June 11, 2013: Heavy Rain, Storms Likely On Thursday

Forecast Highlights:

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The wet pattern continued again today with scattered showers and thunderstorms in parts of the area this afternoon, along with much warmer temperatures compared to yesterday, peaking in the mid 70s to low 80s across the area. Similar temperatures but with more sunshine are expected tomorrow, but the dry conditions will be short lived as a strong storm moves through on Thursday with significant impacts including heavy rain over 2 inches, wind and severe weather.


Tonight – Wednesday: Short Lived Warm, Dry Conditions

Behind today’s scattered thunderstorms, which produced gusty winds and locally heavy rain, dry conditions will briefly return into the area on Wednesday. Mostly sunny skies are expected with highs reaching the upper 70s to low 80s across the area with a breezy NW wind at 5-15 mph.

Thursday – Friday: Heavy Rain, Thunderstorms, Wind Likely

The dry conditions tomorrow will be short lived, as a strong low pressure moves through the region on Thursday into Thursday night. The low pressure will initially develop in the northern Ohio Valley, where widespread severe weather is expected on Wednesday, and will intensify while moving east through the region on Thursday with a minimum pressure likely around 990 to 992 mb, making it an unusually strong low with non-tropical origins for this time of the year; there have not been many similar cases of such a strong low pressure over Pennsylvania and New Jersey of non-tropical origins in June. The strong low pressure will have significant impacts across the region, ranging from heavy rain over 2-4 inches, windy conditions and unseasonably cold temperatures to its north, and hot temperatures with a severe weather outbreak to its south.

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Setup Overview: By this point, all of the models now show rain affecting the region with the CMC the last model to trend north with the storm, as yesterday it showed rain staying to the south. The main area of uncertainty in the storm setup is regarding the track of the low pressure and how far north the warm front advances, which will have an impact on where the heavy rain axis and severe weather zones set up. Currently, the ECM, CMC and UKMET are the southern models, showing 2 to 4 inches of rain across the area with temperatures only peaking in the low to mid 60s before falling into the 50s later into the day. The NAM and GFS, however, trended north throughout the day, showing the low pressure tracking over NYC; the axis of heavy rain is to the north, with 2-4 inches from about Albany, NY into central New England, the warm front stays just to the south keeping the heat and severe weather south as well, with less significant impacts in the area consisting of up to 1-2 inches of occasional periods of rain and thunder. These differences complicate the rain amounts and temperature outlook for the area.

The GFS and NAM have had recurring north biases in cases like this one, especially the NAM which recently showed heavy rains from tropical storm Andrea staying west of the area; normally I would side closer to the ECM, although in this case it may be too far south, as well as the CMC and UKMET. At this time, I am siding between the ECM and GFS, with the low pressure tracking not far south of NYC, keeping the heavy rain axis just north of the area over southeast and central NY into southern New England. The northern half of the area is likely to be in the southern end of the heavy rain axis with 2-4 inches of rain, with 1-3 inches of rain in the southern half of the area, including NYC. Temperatures in the northern half of the area are likely to peak in the low to mid 60s, falling into the 50s by the evening and night hours, and the southern half of the area is likely to peak in the mid to upper 60s. As previously mentioned, however, there is still uncertainty regarding the specifics in the outlook, especially with the rain amounts and temperatures, and the forecast is subject to some changes tomorrow.

 

Outlook for NYC area: Based on the previously mentioned scenario, rain is likely to develop in the area around the mid-late morning hours, becoming heavy at times by the early afternoon. As the warm front makes its closest approach in the late afternoon and evening, rainfall rates may lighten up for NYC and further south as the steady heavy rain shifts north. Heavy rain is expected to continue into the evening and early overnight hours; thunder is possible in NYC around this time, and if the warm front reaches the area, some storms may be strong especially from NYC and further south. Rain is likely to continue overnight, ending around early Friday morning. More localized forecasts can be found in the 5-Day Forecast page.

Significant impacts are expected across the region, with totals as high as 3-4 inches in the axis of heavy rain in New England. For the NYC area, rain totals are likely to end up between 1 and 3 inches, with the lowest totals in the southern half of the area, and the highest totals north of NYC, where totals locally as high as 4 inches are possible, and flash flooding is possible again following the recent heavy rain events. Windy conditions are expected as well, with an east wind at 10-25 mph with gusts up to 30 to potentially 40 mph. So far, Central Park is at 7.99 inches of rain for the month; should this storm produce over 2.25″ in NYC, which is a possibility if the storm takes a more southern track, this month will set the record as the wettest June on record in only 14 days, with another full half month of additional rain events left.

Areas of uncertainty: As previously mentioned, there is still some uncertainty regarding the track of the low pressure, with the forecast still subject to change. Should the current ECM and CMC scenarios verify, steady heavy rain will take place throughout the day and overnight hours with temperatures in the 50s to low 60s along with 2-4 inches of rain across the entire area. Should the north trend continue, rain amounts would be lowered, and the southern half of the area would be monitored for a risk of severe weather, including strong wind gusts. Stay tuned for more information on this storm with a morning update on Wednesday and the final storm forecast in the evening.

Longer Range Update: Dry Weekend, Then More Rain

Behind the Thursday storm, drier conditions will return for Friday and the weekend with mostly sunny skies expected and highs reaching the low to upper 70s on Friday and the mid 70s to low 80s across the area. After the weekend, however, the medium range model guidance shows another low pressure affecting the region with rain and thunderstorms for the early-mid week, which will only add onto what will already be one of, if not the wettest Junes on record. More information will be posted on next week’s outlook over the next few days.

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