Feb 23, 2013: Tuesday Storm To Produce Rain, Snow, Wind

Forecast Highlights:

A weak storm continues to affect the region today with light rain and some snow for interior locations. Mainly to mostly cloudy skies will continue tonight and tomorrow with light rain showers expected to continue especially in Long Island and CT tomorrow, accompanied by warmer temperatures in the 40s for Sunday and Monday. The next storm will then affect the area on Tuesday night into early Wednesday, producing moderate-heavy rain, strong wind gusts, and potentially snow/sleet for interior areas.


Tonight – Monday: Storm Ends, Seasonable Temperatures

Tonight’s storm marks the end of the forecasting of a storm the model guidance has not handled well; only 2-3 days ago, the models were generally in agreement on a significant storm across the region with heavy rain in the area, a snowstorm north/NE of NYC, and significant snow totals in New England over 10-12 inches in locations now barely expected to receive 2-6 inches of wet snow. Until a few days ago, the models incorrectly handled the location and timing of the weakening primary low over the Great Lakes and the shortwave currently moving through the region and showed a slightly more amplified flow in the northeastern US than actually observed, with a stronger low pressure tracking to the NNE just off the coast and intensifying enough for a major precipitation event; the end result was a slightly more zonal flow, with the storm taking a further south track with less precipitation for the region.

The blog updates over the last few days pointed out the model trends with caution, noting that despite the models being in agreement on a significant storm, that agreement was still subject to change, with a weaker storm one of these possibilities; even with these changes, however, my expectation for a moderate event busted on the high side as the storm ended up even weaker and further southeast than originally thought. Last night’s update mentioned the storm was expected to be further southeast and weaker; aside from Connecticut and southeastern New England, only light precipitation affected other parts of the area, with Central Park having recorded around 1/4 inch of rain so far.

Short Range Forecast: As the weak low pressure continues to steadily intensify while moving northeast, mainly cloudy skies will persist across the area tonight; isolated showers are expected from NYC and further west, but with the focus of the light rain towards Long Island and southern CT. Mostly cloudy skies are expected on Sunday especially from NYC and further west, with scattered showers likely persisting over Long Island and Connecticut. Warmer temperatures are expected, peaking in the low to mid 40s in NW NJ, SE NY, and southern CT, and mid to possibly upper 40s in Long Island and the immediate NYC area. Similar temperatures are expected on Monday but with mostly sunny skies.

Tuesday – Wednesday: Storm Produces Heavy Rain, Wind, Some Snow

Another major storm is expected to develop in the south central US on Monday, producing widespread rain, snow and severe weather in that region, which will then track northeast and affect the region on Tuesday and Wednesday. With the current storm, there was a weakening primary system and a second low pressure that developed too far south/east and continued tracking offshore; in this case, however, the low over the Great Lakes region will remain dominant, with widespread moderate to heavy precipitation tracking from the southern US into the Mid Atlantic and northeastern US region.

The model guidance is generally in agreement regarding this scenario, although there is still some uncertainty regarding the exact timing and precipitation types. The GFS is currently the fastest model, bringing precipitation in by the mid afternoon hours, while the ECM and NAM are slower, with precipitation starting late in the evening hours. At this time, I sided with a compromise of the two with starting time around the evening, with the steady precipitation ending around Wednesday morning, although this is still subject to minor revisions. Regarding the precipitation types, widespread front end frozen precipitation is expected across the interior Northeast with temperatures initially below freezing; temperatures should be warm enough for most of the area to start out with rain, although locations towards NW NJ, SE NY and western CT are currently in the borderline area and may observe a period of frozen precipitation before a changeover to rain. The ECM is currently the coldest model while the GFS is the warmest, although it has been trending slightly colder with its latest runs. The latest forecast sides towards at least some frozen precipitation for interior parts of the area, although the amount of frozen precipitation to start is subject to some changes.

Forecast for NYC area: The current forecast is for precipitation to develop in the evening hours; most of the area should be warm enough to start out with rain, although NW NJ, SE NY and western CT are likely to see some snow and possibly sleet at the start of the storm with the possibility of light accumulations. Temperatures will then warm up enough for the interior areas to change over to rain as temperatures overnight remain steady or slightly rise across the area. Through the mid overnight to early morning hours on Wednesday, moderate to heavy rain is expected, along with a strong east wind with gusts up to or above 40 mph. The steady rain should clear the area by Wednesday morning with mostly cloudy skies expected, although the high temperature forecast is uncertain depending on how far north the warm front advances during the day; most of the models support high temperatures at least in the 40s for most of the area and 50s in the immediate NYC area, although it is possible these temperatures may have to be adjusted downwards. Stay tuned for more information on this storm.

Longer Range: Strong Trough Expected

Behind the main precipitation event, the mid level low over the Great Lakes will be slow to exit, slowly tracking to the east and reaching the coast by Friday. For the rest of the week, partly to mostly cloudy skies are expected to persist along with scattered precipitation across the region. During this time period, strong ridging is expected to develop towards the western US with blocking extending into southern Greenland and the Davis Strait region, resulting in a deep trough covering the eastern half of the United States. Temperatures will initially remain seasonable with the strongest cold focused well west of the area, with highs still in the low to mid 40s inland and mid 40s for the rest of the area on Thursday and Friday, but are expected to gradually cool down afterwards into early next week. During this time period in the longer range, widespread below average temperatures are expected in the southern half of the US into the Mid Atlantic region, while the area ends up with temperatures near average and the Northeast with above average temperatures. Currently, no model shows any storm affecting the region in the early March time frame, with any storms developing too far east, although as this is still over a week away, changes are still expected with the models and the early March time frame will be monitored for any storm possibility.

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