Jul 22

**Limited Blog Updates July 22-August 2, 2014**

** BLOG NOTICE: Between July 22 and August 2, 2014, updates will be posted less frequently, at least every two days but may vary at times. Daily updates to the blog, along with the 8-day outlook, will resume on Saturday, August 2. **


Jul 24

July 24, 2014 Brief Update

Forecast Overview:


Posted above from left to right are the latest available surface analysis and radar composite from the NWS Weather Prediction Center (WPC), and the initialized GFS 500 hPa heights and vorticity from NCEP MAG; both are valid at 06Z Thursday UTC (8:00 AM Thursday EDT). A cold front moved through the area last night, having previously produced heavy thunderstorms over parts of northern New Jersey, NYC and southeast NY in the evening and early overnight hours. Temperatures peaked in the upper 80s to low 90s away from the coast with humid conditions yesterday. Followed the passage of the cold front, a cooler and less humid air mass is expected through Saturday, with highs in the low to mid 80s.

More significant changes in the upper level flow will occur on Sunday and next week as a strong upper level low, separate from the polar vortex center north of Greenland, becomes stationed over southern Canada due to upper level ridging extending to its north over central-northern Canada and a persistent ridge in the western US, continuing the hot and dry pattern in the West Coast. This will lead to a persistent trough setting up near the central and eastern US, continuing this summer’s trend for a lack of heat in the northeast US relative to the last few years. A potent shortwave trough near Washington state will progress east, reaching Michigan on Sunday while aiding in the development of a surface low pressure. Additional weak shortwaves are likely to approach Pennsylvania on Sunday ahead of the main trough, leading to widespread coverage of rain and thunderstorms. The first shortwave moving through on Saturday night may result in scattered thunderstorms overnight, primarily from NYC and further north and west, with indications of a potential lull in the thunderstorm activity in the afternoon as drier air moves through in the mid levels before the main shortwave trough over Michigan enters the region, providing sufficient forcing to maintain locally heavy rain and thunderstorm activity as it moves through the area between Sunday evening and Monday morning. The possibility of scattered showers remains through at least Monday evening. The exact timing remains somewhat uncertain at this time, and some changes may be possible over the next few days.

A brief surge in warmth and humidity is expected for Sunday and Monday, with highs in the mid 80s away from the coast and dew points likely near the upper 60s, while a southerly wind again keeps coastal Long Island and Connecticut with cooler temperatures in the upper 70s to low 80s. Following the passage of the cold front on Monday, a cool air mass will slowly move through the region with 850 hPa temperatures likely near 8-10C; with the expectation for mostly sunny skies and a downsloping northwesterly flow, however, the latest outlook sides slightly warmer than the model guidance with high temperatures in the upper 70s inland and low 80s elsewhere. Overnight lows may fall into the 50s away from NYC and the immediate coast. Looking into the longer range through the first few days of August, a slow warming trend is expected as the upper level trough lifts north of the region, with increasing humidity likely as well with an overall south-SW flow.

The next full forecast discussion is scheduled to be posted on Saturday. The limited posting schedule will continue through August 2, when updates are scheduled to be resumed on a daily basis.

Jul 21

July 21, 2014: Brief Warmth, Humidity This Week

Forecast Highlights:

temp36Following a cooler than average weekend with highs generally in the mid 70s to low 80s, an increase in warmth and humidity is expected through Wednesday, with highs reaching the low 90s in parts of the area, before a cold front moves through early on Thursday with a risk of thunderstorms. A drier ending to the week is anticipated, but with a continuation of a lack of heat in the region along with a chance of rain through next week (image credit: PSU e-Wall, modeled highs on Tuesday).

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Jul 17

July 17, 2014 Brief Update

Forecast Overview:


Posted above from left to right are the latest available surface analysis and radar composite from the NWS Weather Prediction Center (WPC), and the initialized GFS 500 hPa heights and vorticity from NCEP MAG; both are valid at 06Z Thursday UTC (8:00 AM Thursday EDT). The cold front which continued to produce rain through yesterday morning is east of the area, slowly progressing to the east, with a broad area of high pressure to provide the region with mostly sunny skies through Saturday. Daytime highs are expected to peak in the low to mid 80s, while overnight lows are cooler than average, especially inland towards interior northwest NJ, southeast NY and Connecticut away from the coast, where clear skies and light winds should allow temperatures to fall into the mid to upper 50s, falling close to 50 degrees in localized spots.

Otherwise, the weather pattern over the next week is expected to remain relatively inactive compared with recent weeks, with a lack of strong forcing for precipitation except for a weak shortwave trough which may trigger scattered showers on Sunday, and a potential cold front late next week which may produce another round of scattered thunderstorms. Temperatures are generally expected to remain close to average in the low to mid 80s through Monday, gradually warming up next week with increased humidity as temperatures rise into the mid to upper 80s from Tuesday through the late week, possibly reaching the low 90s in spots in the warmer case scenario. Uncertainty increases towards late next week depending on the setup of a strong ridge over the western US with 500hPa heights rising over 600 decameters, with solutions ranging from a persistent trough on the GFS to the western Atlantic ridging expanding westward through the region on the CMC.

Jul 16

July 16, 2014: Drier, Less Humid End To Week

Forecast Highlights:

gfs_7.16A slow moving cold front which produced heavy thunderstorms and localized flash flooding yesterday is currently moving through New York City, with drier and sunnier conditions returning from this afternoon through the rest of the week along with lower humidity. Temperatures are likely to remain in the low to mid 80s through next Monday before a slow warming trend begins.

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Jul 15

July 15, 2014 Brief Update

Today’s Outlook: More Thunderstorms Today


Posted above from left to right are the latest available surface analysis and radar composite from the NWS Weather Prediction Center (WPC), and the initialized GFS 500 hPa heights and vorticity from NCEP MAG; both are valid at 06Z Tuesday UTC (8:00 AM Tuesday EDT). With a pre-frontal trough near the area yesterday, along with several weak shortwaves moving through the region, scattered heavy thunderstorms affected parts of the area in the afternoon and evening. The severe thunderstorms set up south of the area, however, with some wind damage towards southern New Jersey and Maryland, along with a nearly stationary cell producing over 5 inches of rain in east central NJ, although the thunderstorms that extended into the area in the evening produced heavy rainfall, locally up to 1-2 inches in parts of Long Island, southwest CT, and northern New Jersey. Since then, the thunderstorm activity from last night dissipated, although the cold front associated with a developing low pressure near Michigan is gradually progressing east towards the region.

As with yesterday, widespread cloud cover is expected to limit instability with CAPE of at least 1500 J/kg, although the region will be placed near the right entrance quadrant of an upper level jet streak, while an approaching 500 hPa jet streak will lead to 0-6km shear increasing to at least 40-45 knots in the western half of the area. The greatest overlap between instability and shear is expected to the south of the area, towards southeast PA into Maryland, where the highest probability of severe thunderstorms exists, although discrete thunderstorm cells may develop in the immediate NYC area and northern New Jersey towards 2-4pm this afternoon, some which may become strong or locally severe with strong wind gusts and downpours producing localized flash flooding. A more organized line of thunderstorms is likely to approach the area towards 5-7pm this evening, but with the main risk primarily from heavy rainfall and flash flooding, along with locally strong wind gusts with the stronger thunderstorms.

More information on the longer range outlook will be included with Wednesday morning’s update.

Jul 14

July 14, 2014: Heavy Rain, Storms Today & Tuesday

Forecast Highlights:

rad11A warm and humid air mass remains in place over the region, with both today and tomorrow featuring heavy thunderstorms, potentially severe, capable of producing flash flooding and strong wind gusts. A cold front will slowly clear the area later this week with dry and sunny conditions returning for Thursday and Friday, but with a trough persisting over the region keeping temperatures near or slightly below average by next weekend into next week along with a risk of rain (image credit: PSU e-Wall, HRRR simulated reflectivity this evening).

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Jul 13

July 13, 2014: Warm, Stormy Start To Week

Forecast Highlights:

t0The recent stretch of seasonable and dry weekends will end for parts of the area on Sunday, as a shortwave trough approaches on Sunday, producing scattered afternoon and evening thunderstorms, while temperatures increase into the mid 80s to low 90s with rising humidity through Tuesday. A slow-moving cold front will produce additional rainfall from Monday through Wednesday, with the potential for strong storms and heavy rainfall, followed by a slight cool down at the end of the week.

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Jul 10

July 10, 2014: Storms Possible Early Next Week

Forecast Highlights:

gfs_namer_135_500_vort_htSeasonable temperatures and dry conditions are expected from today through Saturday as temperatures generally peak in the low to mid 80s away from the coast. Increasing cloud cover is expected by Sunday along with a risk of strong to severe thunderstorms on Monday and Tuesday, along with a heavy rain potential, followed by a cooler and drier ending to next week (image credit: NCEP MAG, 0z GFS modeled 500hPa heights early next week).

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Jul 09

July 9, 2014: Week Ends on Cooler, Drier Note

Forecast Highlights:

temp12Warm temperatures will continue today again, but with decreasing humidity as a cold front gradually moves through, with a cooler and dry ending to the week anticipated. Seasonable conditions will continue through Saturday, but with increasing probabilities of rain and thunderstorms from Sunday evening through Tuesday ahead of a cooler air mass likely to provide the region with near to slightly below average temperatures through the rest of next week (image credit: PSU e-Wall, 4k-NAM modeled highs today).

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