Category Archives: Weather Outlook

WEEKEND WEATHER OUTLOOK

More storms and very cold weather on the way

Forecast Update Thurs 10:25 PM— Tonight’s models are suggesting that light mixed precipitation may start Saturday afternoon.


Earlier this week it became clear that an imminent plunge in cold air from Canada would be the ingredient for stormy winter weather here.

Monday’s GEFS Temperature forecast for Sunday

 

Today’s (Thursday’s) GEFS forecast for Monday morning.  Temperatures will be in the minus 30s in the Midwest.  (temperatures, not wind chills!) (Click on image for a larger view.)

 

Monday’s forecast for three storms hasn’t played out as expected— the plunge and amplification of the jet isn’t exactly what was forecast.  The cold air is deeper than forecast in the Midwest and moving more south than southeast.  

We had the first snow last night.   Tonight into Friday’s storm will move south of us, missing us giving us a rest.

Saturday will be mostly cloudy and continued cold.

The next storm will affect us on Saturday night through Sunday. Right now, a light, mixed (sleet-freezing rain-rain) precipitation event is what is forecast with the main system moving to our south. 

GEFS Sunday 1 PM Precipitation Type (PTYPE) forecast  (Click on image for a larger view.)

 

We’ll have mostly sleet and some snow with this Saturday through Sunday system as warm air is expected to move in from the Atlantic.  On Sunday, we may have our high temperature for the entire next week of about 37º!  It would not take much for this forecast to change in to either a snow storm or a miss.   But the models are in general agreement that it’s going to be a sleet mix with little accumulation.

The next significant storm is expected Monday night into Tuesday.  This may give us 4-6 inches of snow. Of course, it’s way too early to predict accumulation.

Following the Tuesday storm, temperatures will get into the single digits at night. 

Stay tuned for further updates..

JUST A SNOW POSSIBILITY

Fri 07:37 AM Update — The next chance of snow for us (Monday evening into Tuesday) is about 96-108 hours in the future, still beyond the range of the short range, higher resolution  models.  (The shorter range, higher resolution models forecast 84-89 hours in advance at best. Many only forecast 48-60 hours in advance.)  

Current operational GFS snow totals by Tuesday afternoon—

GFS snow totals by Tuesday afternoon. (Click on image for a larger view.)

The above GFS snow totals are somewhat similar to the ECMWF (European), Canadian GEM-Gobal and German ICON.  Stay tuned.

Thank you to those of you who took part in my recent user feedback poll.  Here are the final results:

“Users, would you like  to see all  updates posted to Twitter or just the major new posts (as currently done)? “

With it so close, I’m going to stay with only posting major new posts to Twitter,  but with an occasional update also posting. (A slight change to the  current approach I use.)   The updates (such as those on this page) won’t be automatically posted to Twitter.

Thu 08:06 PM Update — Today’s GFS has joined other models (Canadian, European, ICON and GEFS)  in predicting about 1-3 inches of snow here Monday night into Tuesday morning. (Unfortunately, the newer GFS v16 has not been available today due to planned maintenance of NOAA’s servers.)

Current GFS snow totals for Tuesday 10 AM  (Click on image for a larger view.)

 

A new wrinkle for getting larger snow accumulation is going to be temperatures, which are trending somewhat warmer at certain levels of the atmosphere, especially near Philadelphia.  Many areas will have a sleet/rain mix at times during the event reducing snow totals and making an accurate snow total forecast difficult.   Since the storm is coming during the nighttime hours, a period of sleet or freezing rain is a possibility as temperatures near the ground may drop below freezing—

GFS Precipitation Type (PTYPE) Monday evening (Click on image for a larger view.)

A change back to snow is expected before ending Tuesday morning.

The fine structure of the thermal profile won’t be known until the day before the event.    Stay tuned.

 

From Wednesday …

Today, several people at work asked me, ‘so where’s the snow?’

The statistical ensemble (GEFS) model continues to forecast a minor snow possibility for the overnight period from Monday into Tuesday morning.  (see yesterday’s post for the precip forecast graphic; it hasn’t changed much with today’s model runs.)

The sort of thing I like to do is compare the soon-to-be-released GFS model version 16 and the current operational GFS model (version 15.2)’

(The GFS 16 is scheduled to become the operational model the first week in February.)

The soon-to-be-released GFS 16 has  significant snowfall for our area, 4-7 inches—

GFS v 16 precip rate forecast for Tuesday 7 AM   (Click on image for a larger view.)

 

The current operational GFS model has the storm a bust with little development and little snow—

GFS (current operational) forecast Tuesday 7 AM (Click on image for a larger view.)

 

The current Canadian Global and the European models are closer to the the low end with some snow 1-2 inches.

In the time period in question (~138 hours in the future), the statistical GEFS model is probably the one to consider most—

GEFS snow totals Tuesday morning  (Click on image for a larger view.)

 

If that’s the case, the soon-to-be-released GFS model v16 has a serious precipitation over-prediction bias. 

The fun of this is to see what happens.   Stay tuned.

 

REALLY QUIET WEATHER-WISE

Tue 11:15 PM Update — Some of tonight’s models are showing a coating to about 1/2 inches of snow with snow showers described below.

This seems to be one of the dullest winter weather periods in recent years.  As shown in last Friday’s forecast and graphic, the jet flow is flat due to cold air that doesn’t seem to want to make its plunge into the US. 

For some time, the weather models haven’t shown any storm on the horizon for us, in contrast to last winter season, when the models showed numerous storms  (but they were usually false alarms).

Nonetheless, an upper trough will swing through early tomorrow (Wednesday) morning.  A strong area of vorticity is expected to pass through our area about 6-9 AM Wednesday.  There will be enough moisture for snow flurries or snow showers around daybreak Wednesday morning and it will become quite windy after it moves through—

NAM model vorticity 8 AM Wednesday  (Click on image for a larger view.)

While there are no major storms on the immediate horizon, over the past several days, the statistical ensemble GEFS model has been showing a low pressure system moving by next Monday into Tuesday morning with maybe an inch of snow for us—

GEFS model forecast for Tuesday Jan 26th.   (Click on image for a larger view.)

The models don’t show any coastal development of this low at this time. In the weather world, next Tuesday is a long ways off in the future.

Next week is also looking somewhat colder here and cold air is definitely building in Canada.    Stay tuned.

 

SO WHERE’S THE SNOW?

I should preface this post by saying that I enjoy trying to predict snow rather than dealing with it after it has fallen. Pretty when it falls, a pain afterwards.

That said, I’m being asked, ‘ so where’s the snow?’

I’ve mentioned since the end of November that my sense of the weather pattern so far this winter is what I like to call “a lack of very cold air” to our north.

Here’s the current GFS statistical ensemble forecast (GEFS average) expected minimum temperatures for next week—

GEFS statistical average minimum temperature forecast for next Friday.  (Click on image for a larger view.)

Well, maybe you’re thinking, -24ºF seems awfully cold to me? The truth is, when things get going, temperatures are as low as -40º to -50º in the same areas above, especially in Greenland. (Greenland is looking awfully warm this year.)

Contrary to what many weather entertainers on TV seem to suggest, the jet stream doesn’t just do it’s own, arbitrary thing. The jet stream, a fast flow of winds at about 35,000 to 40,000 feet in winter, is a river of air actually flowing in the three dimensional “valley” between air masses.

It is the density and shape of the cold air mass that determines the shape of the valley and of the jet, not the other way around. In essence, the jet flow shape in winter depends on the “sag” of very cold moving southward, as depicted below with the white line—

GEFS forecast Jet Flow (300 mb winds) next Friday (Click on image for a larger view.)


Notice that the white line is tilted slightly eastward instead of straight southward.  The relatively “not so cold air” up north doesn’t have the mass density to dive straight south.     The jet stream flow (red arrows) isn’t suppressed directly southward, but rather southeastward.  

There also hasn’t been much of a blocking effect of a large cold air mass over Greenland and the Northern Atlantic to cause the same jet flow to bend back north up the coastline. 

As a result the two “jet streak” impulses (numbers 1 and 2 above) develop low pressure systems, but these move out to sea.  

So we need colder air in Canada, and colder air in Greenland and the North Atlantic.

The time period depicted above (January 15th-20th)  does show some positive trends towards snow here:

  • Temperatures are colder in Canada than they’ve been.
  • The jet flow next week will be “less split” than it’s been.   It does appear that some phasing may occur between the northern jet flow shown (disturbance #1 above) and the southern jet flow (just visible on the map from Mexico and near #1)

So, some colder temperatures and some action is possible January 15th – January 20th, although not currently captured on the models.  Stay tuned

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FORECAST OUTLOOK- THIS WEEK AND BEYOND

The current weather pattern forecast by all models, is for the jet wind flow to broadly stay far south of our area,  preventing any disturbances from moving up the coast and keeping them moving out to sea.

Current model forecast for Sunday, showing jet stream wind flow (Click on image for a larger view.)

Several disturbances moving into the Pacific northwest US will follow this path. (The northern jet flow is so far north, it doesn’t show in this map!) Until things change, expect near seasonable temperatures and no snowstorms in our neck of the woods.

The medium and extended range models maintain this general pattern for the first two weeks of January. A change in the pattern may occur sometime around the 15th to the 20th of the month, when an arctic outbreak may shake things up. Of course, things can always change sooner, but this is the current model outlook.

User Feedback Requested: 
Users, would you like  to see all  updates posted to Twitter or just the major new posts (as currently done)?   Thanks!

This poll is no longer accepting votes

Your Feedback Requested Always Post to Twitter?

This survey expires on 1/20/21