Tue 05:03 PM Update — This afternoon’s NAM-NEST, just available, has the heaviest “action” as the front moves into NJ between midnight and 3 AM.  Very heavy rain and high wind gusts possible.

Tue 12:10 PM Update — Heavy rain and gusty winds.  Reviewing this morning’s models, the rain will move in in two main waves.

The first round about 3-4 PM, with the possibility of some thunderstorms.  Available energy (CAPE) is in the low range, so thunderstorms should be not that impressive.

The second round will be between 9 and 1 AM.     The actual front moves through about midnight.  Helicity values very high (>300 J/Kg) with the frontal passage, especially in western suburbs.   High wind gusts (35-40mph) expected ahead of the actual front.  CAPE values low, so thunder not expected with this second round.

NAM NEST Helicity values at 11:30 PM Tuesday.   (Click on image for a larger view.)

Total amount of rain will be 1.25-1.5 inches with some locally heavier amounts possible.


A dip in the jet stream, will usher in a cold front late Tuesday into Wednesday.  Tonight’s models are suggesting the possibility of some heavy rain and imbedded thunderstorms, some could be impressive.

While available energy (CAPE) is on the moderate to low side, other severe weather parameters such as helicity and vertical wind shear are expected to become highly elevated after 10 PM Tuesday evening.  The possibility of thunderstorms with high wind gusts exists.

Heavy rain Tuesday night will reduce to showers that may linger into Wednesday afternoon.

Stay tuned.


Sun 7:45 AM Update — The models are still pointing towards sun breaking through late morning or early afternoon.

The warm front approaching our area will slowly move north of our area through Sunday.  Before that time, we’ll have classic warm prefrontal weather with a weak E or SE wind flow, fog, low clouds and scattered sprinkles or drizzle possible.

The sun breaks through the clouds late morning, 10 AM to noon, according to the the latest NAM NEST and a somewhat later according NBM, but it appears that the actual warm front moves through Sunday evening with additional showers late afternoon and evening.

High temp 78.5° sd 1.5°. Dew points rise to 69-70° It will feel humid.


Sat 11:27 AM Update —  Yet another update.  I knew this forecast was going to be a tough one.  This morning’s HIRESW mode shows these heavy showers that have developed  here late morning, although the model has them arriving about 1 PM.  So it’s going to be difficult to time the showers today.  The Canadian HRDPS didn’t show showers to occur at this time.  More showers, clouds and sun seems to be what’s in store.  
Sat 08:29 AM Update — It’s going to be difficult to time the showers today.  Most of last night’s models (NBM, NAM NEST) didn’t get it right so far this morning. The exception was the high resolution Canadian HRDPS, which matches closely to the showers occurring this morning.   So, continuing with the HRDPS for the forecast, there should be a pause in the showers by late morning or early afternoon.  The early afternoon should continue to be mostly cloudy.  Some more showers possible about 4 PM.

CMC-HRDPS High Resolution model forecast for 8 AM Saturday. Clouds and Precip Rate.  (Click on image for a larger view.)

From last night…

While I post the weather forecasts mostly for storms and weekends, I do look at the models every day.  It’s my daily crossword puzzle. This weekend’s weather forecast has undergone a significant evolution over the past several days.

Originally, Saturday was expected to be dry. Over the past two days, the forecast for Saturday has changed. There’s still some uncertainty about the amount of showers and the degree of cloudiness.

An upper air short wave will move through on Saturday along with a warm front.   Moisture from the south along with the short wave’s vertical lift will result in showers.

GEFS (new model version) forecast for Saturday 2 PM.  The dip in the 500 mb  heights (blue lines) represents the ‘short wave’.

Tonight’s HRRR and HIRESW, just available, suggest even less rain and periods of clouds and some sun for Saturday


  • A mix of clouds and some sun.  Light showers possible throughout the day, although it’s looking less showery. Total precip 0.1 to 0.3 inches of rain.  Showers more likely far western suburbs.
  • High temp 74.6º sd 2.6º (high spread)
  • Winds light SE


  • Cloudy in the morning, sun by afternoon
  • No precip expected, although probabilities a bit elevated west of Philadelphia.
  • High temp 80.1º sd 1.1º   Humid!
  • Winds light SSE to S