An active weather pattern brings yet another week of cool, rainy weather. Tuesday will be the only day with sunny skies and near normal temperatures with high pressure briefly building in. Otherwise, a couple slow moving storms will bring clouds and rain the rest of the week. This will result in temperatures largely running below seasonal averages. I suppose that’s some incentive for people to stay safe and quarantine at home?
Rest of today – early rain chances should diminish steadily. High temperatures cool, only around 50ºF under the influence of northerly flow as the slow moving coastal storm that impacted us yesterday and today moves off to the northeast. Clouds should start to diminish later in the day. Overnight lows in the low-40s.
NAM output forecast cloud cover for 11AM Tuesday
Tuesday – we should see a brief window of sunny skies and dry weather as high pressure builds and passes over for the day. This break in rainy weather should allow temperatures to climb into the low-60s. Overnight lows in the mid-40s.
Wednesday – the reprieve from dreary conditions barely lasts a day as yet another storm system takes aim at the area. With the high pressure Tuesday slow to move east, this next storm will be similarly as slow moving as this past weekend’s storm. The result for Wednesday, even if we don’t get too much in the way of rain, will be cloudy conditions and cool, southeasterly onshore flow ahead of an advancing warm front. This will cause temperatures to cool into the mid-50s. Overnight lows barely budge, and hover around 50ºF.
Weather Prediction Center surface forecast for 8AM Thursday
Thursday– the second storm of the week hits with steady rain and southeasterly onshore breezes. Warm advection could help temperatures stay slightly above 60ºF, with overnight lows in the low-50s.
Two coastal lows bring will rain today and Sunday. Saturday ends up being a nice day in between with some high pressure building briefly. The second coastal storm coming on Sunday drags into Monday bringing rain and cool temperatures. Throughout this period, temperatures will range at least 5ºF below normal. This below normal temperature trend, largely a continuation of this week, looks set to continue well into next week.
Rest of today – high temperatures in the low-50s with cloudy conditions and periods of steady rain off and on for much of the day. Overnight lows in the low-40s with rain winding down and clouds clearing.
Saturday – sunny skies and high pressure should allow temperatures to climb to about 60ºF. Overnight lows in the mid-40s.
Weather Prediction Center surface forecast for 8AM Sunday
Sunday – unfortunately, the dry weather doesn’t last as a second storm moves in for Sunday, bringing yet more rain and cool, cloudy weather. High temperatures topping out only in the low-50s. Overnight lows in the low-40s.
Monday– high temperatures still suppressed in the low-50s as this second storm lifts to the east. Overnight lows in the low-40s. Going into next week, temperature will stay below normal, anywhere between 5-10ºF. Later in the week, it appears a potent, closed 500 mb low will be the culprit for keeping temperatures down (and bringing yet more rain to us)
Climate Prediction Center temperature outlook for Apr 29-May 3, showing below average temperatures continuing to affect much of the northeastern quadrant of the US
GFS 500 mb temperature, height and winds for 2AM Thursday, Apr 30. A closed 500 mb low is forecast to move over the Great Lakes and southern Ontario – this will be partly responsible for cooler than normal temperatures.
A couple storm systems will impact NYC this week. The first of these could bring some thunderstorms and gusty conditions tomorrow afternoon. Later this week on Thursday, a second storm bringing steadier rain will move through. Temperatures throughout this period will be generally 5ºF below normal. Tuesday and Wednesday overnight lows could bottom out in the upper-30s.
Rest of today – mostly cloudy, with clouds diminishing later, high temperatures in the upper-50s. Overnight lows in the mid-40s.
Weather Prediction Center surface forecast for 8AM Tuesday
Tuesday – quick moving storm will push a warm front and then a strong cold front through Tuesday afternoon. Showers should begin in the afternoon and a line of thunderstorms is possible with the cold front. High temperatures around 60ºF with southwesterly flow ahead of the cold front. Overnight lows in the mid-30s.
Wednesday – the low bringing the rain and thunderstorms on Tuesday continues to strengthen. The pressure gradient will tighten around this low and bring windy conditions but with sunny skies. High temperatures cool off into the low-50s. Overnight lows in the upper-30s.
GFS 2-meter above ground level temperature anomalies for 2AM Thursday. A cold night in store for many parts of the Northeast!
Thursday– partly sunny skies with high temperatures climbing into the upper-50s. Overnight lows around 50ºF with rain developing.
An extended period of cool temperatures continues for the rest of the week into the weekend. During this period, highs will generally 10ºF below average. A weak storm passes through Friday night into Saturday bringing the chance for rain. Temperatures finally warm up to start next week though this may not last.
Rest of today – mostly sunny with high pressure building. High temperatures in the low-50s. Cold overnight lows in the mid-30s with a cool air mass in place. If skies remain clear and winds decouple overnight, we could see even colder overnight temperatures.
Weather Prediction Center surface forecast for 2AM Friday
Friday – with a cold start to the day, high temperatures will be hindered around 50ºF. Clouds increase as a low pressure center moves towards us. Rain chances increase later in the day and into the overnight. Overnight lows around 40ºF
Saturday – rain ending early, as the storm system slides east of us. High temperatures hampered by this early rain and clouds, reaching into the mid-50s. Overnight lows around 40ºF.
Climate Prediction Center temperature outlook for April 21-25, showing chances for below normal temperatures in the Northeast
Sunday– high temperatures start warming up to around 60ºF. Overnight lows will likewise warm into the upper-40s.
A powerful storm tracking over the Great Lakes that brought a deadly outbreak of severe weather and strong tornadoes to the Deep South will continue tracking northeast over the Great Lakes. A warm front and cold front associated with this storm could bring thunderstorms, though regardless, dangerously strong winds will be present. After this storm passes, this gives way to a cooling pattern with a second, weaker storm coming Wednesday. Temperatures during this period start above normal in the 60s to below normal in the low-50s.
Rest of today – a powerful surface low over tracking over the Great Lakes with minimum central pressure below 984 mb will bring a period of dangerous winds to the region. The pressure gradient between this low and high pressure over the Atlantic will be very tight, as you can see below. This will result in sustained winds easily in the 30 mph range, with stronger gusts of 60-65 mph possible due to the very strong winds aloft. Both the warm front and cold fronts of this storm could touch off some isolated elevated thunderstorms, though instability will be modest at best. High temperatures should peak in the upper-60s with robust warm air advection due to these strong winds eventually turning southwest. Overnight lows in the mid-40s as this storm pulls away.
Weather Prediction Center surface forecast for 2PM Monday
Tuesday – skies clear up overnight into the morning. Partly cloudy to mostly sunny skies should prevail with high pressure building. High temperatures in the upper-50s. Overnight lows around 40°F.
Wednesday – a second, weaker low is forecast to form over the northern Gulf of Mexico along the southerly extremes of the cold front from this first storm. This low then slides northeast along the coast. Although this second storm will pass far to the south of us, it could still bring some rain during the day. With clouds, rain, and an onshore northeasterly/easterly flow, temperatures will struggle to hit 50ºF. Overnight lows in the upper-30s.
GFS model 500 mb height anomalies for 2PM Thursday. Negative height anomalies at the 500 mb level can often translate to below normal temperatures at the surface.
Thursday– temperatures remain cool despite more sun, only reaching into the low-50s. Overnight lows around 40ºF.
We have a stormy start to the forecast period with the Storm Prediction Center putting us under a slight risk for severe weather this afternoon. Behind this storm, windy conditions will prevail Friday with the pressure gradient tightening between an incoming high pressure and the departing low. This pressure gradient eases Saturday as high pressure moves more directly overhead. Decent weather continues Sunday before another storm rolls in Monday. Above normal temperatures for Thursday in the low-60s. Temperatures drop below normal in low-50s this weekend before picking up Monday into the upper-60s.
Rest of today – lighter stratiform rain in the morning hours with a warm front moving through. This will be followed up by a possible round of strong to severe thunderstorms in the afternoon hours (most likely around 1-2PM). The primary risk for severe weather comes from the potential for damaging wind gusts, with very fast winds aloft potentially mixing down to the surface. High temperatures in the low-60s. Overnight lows around 40ºF as gusty winds bring in strong cold air advection. See this detailed forecast for more info about today.
Storm Prediction Center convective outlook for Thursday, showing us in a slight risk area for severe weather later today.
Friday – despite a high in the low-50s, strong winds around a deepening low will make it feel significantly cooler. Clouds should gradually diminish during the day. Overnight lows cool, in the upper-30s.
Weather Prediction center surface forecast for 8AM Friday. A strong low pressure cetner is indicated tracking northeast out of Maine.
Saturday – winds ease as an area of high pressure moves more directly over us. High temperatures should range in the mid-50s with plenty of sun. Overnight lows will be in the mid-40s.
Sunday– clouds increasing with high temperatures in the upper-50s. Overnight lows will warm into the low-50s.
It’s been nearly three months since my last detailed forecast, so forgive me if I’m a bit rusty. Thursday in NYC will be an active weather day. A rather complex picture will unfold, with a warm front passing early, then a triple point passing nearby, followed by a trailing cold front that could bring the potential for thunderstorms later in the afternoon. Strong winds will be in the picture, and these winds will persist (if not increasing in intensity) into Friday.
My Forecast High: 61°F | Low: 49°F | Max sustained winds: 33 mph | Total precipitation: 0.24″ – verification will come from METAR data for the period between 2AM Thursday and 2AM Friday (06Z Thursday to 06Z Friday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.
Verification High: 58°F | Low: 44°F | Max sustained winds: 44 mph | Total precipitation: 0.26″ – this ended up being a decent forecast for the high temperature. The cooler scenario depicted by NAM ended up being correct, and siding with a more conservative high was the right call. Amazingly, I was only 0.02″ off from the precipitation total! However, in my focus on that aspect of the forecast, I neglected some basic signs about the winds and low temperatures. These two ended up being connected. Winds in the wake of the cold front were likely boosted by subsidence (sinking cold air), and these provided a boost to cold air advection, leading to the low actually occurring around midnight, as opposed to the overnight hours going into the day. This was actually apparent in the statistical guidance, but was something I failed to spot. Lesson learned: never forget to check the entire data set – and when cold fronts with convective activity swing through, consider being aggressive about the winds associated both with the storms themselves, and behind the front.
Weather Prediction Center surface forecast for 2AM Thursday
Weather Prediction Center surface forecast for 8AM Thursday
Weather Prediction Center surface forecast for 2PM Thursday
Weather Prediction Center surface forecast for 8PM Thursday
Synoptic Setup At the surface, two lows will be influencing the picture, one centered further north over Ontario, and another tracking closer to the area. Early in the forecast period, a warm front associated with secondary low pushes through. This could lead to some lighter stratiform rain due to isentropic (overrunning) lift. After this, a triple point passes just north of the area in the afternoon, and this should provide a locus for some some enhanced lift. This will be followed shortly thereafter by a trailing cold front passing through in the late afternoon hours. This cold front could trigger some thunderstorms with NAM showing some instability, though GFS isn’t as aggressive.
GFS is less bullish on showing a saturated layer at 850 mb. NAM does have wetter conditions which explains why the QPF totals are higher with this model. One thing both models agree on is the presence of strong winds at this level, anywhere from 35-50 knots. Should moisture content be better upstream, we should see effective moisture transport from this low-leve jet.
Further up in the atmosphere at 500mb, a shortwave trough attached to a closed 500 mb low over Ontario/Quebec border is forecast pivot through the region. Models are suggesting very strong positive relative vorticity associated with this feature. This should lead to ample divergence aloft and enhanced lift potentially supportive of organized convective activity. Low-mid level lapse rates due to the presence of the closed low could also be decent enough to support convection.
Finally, at the 300 mb level, a jet streak with very fast core winds in excess of 140 knots looks to set up over the Ohio Valley. We will be in the favorable left exit region of this jet streak, a set up that further favors enhanced divergence aloft. This should likewise increase lift in the atmosphere. This is reflected by SREF that shows a decent probability of moderate to strong omega over the region during the passage of this storm.
NAM model 850 mb relative humidity and winds valid 2PM Thursday
GFS model 500 mb height and relative vorticity valid 2PM Thursday
GFS model 300 mb height and winds valid 2PM Thursday
High Temperatures There was a large spread between NAM and GFS statistical guidance, with NAM much cooler and coming in only in the mid-50s, while GFS came in with low-60s. Given that there should be some warm air advection with southerly winds ahead of the cold front, I tend to buy more into the warmer end of the guidance envelope. However, both sets of statistical guidance also show a period of winds backing to the ESE in the afternoon which would bring a characteristically onshore flow and introduce a marine air mass. That might cut into overall high temperatures. Some limited evaporational cooling and clouds could also keep a cap on temperatures warming too much. With all this in mind, I’m going with a high temperature of 61ºF.
Low Temperatures There is likewise a big spread between GFS and NAM on low temperatures. NAM is close to climatological averages for low temperatures in the low-40s while GFS is a full 10ºF warmer. Southerly winds are indicated during most of the overnight hours seem to suggest erring on the warmer end of guidance. I think that EKDMOS 50th percentile of 49ºF seems reasonable.
GFS MOS guidance for KLGA
NAM MOS guidance for KLGA
Max Sustained Winds Both GFS and NAM indicate that a well-mixed layer will form by the late afternoon. As referenced above, winds aloft at 850 mb will be quite strong. This mixed layer should enable these strong winds to work their way down to the surface. This will be aided by any downward momentum transfer effected by falling rain. Layer mean wind analysis shows max wind speeds well above statistical guidance, and I few reasons to disagree with this, so I’m calling for max sustained winds of 29 knots, or 33 mph.
GFS forecast sounding for KLGA valid 2PM Thursday. The presence of a well mixed layer is apparent from the surface up to just above 850 mb. This should allow for strong winds at this layer to mix down to the surface, something that would be enhanced by precipitation drag effects from rain falling.
Total Precipitation There is high bust potential for total precipitation forecasts here with convective precipitation in the picture. The earlier light stratiform precipitation with the warm front probably will not result in too much overall precipitation. However, just one strong thunderstorm/heavy downpour could wreck any forecast here. The blended GFS/NAM mean is about 0.25″ and SREF probabilities for precipitation greater than this are not a lock, despite the overall synoptic picture showing decent support for good lift. SREF gradients are quite sharp going south. In addition, onshore winds that are possible could help stabilize the area by bringing in a cooler marine layer. I don’t feel confident that we’d see more than 0.25″ unless a convective burst hits KLGA head on, so I am going with 0.24″ as a conservative play.
We have above normal warmth to start the week in the mid-60s. Clouds increase Tuesday going into Wednesday as a low is forecast to form along a warm front. This brings us the first chance for rain Tuesday night into Wednesday morning. There appears to be a brief pause in rain chances before before a more potent storm passes Thursday. As pointed out by forecasters, this storm looks to be associated with a vigorous upper low that should enhance lift. Some thunderstorms could be possible with this.. Temperatures will trend lower towards end of week.
Rest of today – high pressure in control with plenty of sun, high temperatures should rise into the mid-60s with downsloping northwesterly winds. Overnight lows in the mid-40s.
Weather Prediction Center surface forecast for 8PM Tuesday
Tuesday – a warm front associated with a low tracking into the Great Lakes makes its approach. Ahead of this low, clouds will increase, though temperatures should still be able to reach into the low-60s. Overnight lows around 50°F with rain chances increasing.
Wednesday – rain early in the day as the warm front lifts through the region. High temperatures still reaching into the low-60s. There may be possible partial clearing of skies in the afternoon as we get into the warm sector behind the warm front. Overnight lows in the upper-40s.
GFS model 500 mb height, and relative vorticity valid 2PM Thursday. This model depicts a closed upper low over the Great Lakes spawning very strong vorticity (and hence divergence and lift aloft).
Thursday– a second, more powerful storm hits the region. A closed upper low over the Great Lakes will provide enhanced lift for this storm as it pushes a cold front through the area later on Thursday. High temperatures in the upper-50s. Showers and possibly thunderstorms will accompany the cold front passage. Overnight lows in the low-40s.
A retrograding low will bring increasing clouds, wind and rain to end the week. This low will be blocked from moving east until late Friday. High pressure will move in Saturday and should dry things out, and bring more sun. A weak cold front is forecast to pass through Sunday. Some rain will be possible with this frontal passage. Temperatures during this period should remain at or above normal for this period in the mid-50s.
Rest of today – increasing clouds with a low retrograding west towards the area. High temperatures in the mid-50s. Winds will pick up also as the pressure gradient builds between the retrograding low and high pressure to the west. Overnight lows should be around the mid-40s.
Friday – chances for rain, mostly in the morning hours, with high temperatures in the mid-50s under mostly cloudy skies. Rain chances will diminish as this low finally pulls off to the south. Overnight lows again in the mid-40s.
Weather Prediction center surface forecast for 2AM Friday
GFS model 500 mb height, vorticity and wind forecast valid 10AM Thursday. Note the presence of the closed upper low offshore of the Northeast, with an omega blocking pattern over the eastern Atlantic (two lows, with a ridge in between, literally looks like the Greek letter for omega)
Saturday – as high pressure moves in, we’ll see a better day with partly to perhaps mostly sunny skies and high temperatures in the upper-50s. Overnight lows will be in the mid-40s.
Sunday– a weakening cold front may bring a chance for showers, but ahead of this, temperatures will be mild in the upper-50s. Overnight lows will warm into the mid-40s.
