Hi all! I tend to only blog when something interesting is in the forecast and with it being December I wouldn’t be shocked if you immediately thought a snow storm was coming. But alas, not this time, Friday’s storm will be all rain and wind and potentially a lot of both.
SET-UP
Wednesday Evening Water Vapor Loop – College of DuPage
Deep tropical moisture is organizing in the Gulf of Mexico and across the southeast in response to an approaching atmospheric trough diving in from the west (evidenced by the southward flow of air from Pacific NW down through the Rockies). An area of low pressure will form in the northern Gulf of Mexico and traverse up the eastern side of the Appalachians from Augusta, GA to Buffalo, NY. Ahead and east of this system very heavy rainfall and extremely gusty winds are expected.
TIMELINE
7 pm Thursday – Tropical Tidbits
By Thursday evening the low pressure is racing northward through the Carolinas. Heavy rain is falling from Greenville, SC to Evansville, IN to Harrisburg, PA. Severe thunderstorms in the form of a squall line are traversing the state of Florida. Wide spread wind damage is likely there.
7 am Friday – Tropical Tidbits
Friday morning the low pressure center has raced its way overnight to Erie, PA. Heavy rain is falling from Cape Hatteras, NC to Burlington, VT. The morning commute in SNE is likely trouble for Connecticut and Rhode Island. The Boston commute may be ok, but it will be close. However the evening commute will likely be a mess. So you may want to consider working from home if you have that option.
1 pm Friday – Tropical Tidbits
During the afternoon on Friday heavy rain will train from south to north into SNE. The occasional clap of thunder may be heard in the heaviest of downpours. Flash flooding is possible; particularly if storm drains remain clogged with leaf litter.
7 pm Friday – Tropical Tidbits
Friday afternoon and particularly the evening should be the worst of it. Tropical downpours and very strong wind gusts will be occurring. Downed limbs and trees are possible. There does exist the potential for loss of power.
7 am Saturday – Tropical Tidbits
By Saturday morning the storm center has pulled away into Canada and the heaviest of rain has shifted north and east. A trailing shower or two is certainly possible during the day Saturday. Winds will have lightened, but the occasional strong gust can’t be ruled out.
POTENTIAL WIND GUSTS
In addition to the significant amount of rainfall (see below), potentially damaging wind gusts will accompany this system. A very strong low level jet stream will pass overhead (~3,000 ft) Friday afternoon and evening. Winds just above the ground will be greater than hurricane strength. The image below shows one models projection of wind speeds at approximately 3-4K ft above ground level.
Low Level Jet (Friday 1 pm) – Tropical Tidbits
Fortunately, a low level inversion should keep most of the wind above our heads, but some gusts will likely filter down to the surface. Potential wind gusts on the order of 40, 50, even 60 mph are possible as shown in the image below.
Potential Wind Gusts Friday Evening – WeatherBell
RAINFALL
ECMWF Total Precipitation – WeatherBell
In general 2-3″ of rain is expected across the area. Localized amounts of 4-5″ ca’t be ruled out if things line up the right way.
For those of you wondering where the snow is and whether or not we will have a white Christmas the odds are slim. But winter should return for January and an active pattern looks likely.
-Chris
Chris Hampton Weather 