Sep 23

Sept 23, 2014 Morning Update

Forecast Update: Rain Possible on Thursday

The previous forecast discussion posted two days ago, on Sunday, noted that a coastal low pressure was forecast to develop off the coast, but with a prolonged sunny and dry period likely barring any significant change with the model guidance. Trends over the last day have done just that, and introduce widespread cloud cover, chilly temperatures and possible rain on Thursday, interrupting the stretch of sunny and dry conditions which will resume again for Friday through next weekend.

6z GFS hour 54, valid at 12z Thursday (8am EDT), depicting a weak low pressure south of NYC with heavy rain extending into the area. This run is near the wetter end of the model guidance this morning, with the ECMWF drier but continuing to trend wetter for the area (image credit: PSU e-Wall).

f54As the previous update noted, the coastal low was forecast to develop well off the coast due to sufficient forcing ahead of a weak cutoff upper level low and the favorable positioning of an upper level jet streak off the East Coast. The intensity of the surface low has not changed, progged to remain relatively weak with minimum pressure near only 1016-1020 hPa but with sufficient lift and mid level warm air advection combined with a plume of tropical moisture from the Atlantic Ocean to produce heavy rainfall. What has changed, however, is the track of the low pressure, as in the short term, the model guidance trended stronger with low-mid tropospheric ridging near Bermuda, to the east of the low pressure, forcing it on a more northerly track closer to the coast. This system will likely at least produce widespread cloud cover and chilly high temperatures in the 60s on Thursday, along with a chance of rain between Wednesday night and Thursday afternoon. The northward extent of the heavy rainfall remains uncertain, as this system is capable of producing over 1 inch of rain, but with the NAM and ECMWF near the drier end of the model guidance with below 1/2 inch of rain, and the GFS and CMC on the wetter end of the guidance with 1 to 2 inches of rain.

Additional data is needed to complete a more detailed and thorough analysis, especially considering the volatility of significant trends in the model guidance; one such example is mid-October 2013, when the model guidance trended towards a significant coastal low pressure with heavy rain in the NYC area in the relatively short term, but with the rain ultimately remaining south of the area. Stay tuned for an afternoon update analyzing the expected scenario for Thursday in more detail.

Sep 21

Sept 21, 2014: Prolonged Sunshine & Dry Period Expected

Forecast Highlights:

gfs_namer_120_500_vort_htA weakening cold front is currently moving through the region, its rainfall limited by a deepening coastal low east of the area. Following the passage of the cold front, which is likely to leave most of the area dry, a strong high pressure will set up over the region, providing at least a week-long stretch of mainly sunny skies and near to above average temperatures from Tuesday through the weekend and early next week.

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Sep 19

Sept 19, 2014: Dry, Sunny Pattern Ahead

Forecast Highlights:

gfs_namer_141_850_temp_mslp_precipThe recent dry pattern is forecast to continue through the foreseeable future as the only rain-producing system in the forecast range, on Sunday night, will mostly dry up to the west with only isolated showers possible, bringing a quick end to a weekend warm-up with highs in the 70s and low 80s. A broad upper level ridge will settle overhead from Tuesday, with sunshine, near to above average temperatures and no rain in sight through the rest of the forecast range.

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Sep 17

Sept 17, 2014: Warmer Weekend, Rain Possible Next Week

Forecast Highlights:

gfs_namer_096_850_temp_mslp_precipTemperatures will remain in the low to mid 70s through Thursday, when a cold front will usher in cooler temperatures with highs struggling into the upper 60s on Friday. Temperatures will quickly warm into the 70s and low 80s by the weekend, followed by the possibility of rain early next week and another round of chilly temperatures.

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Sep 15

Sept 15, 2014: Cool Temps Peak During Late Week

Forecast Highlights:

nam-hires_namer_027_sim_reflectivityFollowing a high pressure which provided the area with cool temperatures last night, highs will generally remain in the mid 60s to low 70s range this week with some rain expected on Tuesday. The cool temperatures are forecast to peak on Friday, followed by a brief warming trend in the weekend and a risk of rain on Sunday or Monday, with temperatures otherwise remaining near to slightly below average.

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Sep 12

Sept 12, 2014: Chilly Temps Continue Next Week

Forecast Highlights:

gfs_9.12Following last night’s frontal passage, more sustained cooler temperatures will return into the region, with today’s temperatures only warming up into the low to mid 70s. The drier than normal pattern continues through the foreseeable future, however, with scattered showers likely on Saturday and Tuesday, which will also be accompanied by cooler temperatures in the mid 60s to low 70s.

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Sep 10

Sept 10, 2014: Cooler Weekend Expected

Forecast Highlights:

nam-hires_namer_018_sim_reflectivityA brief warm up will continue today and Thursday, peaking with temperatures in the low to mid 80s ahead of a cold front on Thursday evening which may produce scattered thunderstorms. A gradual cool down is expected through the weekend and early next week, with rain possible on Saturday afternoon and evening followed by another chance of rain early next week (4k-NAM simulated reflectivity tonight, NCEP MAG).

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Sep 09

**September 9, 2014 Notice**

The blog update for Wednesday, September 10 along with an updated 8-day outlook will be posted in the early afternoon (by 2pm EDT), instead of the morning hours. Morning updates will resume on Thursday.

Sep 09

Sept 9, 2014: Near-Below Average Temps Continue

Forecast Highlights:

cpc_cropped2Mostly cloudy skies and isolated showers are expected to persist today as a weak low pressure remains south of the area, with temperatures remaining in the 70s for highs. Some warming is expected ahead of the next cold front on Thursday, producing scattered evening thunderstorms, followed by a slow cooling trend with near to below average temperatures likely to persist through the middle of next week (image credit: CPC, temperature anomalies in the 6-10 day range).

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Sep 08

Sept 8, 2014: Rain Possible Late This Week

Forecast Highlights:

nam-hires_namer_024_sim_reflectivityFollowing Saturday’s cold front, more sustained cooler temperatures will return this week, generally peaking in the 70s except for Thursday when low 80s are possible. Showers are possible on Tuesday, as well as the Thursday evening to Saturday time frame ahead of another cold front, which is likely to be followed by an even cooler air mass for next weekend.

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