Public Analysis: Another Week of Extremes on Tap

If you enjoyed the record warm temperatures, severe weather, and sudden return to more winter-like conditions that we experienced over the past week, then you’re in luck! This week is shaping up to be very similar to last, with record or near-record temperatures possible in the middle of the week, followed by a strong cold front passage that will leave the entire area right around seasonable or just slightly below average for this time of year with a possible clipper system passing near the area by the end of the work week.

This afternoon was rather pleasant with some mid to high level clouds noted on visible satellite imagery as a high pressure system located off of the mid-Atlantic coast remains in control of our weather for the rest of the day and into tomorrow. As we progress into late afternoon hours and evening, cloud cover will begin to increase over the entire area as southerly winds usher in a moist airmass in the low levels of the atmosphere. Since the cloud cover will be relatively heavy, temperatures will have a hard time dropping much this evening, so expect temperatures to only be in the mid to high 30’s inland and in the lower 40’s for the coastal regions as well as southern locations. Some patchy drizzle may be possible as the low level moisture mentioned earlier begins to increase as we head into the evening hours.

Current visible satellite and surface observations showing a rather thick cloud deck overspreading the Northeast (Simuawips.com)

Current visible satellite and surface observations showing a rather thick cloud deck overspreading the Northeast (Simuawips.com)

As we move into Tuesday, a warm front should gradually begin to overspread the region in the morning and bring a cloudy start to the day. As we progress into the afternoon hours, temperatures should rise into the upper 50’s to mid 60’s areawide, with cooler temperatures around the mid 50’s likely along coastal locations. High level clouds may allow some sunshine to break through tomorrow afternoon, but as another warm front moves through in conjunction with some upper level energy from a disturbance passing near our area, low clouds and even some rain are quite possible by the afternoon. Low level clouds should continue to increase into the evening hours, with some steadier rain showers possible by late evening. Though winds look to be a little too strong for fog in the evening, warm winds coming off of the ocean and low level moisture in place may allow for at least the coastal communities to see some periods of fog, though this will have to be looked at in greater detail as we get closer to tomorrow evening.

NAM model showing winds coming off of the Atlantic on Tuesday afternoon, providing cloudy conditions as well as a threat for showers later in the day

NAM model showing winds coming off of the Atlantic on Tuesday afternoon, providing cloudy conditions as well as a threat for showers later in the day into the evening hours

Wednesday should be the most eventful day of the week in terms of sensible weather as the warm front that initially approaches the region tomorrow begins to advance north. The initial fog and rain showers should diminish by late morning, giving way to at least some sun breaking through the clouds. Temperatures should quickly rise deep into the 60’s and even low to mid 70’s by the afternoon hours, which could break numerous records once again across our area. Since we still do hold on to southerly winds, coastal sections as well as Long Isalnd may be limited as to just how warm they get.

As a strong cold front associated with a low pressure system moves through the Great Lakes Wednesday afternoon, winds from the south will usher in a very moist airmass for this time of year which will allow the atmosphere to become quite unstable. Even before the cold front and its associated “lift” which helps to build thunderstorms arrives, some showers and thunderstorms will be possible by the early afternoon hours. These shower and possible thunderstorms will mainly be limited to heavy rain and perhaps some gusty winds, but after these initial storms pass through is when the main event of the day looks to unfold. As we begin to destabilize the atmosphere again later in the afternoon, very strong upper level wind shear as well as significant lift will be present over the metro area, which will be quite favorable for organized severe thunderstorm development capable of potentially damaging winds. Though model guidance is beginning to key in on the potential for severe thunderstorms to pass near or over the area later in the day and into the evening, there are still some very important details that will have to be worked out during the day on Wednesday. One of the key factors to this potential severe weather threat will be just how widespread the initial showers and thunderstorm development is Wednesday morning, which will ultimately determine where the best instability is located, as well as where the leftover low level boundaries are located (which could locally enhance storm development). As of this morning, the Storm Prediction Center in Norman Oklahoma has placed our area in a Slight Risk for severe thunderstorms on Wednesday with damaging wind gusts being the most likely risk at this time. Make sure to stay tuned as we will have continuing coverage of this potential severe threat over the next 48 hours.

Afternoon NAM model showing strong thunderstorms approaching the tr-state area by late afternoon

Afternoon NAM model showing strong thunderstorms approaching the tr-state area by late afternoon

Behind the front will come a dramatically changed weather pattern. Thousands of miles to our north, a blocking ridge near Greenland will begin to have its effects on the weather throughout the hemisphere. Northern jet stream disturbances will slide southward through the Great Lakes and into New England, with colder air lingering across the Northeast parts of the United States. The first of these disturbances comes late this week in the form of a transient clipper system. Forecast models have wavered with the storms exact track, but a weak low pressure area tracking quickly through the Northeast US on Friday holds the potential to deliver some light snow — especially in New England. The exact track of the low pressure area will determine where the swath of light wintry precipitation falls. Make sure to stay updated with the active weather week ahead! For more information and posts like this one, make sure you sign up for Zone Forecasts — where multiple detailed articles, videos, and interactives are posted each day.

 

Have a great evening!

Enhanced Risk for Severe Weather in the Ohio Valley on Friday

3:30pm Update: So far, everything is on track with respect to downplaying the event relative to SPCs and other outlooks’ expectations. As expected, there is still a lingering strong capping inversion in the warm sector, so there is not enough lift to generate strong thunderstorms to take advantage of the instability. Additionally, the low-level jet (LLJ) still continues to lag significantly behind the daytime heating, so the low-level winds are not strong enough for additional lift, superceullar organization, nor for transporting severe wind gusts down to the surface. There are only a few isolated wind reports so far, which is far below the threshold for an “enhanced” risk.

Current SIMUAWIPS analysis shows plenty of convective inhibition (CINH), preventing storms from taking full advantage of daytime heating.

Current SIMUAWIPS analysis shows plenty of convective inhibition (CINH), preventing storms from taking full advantage of daytime heating.

We still do think that later this evening, when the storm system strengthens a bit and frontal forcing increases, we’ll get a decent low-level jet increase late this afternoon and through this evening, which may produce a strong to marginally severe line of storms along the cold front from eastern Indiana into Ohio. We still think Ohio may be more likely to see strong to severe winds since they are in the best location for an increase in the low-level jet. Some initially isolated discrete cells out ahead of the line may be able to produce some hail in Indiana and perhaps parts of Ohio, but the linear wind profiles indicate a transition to a line with moist mid-levels, so we do not expect many severe hail reports.

Additionally, the low-level jet is way too linear and weak right now to generate the necessary updraft helicity for tornadoes — which is why we never bought into a true tornado threat. There still may be some isolated tornado reports later this evening if some discrete cells can form ahead of the line of thunderstorms when the low-level jet does increase in strength. Fortunately, any tornado threat will be isolated and any tornado that does form should be weak.

Previous Content: During this early-spring…I mean late-winter day, the ingredients are beginning to come together for an impressive severe weather episode on Friday in the Ohio Valley. A strengthening storm system which will provide blizzard conditions for parts of the Northern Plains will have its warm sector line up perfectly with Gulf of Mexico moisture transport and instability. Furthermore, this strong storm system will be dragging a strong cold front to its east, helping to increase low-level moisture return via strong low-level winds from the Gulf of Mexico, provide plenty of lift via the frontal forcing, and also provide very cold mid-level temperatures. This is because behind the cold front, mid-level temperatures are very cold since there is actual winter-cold behind the front, but mid-level winds often blow so fast that they advect the mid-level cold air to places on the warm side/ahead of the cold front, helping to juxtapose a warm, moist airmass with cold air aloft and a lifting mechanism — perfect ingredients for thunderstorm formation. This cold air aloft and thus very strong thermodynamic and dynamic lifting with these types of systems this time of year often make up for not having a true summer-like low-level airmass and can provide lift equal to that of spring and summer-like outbreaks.

From here, the devil lies within the details as far as taking this severe weather episode from minor to major. At this point, we think this event will be somewhere in between. While the above details portend a significant outbreak, there are more nuances to this event, such as jet-streak behavior, as an alignment of strong jet streaks can turn lift from merely sufficient for thunderstorms, to majorly supportive. And what we see currently is a not ideal alignment of jet streaks in the low-levels and the upper-levels with when the storms actually initiate.

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Monday Overview: Oppressive Heat with Severe Thunderstorms Possible Today

The fourth day of a heatwave — and likely the peak of it — is underway throughout the area. A stronger mid-level ridge and a deeper southwesterly flow will cause temperatures to reach the middle to upper 90s this afternoon. Some spots could reach 100F with enough sunshine. The big difference compared to the past few days, however, is that more humidity will cause oppressive heat today. Heat index values could be between 105° to 110° F this afternoon.

As a pre-frontal trough and then cold front approaches, some showers and thunderstorms are likely in the area from late this afternoon through the evening. There is some potential, with increasing instability and shear, for some more organized strong to severe thunderstorms. Damaging wind gusts will be the main threat from these thunderstorms. The Storm Prediction Center now has a slight risk for severe thunderstorms for most of the region this afternoon and evening. Thunderstorms could also produce frequent cloud to ground lightning and very heavy rainfall with localized flash flooding. Some other highlight for next few days:

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Unsettled Weather Today…Stormy Sunday Possible

More unsettled weather is likely today. A couple of upper-level disturbances embedded a inside larger trough, will be moving through region today. Skies will remain mostly cloudy with some scattered showers. A few isolated thunderstorms with heavy rainfall are also possible, especially northwest of New York City. Closer to the coast, a more stable marine influence from onshore flow will cause any convection to weaken. A cold front is expected to move through the region early tonight, with more showers and few isolated thunderstorms possible again. Temperatures tonight will drop into the middle to upper 60s.

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