Jun 07

Philadelphia Area Weather Threat Assessment Forecast (6/8 – 6/22/15)

Good Evening Everyone,

Okay, got the forecast package updated today. This forecast period will feature several chances for severe weather, excessive rainfall and even excessive heat.  This upcoming week we will have a cold front move across the region on Monday, which may produce some severe weather and excessive rainfall on Monday.  Then weather dries out and turns hot and humid Wednesday into Friday.  As we get into the longer range, the type of weather pattern we’ll have is hot and humid airmass with a chance of showers and thunderstorms.  Looks like any cold fronts that try to move out of Canada and into our region will have a tough time moving through the area.  This will be a situation where fronts become stationary and that may make for some active times.  So, yep, I think the weather will be active and on the hot and humid side, which will certainly feel more like summer.  Definitely monitor all NWS official severe weather outlooks and warnings

 

For official outlooks, please check out the following links
– NWS Daily Weather Briefing
– NWS Mount Holly NJ Facebook
– NWS Mount Holly, NJ Twitter

 

Weather Threat Assessment Forecast
Monday, June 1st through Monday, June 15th

Southeastern Pennsylvania, Southern New Jersey, Northeast Maryland,
and Northern Delaware

Issued Sunday Evening, June 7th  

 

 

5 Day Forecast Period
Monday, June 8th through Friday, June 12th 

 

Weather Threat Forecast Tables
(Click on the hyperlinks below to access the images below) 

Note: Table Legend: Forecaster Confidence Level, Severity Event Index: Minor, Significant, Major, Extreme

 

Forecast Discussion

  • Basic Pattern Overview
    • The model ensemble trends of the last several days favors an upper air trough over the Great Lakes.  In time, this trough will lift out some and replaced with some upper level ridging.  What this means with the trough nearby is an increased threat excessive rainfall and severe weather for Monday into early Tuesday.  Then as the trough pulls back further to the north and ridging takes over aloft, a hotter and more humid airmass will build across the region Wednesday into Friday.     
  • Weather Threats
    • There are three weather threats possible.  
      • For Monday and Tuesday, severe weather and excessive rainfall appear possible.  For the severe weather threat, I’m expected it to be minor.  My confidence level on this threat is medium. The trigger for this action will be a cold front that will approach the area late Monday.  Latest indication is that the front will slow a bit as it tries to move through the region Monday night.  The primary severe weather threat will be damaging winds (60 mph or greater) and large hail (1″ or greater).  There may be a tornado or two possible. This event will be scattered, so not everyone will be impacted by severe weather.  
      • The other main weather threat is excessive rainfall.  For this weather threat, I’m highly confident it will be significant and maybe even major.  As we saw what happen last week, thunderstorms produced prolific rainfall amounts of 3 to 5 in just a few hours ! Even at one point, the Weather Prediction Center put issued a special forecast for 4 to 8 inches due to the front stalling over the area.  So, its definitely something to monitor and keep an eye on. This threat looks to kick in Monday afternoon into the night, especially over Eastern PA. Thunderstorms will likely produce 1 to 2 inches in a short period of time, if not more. The one thing we have to watch for and its one the NWS in Mount Holly pointed out in their forecast discussion is thunderstorms may reform over the same area. Last point, as these thunderstorms produce very heavy rainfall, some roads will get flooded and maybe become impassible.  Please avoid driving areas where they may be flooded.  Plus, the visibility with the heavy rainfall from the thunderstorms may be very low, so please take your time and perhaps pull over until things improve.
  • Weather Ensemble Forecast Maps (Click on the hyperlinks below to access maps)

 

6 to 10 Day Forecast Period
Saturday, June 13th through Wednesday, June 17th

 

Weather Threat Forecast Tables 
(Click on the hyperlinks below to access the images below) 

Note: Table Legend: Forecaster Confidence Level, Severity Event Index: Minor, Significant, Major, Extreme

 

Forecast Discussion

  • Basic Pattern Overview
    • The model consensus shows the jet stream near the US Canada border.  The 500mb anomaly maps show some flat ridging aloft over most of the US.  This type of pattern will bring above average temperatures and precipitation.  This means, the opportunity exists for some severe weather, excessive rainfall and excessive heat.
  • Weather Threats
    • This forecast period favors three weather threats, which are severe weather, excessive rainfall, and excessive heat.  My forecast confidence is medium on all three weather threats. The jet stream will be nearby to allow several cold fronts to try to move down from Canada, but to only stall near the region.  This type of setup will create opportunities for showers and thunderstorms and at times some could be severe and produce excessive rainfall. The other weather threat is the excessive heat.  Temperatures and precipitation will likely to be above average.
  • Weather Ensemble Maps: Click on the hyperlinks below to access maps

 

11 to 15 Day Period
Thursday, June 18th through Monday, June 22nd 

 

Weather Threat Forecast Tables
(Click on the hyperlinks below to access the images below)

Note: Table Legend: Forecaster Confidence Level, Severity Event Index: Minor, Significant, Major, Extreme

  • Basic Pattern Overview
    • The model consensus continues to show the jet stream near the US Canada border.  The European 500mb anomaly ensemble shows even stronger ridging over the Southeastern US. This type of pattern is similar to the 6 to 10 range and will bring above average temperatures and precipitation.  This means, the opportunity exists for some severe, excessive rainfall and even excessive heat. .
  • Weather Threats
    • This forecast period favors severe weather, excessive rainfall and even excessive heat threats. My forecast confidence is medium on all three weather threats again. The jet stream will be a bit further north, but close enough to allow several cold fronts to try to move down from Canada, but to only stall near the region. This type setup will create opportunities for showers and thunderstorms and at times some could be severe and produce excessive rainfall. The other weather threat is the excessive heat.  Temperatures and precipitation will likely to be above average.  

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Background Information

  • I am very excited to provide a new forecast product for the Philadelphia Area, which includes Southeastern Pennsylvania, South Jersey, northeastern Maryland, and Delaware.  In here will be a new experimental product that I’ve produced for the Philadelphia Area.  
  • Right now, I like to issue this product once a week, especially on Sundays. If time permits, I’ll issue a new forecast during the week. 
  • This forecast will aide pretty much everyone from Public, Emergency Management, SKYWARN, and RACES. The idea is to provide everyone with a forecast that gives them the needed lead time to prepare for significant hazardous.
  • Finally, below is further background on my forecast tables and geographic locations
    • Table Legend
    • Forecast Geographic Locations
      • Southeast Pennsylvania: Chester, Montgomery, Bucks, Delaware, and Philadelphia
      • South Jersey: Burlington, Ocean, Camden, Gloucester, Salem, Cumberland, Atlantic, Cape May
      • Northeastern Maryland: Cecil, Kent, Queen Anne’s, Caroline, and Talbot
      • Delaware: New Castle, Kent, and Sussex