Philly weather: Expect flood, wind watches up ahead of nor'easter

With the threat of a long-duration nor'easter, the National Weather Service has posted a flood watch for most of the region from 1 a.m. Friday until daybreak Saturday, and warned of wind gusts up to 60 mph in South Jersey.

Working in tandem with the full moon, the storm forecast to explode off the Mid-Atlantic could generate minor flooding during the Friday morning high tide, and perhaps major flooding with the Saturday morning and evening high tides. A coastal flood watch is in effect from late Thursday through Saturday evening.

The conditions would represent a dramatic contrast to the last few days — the temperature at Philadelphia International Airport hit 60 on Wednesday — a fitting conclusion to an extraordinarily balmy February. By day's end, the month will have become the third-warmest February in 145 years of record-keeping, with an average temperature of 41.9, or 6.2 degrees above the long-term normal.

The month's average temperature here  — and elsewhere in the East  — was bumped up by the incredible warm surge of Feb. 20-21. On the 21^st, the temperature hit 82 in Washington and 75 in Syracuse, N.Y. For the month, heading into Wednesday, Boston was at 6 degrees above normal; New York, 6.6, and Burlington, Vt., 8.5.

While almost snow-less  —  just 1.4 inches at Philadelphia International Airport — February also will rank as the fifth-wettest with just over half a foot of precipitation.

This is not the year (perhaps not even the century) to trust long-term models, but the approaching storm might signal that the first half of March looks as if it won't be resembling the last half of February.

The region won't be experiencing the unusual cold and snow that have invaded the British Isles and Western Europe, but the Mid-Atlantic and Northeast coasts are about to weather the strongest nor'easter since the January "bomb."

Once the storm ripens off the coast, it would be in no hurry to move.

That's because for the first time in weeks, a major "blocking" pattern has taken residence, with cold high pressure centered in the vicinity of Greenland. That's helping to drive a taste of Siberia into the Emerald Isle and England.

The technical label for this pattern is the negative phase of the North Atlantic Oscillation, not that names matter. What matters in the short term is that it's going to slow things down.

The Climate Prediction Center sees the pattern persisting and says the odds favor below-normal temperatures the next two weeks around here.

If the month finished near normal, March would have a decent shot at being colder than February for the second year in a row. The normal March temperature is 43.5.

So much for that. Before the precipitation shuts off this weekend, the interior Northeast, and perhaps even the Philadelphia region, could see snowflakes, with up to 5 inches in the Poconos.

Here are the five warmest Februaries in Philadelphia: 2017, 44.2 degrees; 1925, 42.2; 2018 (projected) 41.8; 1998, 41.8; and 1980, 41.4 degrees.