May Snow & Cold in Cleveland/Northern US

Here in northern Ohio we typically say that if you make it to Tax Day, the chances of seeing snow are pretty remote. Not this year. Late April cold invaded the eastern half of the US and again in early May!  A ton to unpack here so let's get to it.

~2" snow in Auburn Township - May 9, 2020

The month didn't start off super-cold. We had a few days in the 70s during the first weekend. Watch the progression of the cold across the northern US via the RTMA temperatures between May 2nd and 5th.

Historically this is what May should look like.

There have 19 years since 1950 with at minimum snow flurries in May and only a handful of years with measurable snow. I remember May 15, 2016 because I was at a baseball tournament coaching. It was a Sunday and there was snow on the ground at 7am!

Earlier last week, the models were showing a strong surge of cold for Friday/Saturday, May 8-9th. Based upon both the GFS and EURO long range data for Detroit and Pittsburgh--IF verified--this would tie or possibly break the all-time upper level sounding data record for 850mB (5000 feet) cold !set back in 1966 While this isn't where we work and live, this level is critical for determine lake effect snow and surface temperatures.

The sounding history for Detroit shows the EURO forecast for both temperature and 500mB heights at record levels for early May

This is what the 850 mB temperatures read at 8am Saturday morning, May 9th:

Temperatures at 500mB (18,000 feet) were also extremely cold for early May.

Our forecast called for "thundersnow" due to the large temperature change from Lake Erie (45 degrees or 7.5°C) to the temps above (-32°C)

Radar loop Saturday morning showed definitive areas of lake effect

North Royalton

Highest amount: Auburn Township - ~2"

Northern Ohio snow reports - courtesy NWS Cleveland

Northeast snow Saturday May 9, 2020

Check out the progression of record lows Saturday morning across the US.

Core of the cold over the Ohio Valley, Great Lakes and New England Saturday morning.

Wind chill at NWS Cleveland dropped to 20 at 7:51am Saturday May 9th

Has this happened before?  Here are two composite years:  1986 and 1966

After a break Sunday with temperatures near 60 with storms/shelf cloud passage in the early evening...

Vermilion - May 10, 2020

...another clipper front passed through early Monday morning, May 11th. Yet another shot of frontal/lake effect snow!

Chardon - ~2" of snow - May 11, 2020

Hambden Township - May 11, 2020

Mayfield Heights - May 11, 2020

* 2020 marks the only year in Cleveland (NWS Cleveland-Hopkins) since 1954 with multiple days of snow flurries and/or measurable snowfall in the month of May

* New record snowfall this late in the season at NWS Cleveland: 0.2" on May 11th which breaks old record on 5/10/1907

* 5/11/2020 high of 45 was also the COLDEST high temperature in the last 100 years this late in the season (tied 5/11/1996)

We still haven't reach 80 degrees this year. A warm up is coming! (regression to the average which is now nearing 70)

Potential high temperatures Thursday, May 14th

Here are the years when we touched 80 or better after May 15th (since the 1930s). The list is short:

Lake Erie Sunset 5/11/2020

Progression of April Cold

After an extremely mild winter, the pattern across the North American continent shifted significantly colder around the second week of April. 

Remember that April started off above normal across the eastern US. The first 9 days of April the average high temperaure was close to 60 degrees in northern Ohio! We reached 72 on April 7th.  Slowly colder air settled in especially across a large portion of the country. Each graphic below illustrates the gradual progression of the cold (above/below normal temperatures) in 20,15,10,7,5,3,1 day periods prior to April 15th. The last graphic is the 5 day period from April 15-20th.

20 day temperature anomalies - 20 days leading up to April 15

15 day temperature anomalies - 20 days leading up to April 15

10 day temperature anomalies - 20 days leading up to April 15

7 day temperature anomalies - 20 days leading up to April 15th

5 day temperature anomalies - 20 days leading up to April 15th

3 day temperature anomalies - 20 days leading up to April 15th

1 day temperature anomalies - 20 days leading up to April 15th

5 day temperature anomalies - 20 days leading up to April 20th

Why these early spring changes? Let's go back to the winter for a moment. The pattern was dominantly mild. There was no "blocking" over Greenland.  The Arctic Oscillation stayed STRONGLY positive. The Polar Vortex was strong with no big perturbations south. 

The next three slides are the 500mB heights for each month January through March 26th.  High pressure over the northern Pacific. SE ridge across the US. Low pressure over the poles/North Atlantic.

By the last week of March, notice the changes. The northern Pacific high shifted west. A strong ridge developed in the North Atlantic! The SE ridge from March was still intact.

These pressure changes were a significant sign that April would more than likely feature some significant changes in areas that were used to above normal temperatures especially the eastern US and possibly the Great Lakes. (April 5th I posted a tweet noting that the next 10-14 days would feature some cold air/below normal temperatures) 

By the first week of April, the ridge across the eastern US was breaking down. High latitude blocking was present.

Between April 6 and 10, the high started to pop back in the southern states. Northern Pacific ridge was far weaker. The trough in New England was building in response to the blocking

By April 11-15th the trough/ride wavelength were much larger. The central US/eastern US trough had grown (blue colors) and was locked in.

April 16-19th featured the dominant trough across much of the US and Canada with the exception of Florida.

Watch how the colder air bled southeast throughout early/mid April in response to the upper level changes. From April 14 to the 23nd we had 5 days in the 30s and 40s with wind chills in the 20s in spots!

Is this "cold mid-April" unprecedented?  Here are some years in the past with cold mid Aprils similar to 2020. (Temperature anomalies from April 12-21 for the years 1875, 1943, 1953, 1983, 1997 and 2007 pictured below. I am sure I missed a few)

How about here in northern Ohio. Where does this cold mid April rank?  Here is the list: 2020 rank 33rd.  Also keep in mind that 32 of the 40 years listed occurred BEFORE 1960. The last year similar to this year was 2018 then 2007, 1975.

Here's a more recent analysis: Below is a graph showing the number of days with below normal temperatures through April 2nd since 1990 (last 30 years) in northern Ohio (Hopkins Airport-Cleveland). Perhaps we forgot about 2018 with MORE days below normal than 2020.

How about April snow in these years?  Great question.

This year we've had 9 day with at least a trace of snow (through April 22). Two years ago (2018) we had.....13!

So while it has been colder than normal in April, it is not unprecedented.  The recency effect is strong here as we may have placed more weight on this year because it is front of mind.

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A FEW THINGS TO NOTE:  THE COLD APRIL ISN'T A RESULT OF THE RELATIVELY MILD WINTER. SIMPLY BECAUSE THE WINTER WAS "MILD" DOESN'T AUTOMATICALLY MEAN APRIL WAS GOING TO BE COLDER THAN NORMAL. ALSO, THE GLOBAL/CONTINENTAL DRIVERS OF WEATHER PATTERNS IN WINTER CAN PRODUCE DIFFERENT TEMPERATURES, ETC IN SPRING AND SUMMER. THIS IS NOT CONFIRMATION OF "GLOBAL COOLING". IN FACT ONLY A SMALL PERCENTAGE OF THE WORLD HAS HAD TEMPERATURES BELOW NORMAL THIS MONTH.

Will Opening Day 2020 at Progressive Field be "COOLER THAN NORMAL"?

If you recall from my blog a few weeks ago when I dove deep into why the winter pattern was abnormally warm, one of the drivers was the lack of ridging over Alaska.

Early January Pressure Pattern

Now, the models are strongly showing a monster ridge late this week/weekend.

Recall what happened back in November when the ridge was locked in. Plenty of cold across the eastern US.

The ridge looks incredibly strong for this time of year.

Based on the strength of this huge Alaska ridge and comparing this to the top 5 years similar (hat tip: Brian Brettschneider) the surface temperature departures for +2 days later through +14 days later look colder than normal the last full week of March for the Ohio Valley and northern states! (March 16 thru 28th).

The EPO is strongly negative

The MJO is also heading into a cooler phase.

The MJO isn't as strong as what it was earlier in the winter so IMO this won't be as much of a driver if it stays weak.

CIPS analog (based on the GFS) is still warm east between March 21 and 24. This should start to correct COLDER east in the days ahead.

Good possibility that temperatures could be COOLER THAN NORMAL for Opening Day here in Cleveland. Normal high for March 26 is 51°. We could end up with mid/upper 40s more days than not that week!

March Outlook Analysis

Checking the SOI late last week (February 28th) showed a sharp 25 point rise between February 19-21st. The SOI composites for both a neutral winter and an El Nino winter show weak central US pressure centers. No significant large scale blocks or deep troughs over the next 15-18 days from the composite starting point of February 20th. This should translate to a overall west-to-east movement on storm systems. Most of these will be rain producers for the Ohio Valley.  Any changeover to snow would be brief. These maps are for ~ March 7-10th

FIGURE A

The MJO is now in the inner circle. A far cry from the higher magnitude MJO from earlier in the winter especially January. The overall monthly temperature composites show a more transient temperature setup across the central US/Ohio Valley through the middle of March

FIGURE B

FIGURE C

EPO (Eastern Pacific Oscillation) teleconnection last Friday showed two dips into negative territory.  One around the 7-9th and another less confident dip at mid-month. The first dip coincides with the SOI composites from above.

FIGURE D

Today (5 days later) the EURO and GFS ensembles have backed off on the second dip (mid-month). The EURO is more bullish on a colder pattern than the GFS.

FIGURE E

The EURO ensembles from last Friday (February 29th) showing the pressure pattern through March 14th. Cold colors represent low pressure.  Warmer colors represent higher pressure. Lines indicate west-to-east winds aloft between March 10 and 14th...This represent fast moving storm systems. See the SOI composites above.

FIGURE F

Remember how the today's model EPO output (FIGURE E) for March 18-19 was all over the place? EURO more positive/GFS more negative?  Today's EURO ensemble (Wednesday March 4th) mirrors the west-to-east pattern from last Friday overall. Notice the "buckle" in the central US flow between march 12-14th? That subtle element (also on the GFS--not shown here) is something to watch over the next 4-7 days.

Also Remember the "???" on Figure A above?  The SOI is now showing a sharp 32 point drop

Looking at the SOI composites (17-20 days out from the starting point of Feb 27-29 which puts us at roughly March 17-20th) the answer gets even more murky. The composites couldn't be more opposite. One shows a strong SE ridge/active central storm systems.  The other shows the SE ridge more suppressed with a more active panhandle storm track. 

REMEMBER THIS BIG SOI DROP.  THIS BARES WATCHING.  STAY TUNED!

The northern Pacific pattern has been progressive. No sustainable ridging over the Bering Sea or over Alaska. Fast flow aloft is keeping LOWS barreling east from out of central Asia, over the Pacific and into western North America.

Based on all of this we can conclude the following for the first 3 weeks of March:

* Temperatures should stay near/slightly above normal
* More days in the 50s overall
* Rapid west-to-east flow will keep storm systems moving frequently across the central US 
* Small periods of colder air still possible. Light snow is not off the table.
* Watching the period of March 17-20th