoon:

This morning’s ECMWF model has that same upper-level low nearing Toronto by Tuesday evening:

Clearly, there are some large discrepancies regarding where this upper-level wave is headed. For now, we are forecasting little to no rain in the Ohio Valley Tuesday, Wednesday, and Thursday and an increasing chance for rain late Friday through the weekend. At this point, it looks like the best chance for rain and thunderstorms will be Monday, but that is highly uncertain given the forecast path (or lack thereof) of low pressure 18,000 feet above the ground.

Stay tuned for a changing forecast in the week ahead!

Only scattered showers are forecast through mid-evening, but the threat for rain will build later tonight. The threat for thunderstorms is barely there; most will just see rain – heavy at times – after midnight.

Clouds will stay thick through the night. The most recent satellite and radar data snapshot shows scattered showers in our area now, and plenty of rain along a cold front to our west.

This morning’s Microcast run does a nice job with the timing and intensity of rain tonight and tomorrow. Microcast suggests widely scattered showers will be around at 8pm tonight:

By midnight, Microcast keeps the best chance for rain west of Cincinnati:

Microcast (and other models all) suggest there will be plenty of rain around overnight and early tomorrow morning; be prepared for a wet morning commute:

Notice there will be some pockets of moderate to heavy rain early Wednesday morning. Ponding of water on the roads is the main concern for this event. The risk of severe thunderstorms and flooding is low at this point. By 5pm Wednesday, the widespread rain will be long gone and clouds will break some, as Microcast shows:

How much rain will we get? There are some disagreements amongst the latest round of model data on how much rain will accumulating, but most models – including Microcast – suggests most will see 1/4″ to 3/4″ of rain through tomorrow afternoon. Some may see 3/4″ to 1 1/4″ of rain:

Colder air will sweep in behind this cold front. Light winds and temperatures in the mid 30s Thursday morning and Friday morning suggests there may be some areas of frost before the sun comes up.

Today is “Day 1” of a rather active period of weather. While every day this week will not be a washout, there are significant chances for rain each day this week. April is known for showers and thunderstorms, and this week will be no exception.

Satellite and radar imagery reveals thick clouds over the Ohio Valley and showers northwest of Cincinnati as of 4:25pm:

While some in Fayette and Union County may see a quick, passing showers through 8pm, nearly all of the Tri-State will be dry this evening and most of the overnight. By late tonight and early tomorrow, the cold front to our west (the lifting mechanism that helped to produce showers today in the Ohio Valley) will be nearing the Tri-State, allowing for showers and isolated thunderstorms to develop in the Cincinnati early tomorrow morning.

Tuesday will be mostly cloudy with rain and scattered thunderstorms. Given dewpoints in the 60s and temperatures gradually rising through the 60s and 70s tomorrow, strong and severe storms are possible. The Storm Prediction Center has placed most of the Tri-State under a SLIGHT risk for severe storms tomorrow:

Based on the latest model data, large hail and damaging straight-line winds will be the main severe weather threats Tuesday. The tornado threat – for now – is low.

Rain and thunderstorms will be more scattered Wednesday, but ample low-level moisture will support a threat for heavy rain with the strongest showers and thunderstorms. This morning’s WRF models suggests dewpoints will be in the low to mid 60s (yellow and orange colors) Wednesday afternoon:

This morning’s WRF model suggests showers and thunderstorms will affect most of the Ohio Valley, Mississippi Valley, and the Great Lakes by late Wednesday afternoon (largely in part to this surge of low-level moisture):

Thursday will be very similar to Wednesday. This morning’s WRF models suggests dewpoints will be in the low to mid 60s (yellow and orange) Thursday afternoon:

As a result of this low-level moisture, the same WRF model suggest showers and thunderstorms will be widespread to our north and west at 8am Thursday morning; the coverage and intensity of showers and storms will continue building into the afternoon and evening:

In addition to a stalled out front in the area, ample low-level moisture, and warm air in the region, a large upper-level disturbance will approach us Wednesday, Thursday, and early Friday. This morning’s GFS model suggest this disturbance will take on a “bowling ball” shape by Friday morning:

This “bowling ball” shape – especially this time of the year – is usually a catalyst for severe storms if other conditions are present.

The primary focus for strong and severe storms this week will be Thursday night and Friday ahead of this disturbance and with a strong cold front coming through. It is too early to discuss specifics on severe weather threats and timing.

A strong cold front will sweep through the heart of the U.S. and the Ohio Valley tonight, Wednesday, and Thursday. There is still uncertainty about the exact timing and strength of storms in the Tri-State late Wednesday night through Thursday evening, but the threat for severe weather will be higher southwest, west, and south of Cincinnati through Thursday night.

In addition to the cold front, the driving force behind the severe weather threat Thursday will be a large upper-level disturbance moving in from the west. This morning’s GFS model has that upper-level disturbance (in orange and red) to our west early Thursday morning:

This disturbance is a lifting mechanism, so showers and thunderstorms will be likely ahead of it. This morning’s GFS model has this upper-level energy to our north and east by Friday morning, as the cold front pushes east:

The future radar product from this morning’s WRF model suggest showers and thunderstorms will be staying to our north, northwest, and west at 2am Thursday:

By 8am Thursday, the WRF morning suggests showers and thunderstorms will be approaching the Tri-State from the west:

In this particular radar snapshot, more green and yellow colors over orange and red colors suggests showers and storms will arrive in a weakening mode as temperatures drop overnight.

The severe weather threat, however, will continue through Thursday early evening. The cold front will slow down as it moves through the Tri-State Thursday, so strong and severe storms remains a possibility Thursday afternoon and early evening. This morning’s WRF model shows showers and thunderstorms energizing – especially east of Cincinnati – late Thursday afternoon and early evening:

When you break down the severe weather threat by day, the Storm Prediction Center has placed areas northwest of Cincinnati under a SLIGHT risk of severe storms Wednesday night (through 8am Thursday):

SPC has southern, southeastern, and eastern parts of the Tri-State under a SLIGHT risk for severe storms from 8am Thursday through Thursday night:

Damaging straight-line winds and large hail will be the main severe weather threats Wednesday night and Thursday. The tornado threat is in play, but it is the lowest of the main three severe weather threat.

Compared to last winter, this winter has been very cold and very snowy. Compared to average, however, this winter overall was warmer but snowier than average. The lingering cold is getting warm weather lovers antsy for spring and summer.

Most in the Tri-State dropped into the low and mid 20s early Monday morning. The luckier spots only dropped into the upper 20s:

Monday’s early morning low of 22° at the Cincinnati/Northern Kentucky International Airport is a new record low temperature. Another low temperature will likely be broken Tuesday when we drop to 21° (the current record low temperature is 23°, set in 1992).

It is unusual to be this cold in April. 62% of all days so far in 2013 have featured a high temperature below average in Cincinnati. We’ve had over 2′ of snowfall since last summer in the Queen City. With all of this being considered, it could and has been a lot worse.

When you take the high and low temperature each day and average them, you get the “average temperature.” When you take the average temperature for each day so far this year and average them, you get the year-to-date average temperature. When you take this year’s year-to-date average temperature and compare it to other years, 2013 (so far) is only the 47th coldest year (to date) on record:

This graph suggests we have have a lot to be thankful for this year…46 reasons! Those of you know who remember the winters of 1976-1977 and 1977-1978 know true cold.

Part of this year being the 47th coldest year-to-date can be blamed on a colder than average March. In fact, March 2013 was the 13th coldest March on record in Cincinnati (average temperatures in the graph are rounded to the nearest tenth):

14 of 31 days in March 2013 had a high temperature 10° or more below average. Brief spikes in warmth did little to curve the average up.

While below average temperatures have been common since the year began, there have been relatively few brutally cold nights. We’ve only dropped to 7° twice this year in Cincinnati. Our coldest night of the fall, winter, or spring – including i the last several years – is often near or below 0°:

There’s no doubt this year has been colder than average so far. We got spoiled last year with the second warmest March on record, a very mild winter, and very little snow. Spring is a season of transition, and this year’s transition from cold to warm will be gradual and come in spurts. Warmer air is coming later this week, and before we all know it, we’ll be complaining about the heat and humidity.

Meteorological spring began on March 1st, but astronomical spring begins Wednesday morning at 7:02am eastern time. Despite what the calendar shows, it won’t feel like spring tomorrow or any day in the near future.

The colder-than average stretch we’ve been on for a couple of weeks is likely to last at least two weeks more.

NOAA’s Climate Prediction Center issued a forecast Febuary 28th suggesting that there was an equal chance of a warmer or colder than average March. This forecast is unlikely to verify:

The last several days of March will likely be colder than average based on the latest guidance. This morning’s GFS model run suggests temperatures will be well below average (blue and green colors) Thursday morning over much of the nation:

The latest ECMWF ensemble model also suggests below average temperatures (blue and purple colors) for most of the nation early Thursday morning, including in the Tri-State:

If we fast-forward to next Wednesday morning, it’s more of the same. This morning’s GFS model suggest temperatures will be colder than average (blue, green, and purple colors) for the eastern two-thirds of the nation:

The latest ECWMF ensemble model agrees with the GFS model regarding below average temperatures (blue and purple colors) next Wednesday morning:

Based on this model data, it seems unlikely that a significant warm-up anytime in late March. This morning’s GFS, however, suggests a ridge of warmth may be building into the heart of the nation during the last week of March:

This is a promising sign for those of you looking for a warm up. The strength and positioning of this ridge, however, is very uncertain; in turn, there is no guarantee that a warm-up is coming in early April.

In summary, it is too early to speculate on when a warm-up is coming. Confidence is fairly high, however, that the rest of March and at least a few days in early April will be colder than average.

The active weather pattern we have been stuck in for the last several days will not be going away anytime soon. Several disturbances are forecast to move through the Ohio Valley between now and next weekend. Some will be weak, while others will have punch. Some disturbances have little uncertainty surrounding them, while others are very uncertain.

While much of the evening will just be cloudy to mostly cloudy, showers and isolated thunderstorms will develop nearing midnight. A rapidly developing area of low pressure approaching from the west tonight will likely spark clusters of showers and thunderstorms later tonight. This morning’s WRF model has rain and thunderstorms in our area by 2am Saturday:

Given the amount of cold air aloft, small hail and brief gusty winds will be possible with any thunderstorms that form. Confidence is high that showers and thunderstorms will diminish Saturday morning, and much of Saturday will be cloudy to mostly cloudy. Precipitation, however, is likely to return by 8am Sunday morning, as this morning’s WRF model shows:

If you look closely, the model has the 32° isotherm/line in our area when precipitation is falling. With temperatures at and above the ground near freezing early, snow may mix in with rain in the morning. By afternoon, we will have just rain in our area with temperatures approaching 40°. This morning’s WRF model has rain in our area Sunday evening as well:

Greater uncertainty in the forecast comes for Monday as yet another area of low pressure sweeps across the Plains. Given modest instability, there will be a risk for thunderstorms Monday morning, afternoon, and night. There is still some uncertainty on how strong thunderstorms will be Monday and Monday night. The Short Range Ensemble Model suggests the best instability in our area will be in the early afternoon and focused over northern Kentucky:

Given modest instability coupled with the strength and positioning of low-level moisture, upper-level energy, and wind shear, the Storm Prediction Center has placed sections of the Ohio and Tennessee Valley under a risk for severe storms Monday morning, afternoon, and night:

Two weaker disturbance passing through the Tri-State will give us a chance for flurries Tuesday and Wednesday morning.

More energy will move in late next week, bringing rain and perhaps snow showers to the Ohio Valley later next week. The timing and strength of this system is very uncertain.