Archive for rain threat
Heavy rain threat developing for Saturday
Posted by: | Comments07/08/10 5:30 PM
The heat wave that brought record breaking temperatures has been broken, however the humid, muggy conditions remain.
An upper level low that has been meandering off the Mid Atlantic coast is now migrating north this evening towards the North Carolina coast. This upper low is transporting a warm, moisture saturated air mass from the Tropical Atlantic right into the northern Mid Atlantic. Thus, while temperatures have fallen off into the 80′s and 90′s, the dew points have remained in the 60′s and 70′s, which leads to a very humid conditions.
Now, there is an interesting set up developing for the northern Mid Atlantic this evening that will play a major role in this weekend’s weather. As I stated above, the upper low is transporting a humid air mass right into the region. Meanwhile, a very slow moving cold front is approaching from the west. As the cold front moves closer, low and mid level lifting will increase due to the winds converging over the northern Mid Atlantic. When winds converge at the lower and mid levels, lifting can become rather intense.
As such, the threat for showers and thunderstorms will increase through tomorrow and into Saturday with the apex being when the cold front finally moves through the New York City and Philadelphia metropolitan area on Saturday evening. This cold front will produce a line of showers and thunderstorms capable of very heavy downpours. Given the speed of the cold front, which will be slow, these showers and thunderstorms are likely to remain over the same location for several hours, so there is an increasing potential for localized flooding on Saturday evening.
More thoughts and details on what could be the best rainfall this region has seen in over 3 months, tomorrow morning!
-- Weather When Posted --
- Temperature: 82°F;
- Humidity: 58%;
- Heat Index: 84°F;
- Wind Chill: 82°F;
- Pressure: 30.04 in.;
Clearing skies and breezy conditions
Posted by: | Comments7:20 AM
A strong coastal low over the Gulf of Maine this morning will interact with high pressure over the Ohio Valley producing breezy conditions through the early afternoon hours as a strong pressure gradient will remains in place. Winds will range from 10 to 20 mph from the northwest with gusts to 30 mph at times through the afternoon hours. Otherwise, skies will slowly clear as dry air works in from the west into the Philadelphia and New York City metropolitan area.
High pressure will remain in control through tomorrow afternoon with dry conditions, scattered clouds, and temperatures averaging near normal in the 50′s and lower 60′s.
However, the next rain threat is already pushing into the southern Plains as a strong Sub Tropical disturbance comes east. This disturbance will interact with a cold front from the Polar jet stream. On Thursday night, clouds will rapidly increase followed by rain, heavy at times, late on Thursday night. This low pressure system will track from the Mississippi Valley towards the Delaware coast by Friday morning with steady rain expected throughout the region. The cold front will act force this low pressure system to exit quickly on Friday morning with rain ending from northwest to southeast along the cold front boundary. As the rain ends, snow will mix in over higher elevations however no significant accumulation is expected.
High pressure will return on Friday afternoon with clearing skies. Tranquil yet cool conditions will continue on Saturday and Sunday as the high pressure system moves overhead. However, another area of low pressure is expected to impact the northern Mid Atlantic on Monday with period of heavy rain which is expected to linger into Tuesday morning.
A significant warming trend is expected to develop Tuesday as a Pacific air mass moderates over the Ohio Valley. However, there is a threat of a back door cold front that may limit the extent of the warm air mass along the immediate coast. A significant thermal gradient is possible between the immediate coast and locations just inland.
-- Weather When Posted --
- Temperature: 44°F;
- Humidity: 60%;
- Heat Index: 44°F;
- Wind Chill: 37°F;
- Pressure: 29.73 in.;
Spring-like conditions return!
Posted by: | Comments4:54 PM
It’s amazing how much weather conditions can change in less than 24 hours! Just this morning, overcast conditions dominated and the regions was still soaked from the five day rainfall event! This afternoon, conditions could not be much different with clear skies and much warmer temperatures as highs blew past forecasted temperatures into the upper 50′s to mid 60′s throughout the Philadelphia and New York City metropolitan area.
The ability for this new air mass to warm could not be clearer and given that this air mass and the tranquil weather conditions are expected to remain over the northern Mid Atlantic through the end of this week and into the weekend, I have significantly bumped up expected high temperatures throughout the rest of this week. I know think that this weekend has the potential to experience temperatures in the mid to upper 60′s, especially over the Delaware River Valley. I could even make a case for a 70 degree high somewhere around Philadelphia, but I think this will be a rather rare and isolated observation at most.
The next rain threat returns to the region on late Sunday night into Monday morning in the form of a slow moving cold front. This cold front will be able to produce periods of heavy rain and embedded thunderstorms. The thunderstorms may approach severe levels if the air mass ahead of this cold front on Sunday afternoon becomes significant unstable, which is something to keep an eye on. Otherwise, given the state of the area’s rivers, the potential for heavy rain will enhance flash flooding concerns once again.
High pressure returns once again for Tuesday and Wednesday, but this time a Polar air mass will take hold with significantly cooler temperatures throughout the northern Mid Atlantic. High temperatures will return to the 40′s and 50′s once again for Tuesday and Wednesday as a result.
-- Weather When Posted --
- Temperature: 59°F;
- Humidity: 21%;
- Heat Index: 59°F;
- Wind Chill: 57°F;
- Pressure: 29.95 in.;
Heavy rain for tomorrow morning, winter returns this week
Posted by: | Comments9:26 AM
There is no doubt that heavy rain is on the way as a significant surge of moisture races north ahead of a powerful cold front.
Clouds will continue to increase and lower through the day as a strong southwesterly flow from the surface to mid levels pushes a warm and moist air mass into the region. Temperatures will average above normal through the next 24 hours with temperatures rising through the 40′s and into the 50′s this evening and overnight. Rain will begin to push into the Philadelphia metropolitan area late tonight around mid night and continue to move east through the New York City metropolitan area early tomorrow morning.
The rain will be very heavy at times, producing flash flooding and rapidly reduced visibility through the morning rush hour. Combined with the heavy rain threat will be embedded thunderstorms within the rain shield that will lead to strong wind gusts possibly pushing over 40 mph at times. A strong 850 MB jet streak around 3o KT to 45 KT will support isolated downbursts within these thunderstorms. The rain will be heaviest from 6 AM to 2 PM with rainfall amounts ranging from one to two inches of rain. Flooding of streams, small rivers, and urban locations are likely from this cold front passage. The cold front will exit by tomorrow afternoon between 2 PM and 5 PM with temperatures rapidly falling through the 50′s, 40′s and 30′s with morning lows on Tuesday morning in the 20′s and 30′s.
Once the cold front passes, a new pattern will become established with a return to much colder conditions mirroring the temperature profile of early January. Temperatures on Tuesday will still average near normal with the immediate coast approaching 40 degrees. However, from Wednesday through Friday temperatures will average below normal with highs in the 20′s and 30′s throughout the region. A series of weak cold fronts will keep the threat of scattered snow showers in the forecast through the week with some minor accumulations in isolated locations.
The main story is the developments at the end of the week. Model guidance is strong converging on a solution that will bring a potentially significant snowfall to much of the northern Mid Atlantic. This storm appears to develop in two parts. The first is an isentropic lifting driven snowfall with a thermal gradient at 850 MB over 12°C and a surface gradient forecasted to range from 20° F on Friday afternoon to over 30° F on Friday night from the coastal waters to the interior. This strong thermal gradient will be set up ahead of the actual coastal low development on early Saturday morning, and strongly argues for an impressive isentropic lifting environment. Model guidance is attempting to forecast the potential snowfall for this scenario, but likely is under-forecasting the potential influence of frontogenesis and mesoscale lifting parameters like banding of precipitation. This gradient also strongly argues for a rapidly unstable atmosphere and thunder snow may have to be considered on Friday evening given the atmospheric set up.
The coastal low takes over as the dominant feature of this storm on Saturday morning with heavy snow focused along the immediate coast. The exact track of this storm is still uncertain and will be an important detail, however a significant majority of the guidance strongly suggest that the atmosphere will support an all frozen if not all snow event for this storm. A significant snowfall from Friday afternoon through the day on Saturday is growing and looks likely.
-- Weather When Posted --
- Temperature: 33°F;
- Humidity: 86%;
- Heat Index: 33°F;
- Wind Chill: 27°F;
- Pressure: 30.2 in.;
Tracking Another Rain Storm For This Summer
Posted by: | Comments
The latest updates can be found at the bottom!
8:36:31 AM: The steady rain is close to coming to an end as the back end of the heavy rain moves through eastern Pennsylvania.
8:37:32 AM: The occluded front is still off to the west of the region and will continue to slowly progress eastward through the afternoon.
8:38:03 AM: Scattered showers are currently developing over much of central Pennsylvania and will continue to move east through the afternoon hours.
8:38:37 AM: I expect the steady rain to come to an end from west to east starting by 9:30 AM and exit the coast by around 2 PM east of Long Island.
8:39:07 AM: The occluded front and low pressure system should move east of the forecast area by this evening, which will put an end to the rain threat.
8:40:05 AM: The overcast conditions back through central Pennsylvania will prevent the atmosphere from destabilizing.
8:59:09 AM: Through this past hour, there is a wide variety of rainfall amounts from this system ranging from a little over a 0.10″ to as much as 2″!
8:59:37 AM: The heaviest rain has fallen over the central Hudson Valley towards Albany where the upper level lifting has been strongest.
9:00:26 AM: Meanwhile, portions of NE PA has received as much as a half an inch of rain, especially along the Delaware River.
9:23:18 AM: The steady rain is coming to an end over Wayne, Monroe, Carbon, Lehigh, Berks, Chester Counties of PA. Scattered showers remain a threat.
10:27:08 AM: Steady rain has ended in Philadelphia and much of eastern PA. Steady, heavy rain will continue for much of NJ and NYC metro through 12 PM.
10:29:37 AM: Much of Long Island will have heavy rainfall through at least 3 PM with rain tapering off by 5 PM over eastern Long Island and Connecticut.
10:36:47 AM: Doppler estimated rainfall rates with this finally heavy band of rain range from 0.25″ to 0.50″ per hour with isolated amounts to 1″/hr.
12:17:24 PM: Scattered showers and isolated thunderstorms are starting to develop over central and eastern PA.
12:18:51 PM: Most of the thunderstorms will be weak, however a few isolated thunderstorms could become strong just ahead of the low pressure system.
12:20:09 PM: The strongest thunderstorms will be capable of occasional lightning, small hail, very heavy downpours, and wind gusts up to 50 mph.
2:40:51 PM: The steady, heavy rain is just about over for Passaic, Bergen, Essex, and Hudson Counties for NJ and New York and Bronx Counties of NY.
2:41:47 PM: The rain will continue to progress move ENE through the afternoon with rain exiting Long Island and Connecticut by around 4 to 6 PM.
2:42:56 PM: Scattered showers and isolated thunderstorms are still moving through E PA and much of New Jersey.
2:43:29 PM: However, these showers and thunderstorms are weakening and will continue to do so as the afternoon progresses.
2:52:56 PM: An Urban Flood Advisory has been issued for Suffolk and Nassau Counties of NY due to rainfall amounts of half an inch per hour.
2:52:56 PM: An Urban Flood Advisory has been issued for Suffolk and Nassau Counties of NY due to rainfall amounts of half an inch per hour.
2:59:29 PM: A Coastal Flood Advisory is in effect through 7 PM to 12 AM for shore lines of the Delaware River around Philadelphia.
3:00:17 PM: The persistent southeast wind will continue to push water from the Delaware Bay into the Delaware River, which will cause minor flooding.
3:01:48 PM: The stable nature of the atmosphere is limiting the strength of thunderstorms moving east into the forecast area.
3:02:27 PM: While the southern Mid Atlantic will see severe weather this afternoon, I only expect scattered showers and an isolated strong thunderstorm.
5:19:10 PM: For the rest of the afternoon and evening, expect scattered showers to continue to move through the forecast area.
5:19:39 PM: The steady rain will continue over eastern Long Island and Connecticut through the late evening hours.
5:20:05 PM: However, the majority of the steady rainfall is over for the NYC and Philadelphia metros.
5:20:55 PM: Upper level energy rotating through the forecast area this evening will support showers with brief periods of moderate rainfall.
5:21:19 PM: Much drier conditions are expected tomorrow, especially in the afternoon.
-- Weather When Posted --
- Temperature: 62°F;
- Humidity: 93%;
- Heat Index: 62°F;
- Wind Chill: 61°F;
- Pressure: 29.87 in.;
Freehold
77°
Philadelphia
81°
Sussex
73°
Allentown
77°
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