From the ABC 7 Weather team

Archive for December 2014

Travel Troubles on Christmas Eve as we Heat Up

December 22, 2014 - 03:20 PM
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Winter started officially at 6:03 p.m. EST on Sunday evening. Although it feels like winter on Monday (it doesn’t really look like it out there though with this rain), it is going to feel more like spring as we head into the Christmas holiday. So you might want to trade in the winter weather coat for a spring-like rain jacket and an umbrella for this Christmas Eve.


A deep area of low pressure will push north from the Gulf of Mexico Tuesday night through Wednesday night. This low will travel up the spine of the Appalachian, through the Ohio Valley and into the Great Lakes region. The low will aid in warmer temperatures spreading across the Mid-Atlantic and eventually traveling into the northeast as it pushes a warm front through these areas on Wednesday. This is all ahead of a strong associated cold front that will eventually sweep through early Thursday, taking the rain and the balmy temperatures with it.


A strong southerly wind associated with this low pressure will help push temperatures into the low 60s for Wednesday. Our average temperature for this time of year is in the mid-40s! Temperatures on Christmas Eve area expected to reach at least 15 degrees above normal.

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Since temperatures are so warm, we are only expecting rain across the region-and possibly a lot of it on Wednesday. Precipitable water values are fairly high with this storm, given the time of year. Precipitable water is basically the amount of water contained in a vertical column, just above the surface, if it were all precipitated out—or the available moisture in the atmosphere for generating rain.

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Above graphic shows where we stand as of the morning hours on Monday for precipitable water. It is currently only at 0.38” however, as this system draws moisture in form the Gulf; we are looking at some pretty high precipatable water values well over the 75th percentile.

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This graphic shows large precipatable water values all up and down the east coast on Wednesday afternoon and well over 1.2” in the D.C. region. Therefore, we could get a good dose of rain in spots, especially if we get some heavy bands that set up across the region on Wednesday.


If you are traveling, again, it looks like rain and some gusty winds through the Ohio Valley and to the north. This area of low pressure is not as intense as it has looked in the last couple days but it does intensify well north (through Canada). Therefore, this could limit the development of the low level jet (the low level jet is the flow bringing the deep moisture from the Gulf just above the surface) which in turn may limit rainfall totals up and down the east coast but still will cause some travel headaches.

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Rain will spread across the region for D.C. region Tuesday overnight into Wednesday morning and continue to move northward in New England through the first part of Wednesday. Temperatures from New York to Boston will in the mid-50s to around 60 degrees! Even Maine will be fairly warm with temperatures in the mid-40s! Rain will be heavy and winds gusty at times so I expect there will be some problems if you are traveling north (even though it will just be a plain rain in many locations).

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There will be some snow however, and that will mainly be across Chicago through Indiana and up through Michigan. However, most of these areas will start of as rain with a changeover to snow by Christmas Eve night. There could even be some accumulating snow in the area shaded in blue (mainly a few inches or so and again, that won’t be until Christmas Eve night).


By early Christmas morning, the strong cold front will sweep through the region bringing dry air with it. We will gradually dry out on Thursday getting some sunshine by Thursday afternoon. Winds will be strong on Thursday though, rolling out of the west from 10-20 mph with gusts up to 30+mph. Temperatures on Christmas day will still be a little on the warm side, in the lower to mid-50s! You can see from the graphic below the cold front swinging through on Thursday morning, sliding the warm air off the coast.

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More seasonable temperatures will return on Sunday though after another cold front passes through the area. This could bring some precip for the weekend so make sure to keep an eye on the weather if you are headed home from holiday travel next weekend!

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D.C. Weather Extremes in 2014

December 21, 2014 - 08:52 PM
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The weather pattern through Dec. 31 in the nation’s capital is not favoring any weather extremes that would trump the most notable ones seen so far this year. That said, it was a soggy, stormy and chilly year in Washington.

Here’s a list of the most extreme weather:

What was the hottest day? 99 degrees on July 2nd


What was the coldest high temperature? 21 degrees on Jan. 7


How many 90 degree days did we have? May 13th was the first day at 92 degrees… the last one was Sept. 11th at 91 degrees for a grand yearly total of 24.


What was the coldest low temperature? 6 degrees on Jan. 7th.


When did the highest wind gust occur? 49 mph on May 16 and July 10th.


What single day had the most rain? April 30 with 2.70 inches.


Which month had the most rain? April with 6.47 inches.


When did the biggest snowstorm hit? Feb. 13 with 5.9 inches.


Was precipitation above, at or below average?
Above average. As of Dec. 21, precipitation was 4.15 inches above average.

Were temperatures for the year above, at or below average? So far for 2014, the overall temperature has been near average. The cool months have balanced out the warmer months.

A stormy pattern will bring more rain to Washington next week and a cooler trend will likely arrive to ring in 2015! For more on the forecast, click here.

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A Trip Down Memory Lane- 5 Year Anniversary of December 2009 Snow Storm

December 18, 2014 - 02:44 PM
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The year was 2009. The month was December. Everybody in the D.C. area was gearing up for the holidays. I was at my 1st station in Winchester, VA in the northern Shenandoah Valley as their Chief Meteorologist. I was 4 years out of college and I had a little under 3 years of on-air experience. I saw this storm a-brewin’ about 10 days in advance and remember thinking “if this holds, this could be big.” Well the models kept this storm around and it was looking more and more intense as the date got closer. That date would be Friday December 18th, 2009. That date would also be the beginning of the snowiest winter in Washington D.C.’s recorded history.

 

This storm is classified as a “Miller A” type coastal storm (“Miller” named for James Miller). For this type of storm, an area of low pressure forms along a cold front in the Gulf of Mexico. That low eventually moves off the eastern seaboard and sucks up all the moisture from the Gulf of Mexico. It then continues its trek up the east coast following the jet stream, gathering up moisture and intensifying during its journey.
Everything just came together just right for this storm. It started snowing at Dulles International Airport at 7:30p.m. on Friday. The snow did not stop in our region until 11:00 p.m. Saturday. While I was out in Winchester working a 36 hour stretch while my future colleagues in D.C. were working around the clock forecasting in amazement. I remember telling my production staff snow totals that I was going to have to get on-air with that Thursday. I was forecasting 16.0” – 28.0” for the northern Shenandoah Valley and I had never been more nervous. I couldn’t believe that I was going to have to get on air in my third year of experience and say we are going to get 2 feet of snow….if this didn’t come to fruition, I was surely going to be fired.

As we all know, it did come to fruition (thank goodness) and we received A LOT of snow across the region.

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Wet, heavy snow began to pile up very quickly and cut off many city services. Metro trains stopped running above ground because of the sheer depth of the drifts. I was living in Tyson's Corner at the time commuting to Winchester and driving on 66 on that Saturday was sheer madness. It took me 4.5 hours instead of the usual hour long drive to get from Winchester, VA to Tyson's Corner. A 2 foot wall of snow cut off 66 between Frederick County, VA and Warren County because plows had yet to reach the interstate. Schools shut down leading up to Christmas due to the massive amounts of snow. And as we all know, it only got worse as that winter continued.

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Odds of a White Christmas for Washington D.C.

December 11, 2014 - 02:42 PM
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Are you dreaming of a white Christmas? Okay, let me be honest. After a few days of just a cold rain, I am ready for some snow—and right in time for Christmas. So, what are the chances we can see a white Christmas around the WJLA viewing area?

 

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According to this map put together by the National Climatic Data Center, there is about a 11% -25% chance that there will be at least 1.00” of snow on the ground on December 25th. To break it down, there about a 15% chance of that scenario unfortunately for most of the WJLA viewing area (the data in this map is based on the historic probabilities measured over the last 3 decades from 1981/2010). “This dataset contains daily and monthly normal of temperatures, precipitation, snowfall, heating and cooling degree days, frost/freeze dates and growing degree days calculated from observations at approximately 9,800 station operated by NOAA’s National Weather Service.” (NCDC)

Our local National Weather Service Office has done some incredible research in this category. They found that since 1888, there were only 19 occurrences with measurable snow on the ground already from a previous snow storm OR measurable snow fell on Christmas Day. That on average is about once every 6 or 7 years or 15%.

So you’re telling me we have a chance?! (Inset Dumb and Dumber quote here). Well yes, albeit a small one. The last time we had snow ON Christmas Day was in 2002 when we received a whopping 0.2” at Reagan National Airport. Think about it this way, measurable snow (at least 0.1” of snow) has only fallen on the City of D.C. ON Christmas Day 10 times in the past 130 years. Therefore, on average, snow falls on Christmas Day every 13 years or around 8%.


Check out these stats from the National Weather Service in Sterling (full report here):


“In the past 20 years there have only been two Christmases that had snowfall: 1993 and 2002. Both years featured just a fraction of 1.00”. Furthermore, there were only two years in the past 40 that had 1.00” or more of snow on the ground on Christmas. They were during the very cold December of 1989 when nearly 2.00” f snow was on the ground from previous snowfall that month. More recently in 2009 we had 7.00” still on the ground from the first of our major snowstorms that record setting winter. All 7.00” of that snowpack on Christmas 2009 melted by the next morning (as temperatures rose into the mid-40s).


Of note, 18 years ago in 1993, in a span lasting less than 30 minutes in the evening, 0.2” of snow fell with upwards of 1.00” falling in the western suburbs. That quick bust of snow on Christmas night in 1993 caused severe travel problems. Much of the snow melted on contact with paved surfaces as temperatures were just above freezing at the time the snow feel. However, an arctic cold front swept in just after the snow ended. Any water remaining on roads and sidewalks from melted snow quickly flash froze into a thin layer of ice which caused gridlock and treacherous travel that night.

Precipitation of any sort (rain included) is much easier to come by of course. Fifty-one Christmases have had measurable precipitation. That translates to about a 36% probability of measurable precipitation or roughly on in every three years. “


So with snow falling ON Christmas Day averaging every 13 years and last time we saw snow on Christmas Day was 2002, we may have to wait until 2015 to see some snow fall ON Christmas Day. Usually the typical Christmas Day consists of a morning low of 30 degrees with daytime highs rising into the mid-40s. History also tells us that is it partly cloudy on Christmas Day.

Last year, temperatures were fairly cold in Washington D.C. with some snow flurries on Christmas Eve and as well as the 26th of December. We topped out around the freezing mark (official temperature recorded AT DCA on December 25th was 32 degrees in 2013). Last year was the coldest Christmas since 2004 (high temperature of 31 degrees).

Nothing in the works yet as far as precip or temperatures as we are waaaaaay too far out but as always, we will continue to keep an eye on it as we get closer to the 25th.

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Coastal Storm Brings Wet Weather Beginning Monday Night

December 7, 2014 - 05:58 PM
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It's been a grey start to December, but we finally saw a nice, clear day today.  This was the first fully sunny day since November 21st!  Soak up the sun early tomorrow morning because clouds will quickly thicken, as our next weather system approaches the area.

A developing area of low pressure, off the coast of the Carolinas, will increase cloud cover through the day Monday.  With the clouds, temperatures will only reach the mid 30s by the afternoon.  Here is a look at forecast highs on Monday.

Forecast Highs Monday

Both the morning and evening commutes will be dry, with wet weather from the coastal storm arriving after 8 PM.  Temperatures won't fall much overnight Monday into Tuesday, in fact, temperatures may actually climb a few degrees with an easterly wind component.  Check out our local simulation of radar at 10 PM Monday (1st image below) and 6 AM Tuesday (2nd image).

Local RPM Model Monday 10 PM
Local RPM Model Tuesday 6 AM

This model depicts all rain, which seems to be the trend among most guidance.  As the coastal low tracks farther north Tuesday, there may be a brief transition to snow late Tuesday night well NW of D.C.  Little to no accumulation is expected.  In fact, by Tuesday at 8 PM the coastal storm will be greatly impacting New England.  Here is a simulation of the coastal storm at 8 PM Tuesday.

Surface Features Tuesday at 8 PM

This will be a predominately rain event for us with the greatest snow potential over interior New England.  Check out forecast snowfall accumulations by Thursday afternoon.  Areas shaded in pink could receive over 10" of snow.

WxBell GFS Forecast Snow Total By Midday Thursday

The area of low pressure will get cut-off from the jet stream midweek and will spin freely over New England through at least Thursday.  That means added clouds for us Wednesday and Thursday with possible light rain and snow showers. 

There are still uncertainties to the forecast, since the coastal storm has yet to develop.  The Stormwatch weather team will continue to update the forecast, as new information becomes available. 

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More unsettled weather for the weekend ahead

December 3, 2014 - 05:34 PM
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The pattern doesn't appear like it will change anytime soon after bringing nearly an inch of rain to parts of the region Monday night into Tuesday and clouds on Wednesday. Thursday should experience a lull in the action, just in time for the National Christmas Tree Lighting, which Chief Meteorologist Doug Hill will be out live broadcasting tomorrow evening.

At this point we are expecting some sunshine in the morning hours followed by afternoon clouds as the next system pushes in from the west. A few models have depicted the chance for a few showers late tomorrow night into Friday morning, but this should be a low probability at this point with the best chance south and west of D.C.

Water Vapor image with tomorrow's disturbance and Saturday's disturbance

Looking west, an area of low pressure has been bringing inches of rain to parts of California over the past few days. A bit of energy and associated moisture has spun off this system and will help bring clouds to our region Thursday afternoon through Friday night.

Thursday rainfall totals as of 5pm for parts of California

Another area of energy will push into Southern California tonight into Thursday morning. This disturbance will move across the U.S. and into the Mid Atlantic this weekend, increasing chances for rain Friday night into the day Saturday.

Precipitation forecast for Friday through Saturday evening

Beyond Saturday, there are stark differences in model depictions, with a few models spinning up additional areas of low pressure off the east coast and socking the region in clouds and precipitation Sunday and Monday, and another completely clearing the region out Sunday with sunshine and mild temperatures. We will get a much better handle on this forecast in the next 12-24 hours but at this point are content on keeping the rain chances in for Sunday and again Monday.

Forecast precipitation Saturday through Monday Evening

 

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Winter Weather Advisory for parts of the D.C. area Tuesday

December 1, 2014 - 03:27 PM
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A cold front will sweep through the region on Monday afternoon/evening. Temperatures will fall behind the front, eventually ending up in the 30s for overnight lows!

Cold front will move through Monday afternoon/evening bringing a threat of isolated showers and dropping temperatures.


Eventually that front will stall just to the south of the region. An area of low pressure will ride along the front Monday night into Tuesday bringing precip with it. At the same time, high pressure will move front the Great Lakes region to the New England area. Eventually this evening, our winds will shift to the north and east bringing moisture and cooler air off the Atlantic Ocean and right into our area. What happens is, that moisture banks up against the mountains to our west creating a “cold air damming” affect or CAD. This set up generally makes forecasting that much more difficult, especially when determining precipitation types because that colder air will slide right under the warm air aloft which would make the precip type more of that of a wintry mix (freezing rain/sleet).

Winter Weather Advisory from 1am Tuesday to 1am Wednesday

Just around daybreak and into the morning commute, we will start to experience some spotty sleet and freezing rain, mainly north and west of D.C. (Loudoun County and Central and Western Montgomery County and points northwest). Inside the beltway, along I-95 and areas to the south and east, this event mainly looks like a very cold rain event but I can’t rule out some isolated pockets around D.C. of the wintry mix.

This is NOT looking like a major event but since it comes for the morning rush, there could be some problems (as there tends to be, even if it is just plain rain). And we are really not expecting that much to accumulate at all, perhaps just a glaze in some areas. Surface road temperatures, especially around the D.C. area, are above freezing so just like last Wednesday, any frozen precip that falls will have a hard time sticking. However, north and west of town on some rural roads, elevated surfaces (bridges and overpasses) and even exits could have some slick spots.

In-house model of Tuesday morning (rain = green, wintry mix = pink)


Again, I do not think this is going to be a huge event but I don’t want it to take anybody by surprise when our temperatures do not make it out of the 30s tomorrow (considering we are around 70 in a lot of the area on Monday).

Warm air will start to erode the shallow layer of cold air and any wintry mix will turn to plain rain by the afternoon hours. Most of the precipitation should move north around the kickoff of the evening commute but I do expect there to be some drizzle and fog around the region – there could even be some freezing drizzle at the high elevations). Temperatures rebound into the lower 50s on Wednesday but another bout of precipitation could be on the horizon for Friday.

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