As we enter the upcoming holiday, you are probably interested in how the weather will affect your outdoor picnics and festivities. Here is a look at what is expected at this point in time:

Friday Forecast: Rain Arrives Throughout The Day 

Rain will likely overspread the region from south to north throughout the day. Areas south of the PA Turnpike could see rain before noon, while locations north of I-80 may not see rain until the evening hours. Expect high temperatures in the 60s for most locations, with 50s anticipated in the higher elevations from eastern West Virginia to southwest/southcentral Pennsylvania.

The image above shows a depiction of the surface reflectivity on Friday afternoon based on 12z Thursday ECMWF model guidance. Image courtesy of Tropical Tidbits. 

Saturday Forecast: Improvement Likely Throughout The Day

Steady rain is expected to come to an end from southwest to northeast throughout the morning and early afternoon hours; however, scattered showers are likely to persist the remainder of the day. At this point it looks as though the heaviest rainfall totals could occur across Ohio and northwest Pennsylvania, but this could certainty change. 

The image above shows a depiction of the surface reflectivity on Saturday afternoon based on 12z Thursday ECMWF model guidance. Image courtesy of Tropical Tidbits. 

Heavy rain could also occur with any thunderstorms that can form in Ohio. Expect high temperatures to range from near 70 in Ohio to the rain-cooled 40s in central Pennsylvania.

Sunday Forecast: A Mainly Dry Day For Some. A Chance of Rain For Others

Sunday will likely feature lower rain chances compared to Saturday. Much of eastern Ohio, Maryland, and western/central Pennsylvania will likely see a mainly dry day with the exception of a few showers. 

The image above shows a depiction of the surface reflectivity on Sunday afternoon based on 12z Thursday ECMWF model guidance. Image courtesy of Tropical Tidbits. 

Areas in West Virginia are more likely to see some showers and possibly a thunderstorm Sunday afternoon/evening. Expect highs to range from the 70s across Ohio, western Pennsylvania, Maryland, and West Virginia to the 60s across most of central Pennsylvania.

Memorial Day Forecast: Mainly Dry For Most. An Isolated Shower or Storm Possible

Memorial Day: Monday appears to be a mainly dry day for many locations in our region. A pop-up shower or storm may occur in a few locations, but most locations should see mainly dry conditions throughout the day. At this point, it appears that southern areas would have the best chance of seeing wet weather. Expect high temperatures in the 70s in most areas.

The image shown above shows a depiction of the surface reflectivity on Monday afternoon based on 12z Thursday ECMWF model guidance. Image courtesy of Tropical Tidbits. 

Expected Rainfall Totals Through Memorial Day

While all areas of our region will see rainfall through Memorial Day, some locations will likely see more than others. The determining factor for which regions see the highest rainfall totals will be the location of a high pressure system over New England and a surface area of low pressure tracking through the Ohio Valley. 

The image above shows a depiction of expected total precipitation through late Monday night based on 12z Thursday ECMWF guidance. Image courtesy of Tropical Tidbits. 

At this point, it appears that Ohio, West Virginia, Maryland, and southcentral Pennsylvania may see the highest amounts with totals of 1.5 to 2.5 inches, while western and northern Pennsylvania may see totals closer to the 1-1.5 inch range. 

While this summary gives a general idea of what is currently expected, keep in mind that this forecast will likely change over the next couple of days.

Refer to the following resources for additional information:

• National Weather Service
• WPC Winter Weather Forecasts
• NWS Cleveland
• NWS Pittsburgh
• NWS Buffalo
• NWS State College
• NWS Charleston
• NWS Binghamton
• NWS Baltimore/Washington
• Weather Prediction Center
• Pivotal Weather 
• Tropical Tidbits

Our active start to severe weather season is likely to continue later this week as a shortwave and associated cold front dive southeast toward the Ohio Valley on Thursday. At this time, it appears that damaging winds and large/very large hail would be the primary threat, but isolated tornadoes may also be possible. Considering the moist low level flow and parallel boundary storm motion, flash flooding may also be a concern. 

Some of the key highlights that we will cover in this blog include: 

• Meteorological Setup for severe weather
• Expected storm mode and severe weather hazards
• Timing and Areas of greatest risk 

While forecasting severe weather days in advance can be challenging, this blog will discuss some possible outcomes. 

Meteorological Setup For Severe Weather 

An unusually strong early spring ridge of high pressure will continue to bring very warm weather to the central Plains over the next several days. At the same time a shortwave diving southeastward from the Northern Plains will push a cold front toward the Ohio Valley and Central Appalachian region on Thursday. An area of high pressure that is currently situated over the eastern United States will move off the eastern seaboard as we head toward mid-week. Clockwise motion around the retreating high pressure system will help to return Gulf moisture into the region ahead of the approaching cold front. This will set the stage for the potential severe weather episode across our region. 

The image above shows the 500 mb pattern on Thursday based on 18z Tuesday GFS model guidance. Image courtesy of Tropical Tidbits. 

Ahead of this system, a moist flow will develop, helping to provide the surface moisture needed for severe weather. In addition to the sufficient low level moisture, it is also likely that there will be strong speed shear present. If lapse rates become steep enough to overcome a capping inversion, there is the potential for supercell storms to produce large/very large hail and damaging winds. While the potential is relatively low at this time, it is possible that there could be a couple of tornadoes if there is enough low level moisture and low level directional wind shear available. At this time, it appears that eastern Ohio may be the most favored area for severe weather in our area, but all locations should be prepared for the potential of severe weather late Thursday into Thursday night. 

Expected Storm Mode And Severe Weather Hazards

Due to the steep lapse rates aloft and somewhat limited surface-based instability, it is likely that an elevated storm mode will be most dominant. With that being said, it is possible the low level moisture, combined with lower lifted condensational level (LCLs), will be sufficient to support a few surface-based supercells with a tornado potential. Otherwise, adequate speed shear aloft will likely lead to elevated supercells capable of producing downburst winds and large hail. It is possible that very large hail may occur if instability is high enough to support strong updrafts.

The image above shows a depiction of the 2-5 km updraft helicity for Thursday’s event based on 12z Tuesday NSSL MPAS-RN model guidance. Image courtesy of Pivotal Weather. 

If surface winds are too parallel to the boundary, it is possible that the storms may quickly form into a convective line. In addition to the severe weather potential parallel boundary winds may lead to storms training over the same areas multiple times. Given the expectation for elevated dewpoints, it is possible that some instances of flash flooding may occur, especially in areas that experienced heavy rainfall on Sunday. 

Timing And Areas of Greatest Risk 

At this point in time, model guidance would suggest that Ohio may have the greatest risk for severe weather due to better moisture and more optimal timing of the storms. With this in mind, sufficient ingredients for severe weather may be in place across the entire region and future model guidance should be monitored for potential eastward shifts in the risk area. 

The image above shows a depiction of the surface reflectivity on Thursday evening based on 12z Tuesday NSSL MPAS-RN model guidance. Image courtesy of Pivotal Weather. 

The most likely timeframe for severe weather will depend on a couple of factors. The first factor will be dependent on prefrontal supercell initiation and the other will be the eventual speed and progression of the system. While it is too early to forecast the exact timing of storm arrival, it currently appears that storms would arrive across northern Ohio during the late afternoon/evening and progress southeastward toward the rest of the region through the rest of the evening/early overnight hours. As would be expected, a later arrival of the system would likely somewhat decrease the risk of severe weather in our area. 

As always, the details regarding the potential for severe weather timing, location, and impacts will become more clear as the event approaches and CAM’s can better sample the atmospheric ingredients.

A powerful early spring low pressure system will develop in the Plains and strengthen as it moves into the Great Lakes on Monday.

Due to the rapidly strengthening storm and its neutral/negatively tilted trough, there will likely be very strong wind shear ahead of the cold front. While moisture return in the warm sector may be limited, it is possible that the strong kinematics may be sufficient to produce severe weather across parts of the region Monday afternoon.

Some topics that we will discuss in this blog include: 

• Meteorological Analysis of The Storm System
• Potential Impacts From The Storm Across Our Area
• Timing of the Front Is Important

Now let’s dive into our discussion about the upcoming powerful storm system!

Meteorological Analysis of The Storm System

As we head into Sunday, a strong storm system will begin to develop across the central United States. As the storm begins to move northeast toward the Great Lakes, it is expected to intensify into a strong mid-latitude cyclone by Monday. The storm system will also begin to transition from a neutral to a negatively 500mb trough as this process occurs. 

The image above shows a depiction of the 850 mb jet winds across the area early Monday afternoon based on 18z NAM 12 km  model guidance. Image courtesy of Pivotal Weather. 

This will result in a strong low level 850 mb jet streak that will develop across the Mississippi Valley on Sunday and move across the Ohio Valley, Mid-Atlantic and Northeast on Monday, leading to impactful and potentially damaging weather conditions across a wide swath of the central and eastern United States. 

Potential Impacts From The Storm Across Our Area

Due to the rapidly strengthening storm and its neutral/negatively tilted trough, there will likely be very strong wind shear ahead of the cold front. While moisture return in the warm sector may be limited, it is possible that the strong kinematics may be sufficient to produce severe weather across parts of the region Monday afternoon.

The image above shows a depiction of the Energy Helicity Index (EHI) across the region early Monday afternoon based on 18z NAM 12km guidance. Image courtesy of Pivotal Weather. 

While it is too early to analyze many of the convective allowing, high revolution model guidance, the pattern appears favorable for the potential for impactful damaging winds and potentially embedded tornadoes along the cold front. When analyzing the 18z NAM 12 km guidance, we can see that there is a decent Energy Helicity Index (EHI) across our region Monday afternoon. This parameter helps to determine where the best overlap of instability and wind shear are located. The severe weather potential will likely be most prevalent in the area where the EHI is at its maximum. If sufficient moisture returns ahead of the front occurs, it is possible that a few discrete supercellular storms could develop as well. At this time, this idea appears unlikely across most of our area. 

Timing of The Front Is Important 

The timing of the front will be important. If the system is slower to arrive, the potential for severe weather would increase across many areas. A frontal passage that occurs during the morning hours would not allow for much surface heating and destabilization to occur prior to the passage of the cold front; whereas, an afternoon frontal passage would allow for a heightened severe weather potential, resulting from stronger updrafts. Even if the timing of the front is not favorable for severe weather, it is possible that a line of strong to damaging winds will still occur, given the strong low level jet that will be moving through the region.

It is important to emphasize that the potential impacts from this storm system are still two to three days away, and changes to the forecast will certainly occur over the next couple of days. 

As we approach the end of winter, many people are looking forward to the return of warmer weather in the coming weeks. While the approach of spring is a welcoming thought following a cold winter, spring time can also bring with it the potential for severe weather episodes that deliver damaging winds, large hail, and tornadoes. While severe weather is complicated, there are four primary ingredients that are necessary for the development of severe weather.

These ingredients include: 

• Shear: Wind shear measures the amount of change in wind speed and direction through the atmosphere. 
• Lift: The amount of positive buoyancy (or upward motion) available for air parcels to rise and form clouds and precipitation. 
• Instability: Instability or convective available potential energy (CAPE) refers to the amount of energy that is available for the atmosphere to produce thunderstorms. 
• Moisture: Warm, moist air rises to the lifting condensation level (LCL) where condensation occurs. Strong upward motion can then lead to tall convective thunderstorms that can produce severe weather. 

The image above shows a depiction of the precipitation pattern for the spring based on the NNME model guidance. Image courtesy of Tropical Tidbits. 

The availability of these ingredients will largely depend on the jet stream pattern that develops across the United States as we approach spring. If the jet stream sets up in a wavy pattern, the number of severe weather opportunities will likely increase as systems bring in the warm, moist air and wind shear needed for severe weather development. 

How Does ENSO Affect Severe Weather?

The persistence of an active severe weather pattern into late spring and early summer will likely depend on how quickly El Nino develops in the equatorial Pacific Ocean. A quicker transition to El Nino would favor a decrease in severe weather, while a continuation of El Nino Southern Oscillation (ENSO) neutral conditions could lead to severe weather continuing into the summer. 

The images above show a depiction of tornado and hail frequency associated with positive and negative ENSO conditions. Image courtesy of National Oceanic and Atmospheric Administration (NOAA).

Through much of the winter season, La Nina conditions have been observed in the equatorial Pacific. With that in mind, La Nina has begun to weaken in recent weeks and is likely to progress to neutral condition this Spring. An eventual transition to EL Nino appears likely during the summer or fall season of 2026.

The image above shows the ENSO forecast based on guidance from various long range forecast models. Image courtesy of the National Weather Service.

The Big Picture

While uncertainties exist in any long range forecast, the general consensus favors a fairly active severe weather season with near to above average severe weather observation expected in the area. Now is the time to start thinking about severe weather safety so that you are prepared to protect your family and property during severe weather. 

It is important to note that uncertainties still remain in the frequency and intensity of severe weather during the upcoming spring, and this blog may be updated in the future to account for changes to the forecast.