Weather It Is (Winter Storm Warning for Wednesday/Thursday)

 Good Afternoon:

Major Winter Storm to Affect the Country on Wednesday and Thursday.

Our high resolution forecast model shows that rain should transition to snow in the higher elevations of the central and northern mountains, including Jerusalem, Wednesday late afternoon.  Our forecast maps show that snow should accumulate through the night into Thursday morning.  Snow could be heavy at times and strong winds and snow will likely greatly reduce visibility. Many roads will probably be closed.

At the moment, we're forecasting several centimeters of snow generally in the Jerusalem area and between 10 and 20 cm in higher areas within and the mountains just to the north and to the south (Gush Etzion).

The cold weather should persist into Shabbat.

Winds will be very strong, probably greater than 60 km/h during the afternoon and nighttime hours.  These winds could cause damage, so be sure to secure loose objects.

Overall, precipitation amounts Wednesday into Thursday should range from 50 to 75 mm generally from the center of the country to the north, where amounts will approach 100 mm again. Hence, urban flooding is possible, and river and stream flooding is likely from northern Israel to areas south of Mitzpe Ramon, and in the Jordan Valley.

Earlier, there were still some important differences in the positioning of the upper level trough between forecast centers. The NCEP GEFS brings the coldest air into our area, while the ECMWF's forecast model kept the trough a bit further to the north (as it phases with a Black Sea trough).  The latest forecast from the European Center has shifted towards the colder forecasts of the GEFS. How much snow will fall will depend on where we end up in the probability distribution of atmospheric temperatures that make up these global ensemble forecasts, as there is still some variability within them. Still, overall,  they indicate a significant snow event.  Our  high resolution WRF forecast is based on the NCEP GFS, which remains steadfast in bringing a major winter (snowy) storm into our area on Wednesday.

Barry Lynn

Weather It Is (Big Week of Weather)

Shavua Tov:

This weeks looks like our biggest chance for a real snow -- on Thursday and now it turns out Shabbat.

But, first a rainy and possibly mixed rain and snow event on Tuesday, and then the big event to follow.

https://blogs.timesofisrael.com/making-decisions-sometimes-the-right-one/

Weather It Is (Snow Advisory/Extreme Cold)

Good afternoon:

Extremely cold weather is on the way for the next couple of days.  Moreover, next week should see continued unusually cold weather with a good chance of accumulating snow.

Global forecasts show temperatures will soon drop below freezing at 850 mb.  Temperatures will also be unusually cold tonight at 700 mb.  However, relatively warm 500 mb temperatures precludes cooling of the surface layer in the mountain areas through mixing and evaporative cooling, which is usually the mechanism for how temperatures reach freezing or below during snow events.  Hence, during this possible snow event,  any change over to snow will occur simply because the lower atmosphere is chilling to unusually cold levels.

Our latest high resolution WRF ensemble forecasts show that precipitation amounts should be highest over the mountain areas of Jerusalem during the late afternoon and nighttime hour.  This is due to overrunning of moist sea air over cold lower atmospheric air.  This should produce good snowflake growth.  Total amounts of precipitation at the ground are  likely exceeding 25 centimeters.  Some of this precipitation is forecast to (not melt and)  fall as snow, but how much is hard to tell.

These WRF forecasts are based on the Global Ensemble Forecast System, and these are actually running a bit warmer than the European forecast model.  Hence, our forecasts may be underplaying the potential for an accumulating snow tonight.

Based on precipitation amounts, one might expect 10 cm generally to accumulate.  However, surface cooling is the key and this depends on which of the global forecasts verifies. A degree warmer, and just mixed rain and snow.  A degree or so colder, and several centimeters of accumulation in the higher elevations in and around Jerusalem. 

The probability for precipitation is high and the probability for extreme cold is very high.  Will they come together to produce accumulating snow?  Like many things in life, no one really knows, not even your weatherman.

Be well,

Barry Lynn

Weather It Is (Winter Storm Update)

The evening forecast is very similar to the previous forecast. 

The main event will be a period of snow in the Jerusalem area followed by even more extreme cold on Thursday and Friday morning than we just experienced.

Otherwise, periods of rain in the morning into the night over other areas.  Some areas could see 30 to 40 mm during the morning hours, especially in northern areas.

At this time, it's not clear whether there will be a few centimeters or several or even 10.   It will probably depend strongly on elevation.  In any case, the roads will freeze over in the late afternoon and/or evening, so people will be headed home by then.

Have a good night.

Weather It Is (Winter Storm Warning/Extreme Cold)

 Good Morning:

As discussed in our "Israel Winter Weather" group, forecast conditions have trended towards both snow and extreme cold.  In areas that normally see snow during winter storms (including Jerusalem), this combination will create impassable driving conditions late Wednesday into Thursday, if not later where frozen precipitation remains on the roads. Snow accumulations are potentially between 10 and 20 cm in the Jerusalem area, depending on elevation.  Lighter snow amounts are expected in the north.

In our previous storm, the forecast trended away (towards lower probability) as we approached the storm event, leaving us with just extreme cold.  But, we've been watching this potential event for several days, and the trend towards a deeper 500 mb trough, and more prolonged and heavy precipitation has continued to this day (Tuesday).

Some important details: this storm should bring even colder weather than our last.  More importantly, later in the afternoon and evening, high relative humidity in the "Dendritic" zone (-12 to -18 Celsius), will lead to rapid formation of large snowflakes. These snowflakes will form as moisture from the sea overruns the cold air at the surface and within the mountain ridges.  The snow will accumulate quickly, closing roads, so travel will probably be impossible from late afternoon Wednesday into Thursday. The heaviest snow should fall in the late afternoon and evening hours. The deep freeze should last into Friday morning.

Be Safe,

Barry Lynn

Weather It Is (Extreme Cold, Snow?)

 Good morning:

Temperatures on Thursday are forecast to be 2 to 3 degrees Celsius lower than their lows Monday morning.  This means lows around -2 to -4 C in higher locations, or in normally cooler locations in the mountains of Jerusalem and northern mountains.  Coastal areas should be comparatively colder as well, with near freezing temperatures in inland areas.

Currently, the global forecast models GFS and EURO disagree on the type of weather to expect Wednesday.  Both forecast heavy rain as the storm approaches Tuesday night into Wednesday morning. Yet, they differ on the extent of the precipitation and how fast the cold enters our area on Wednesday.  Based on the Euro, there is a likelihood of snow in the central mountains Wednesday afternoon into Wednesday evening, followed by the freeze of Thursday, which should last into Friday.  The GFS predicts less precipitation than the EURO, leaving us just extremely cold.  Tomorrow's forecast  from both models should hopefully indicate better agreement. Incidentally, the EURO was more accurate for our previous storm in terms of the location of the 500 mb trough. It was predicting a more easterly position for the 500 mb trough than the GFS, while now it predicts a more westerly position.

Next week, there is a signal in the global ensembles for a more prolonged storm, possibly snow.

Barry Lynn 

Weather It Is (Extreme Cold and Snow)

 Good afternoon:

The synoptic forcing of rainfall has ended, but not before many places received 100 mm or more.

Now, we're in store for a cold wave, which will probably last into next week, if not the end of next week.

There is some leftover 700 mb moisture, which might lead to light showers and light snow as the cold air rushes in this afternoon. Temperatures should remain near freezing in the highest elevations of the north and central mountains until Tuesday afternoon.  Ice could form on the roads where standing water persists.

Late Wednesday, we're expecting another blast of frigidly cold air that should last until late Friday. There will be a deeper moisture layer with this cold air intrusion, so a period of snow is likely with this event on mountain peaks of the north and the central mountains of Jerusalem.

Next week, another storm is expected.  Current indications are that this storm may bring a more substantial amount of snow, in addition to the unusually cold temperatures.

Barry Lynn

Weather It Is (Extreme Cold)

 Good evening:

As a trough of low pressure dips southward from the polar jet stream, heavy rain should occur on Sunday.

The trough is forecast to move to our east Sunday evening, but as it does it will usher in the coldest air of the season (by far).  

Synoptic forcing for precipitation should be cut off as the trough moves to our east Sunday afternoon.  Normally, this would be the end of the precipitation.  However, the extremely cold air passing over the sea could combine with  lingering moisture in the middle of the atmosphere (at 700 mb) to produce snow squalls later Thursday afternoon and evening (with possible accumulation).  

Temperatures will be close to or below freezing in many locations on Monday and Tuesday mornings.  Similarly cold air should return on Thursday and Friday, and early next week there are stronger indications for our first snowstorm of the year (but the signal for this is just that, and we'll have to see if all the "pieces" fit together (the upper level trough needs to nose down not to our east -- as in the current situation -- but just to our west as the cold air sweeps in at the surface)). 

Cold temperatures are forecast until or through the last week in January.

Shavua Tov,

Barry Lynn

Cold Weather Update

Good Afternoon:

Extreme cold expected.

Most global forecasts indicate that the coldest air will remain to our north this Friday into Saturday, and then extremely cold air on Monday will lack upper level support for more than possible snow showers.  Still, there should be plenty of moisture for heavy rains throughout the period, and snow on the Hermon.

However, there is still a 10% chance of snow in the Jerusalem mountains Friday night into Shabbat morning, and (as noted) extremely cold weather expected on Monday, with widespread frost. Unusually, cold weather is forecast to last until the end of the month.

Otherwise, expect 25 to 50 mm of rain generally, and even some rain over southern areas where flooding can occur.  Locally 75 to 100 mm of precipitation is predicted over central coastal cities from Thursday night into early Monday.

Barry Lynn

Weather It Is (Weekend Storm)

 Good Afternoon:

In the end, the most likely scenario is that the coldest air will remain to our north and east.  In other words, a "bubble" of very cold air no longer is forecast to drift southward towards our area on Friday and Shabbat.  The chance of this happening is less than 10%.  Instead, it will rain generally across the area, except on the Hermon where there will be snow.

The next couple of weeks look to be chilly, with periodic chances of rain, if not snow.

Barry Lynn

Winter Storm Update

The probabilities for an end of the week storm are trending towards 50%, based on the GEFS.  

There is still a lot of potential variability, and it comes down to just how close a cutoff low of Siberian origin (or low extension) makes it this far southward. 

Right now, the GEFS favors a very close track of the storm to the coast of the Mediterranean, rather than a more westerly track discussed yesterday.  The EURO ensembles, which have shown the storm staying to our east, are pushing the trough further to the west than before, but have lower snow chances than the GEFS (about 25%).

Barry

End of the Week Storm

 Good morning:

A very interesting weather scenario is shaping up for the end of the week, Shabbat.  

As pointed out by one of our Israel Winter Weather Group members, Jonathan Hoffman, there is disagreement between the European and American forecasts models, similar to the disagreement prior to our last snowstorm in February 2021.  The European model keeps Siberian cold well to our north and east.  The American model brings the Siberian trough quite far south, in order to interact with a low pressure over the southern Mediterranean.   A more southerly incursion brings a higher probability of snow to our region.

Interestingly, only a few of the GEFS members agree with the Euro, while the rest are some combination of a trough that either heads too far west of us before moving eastward, or moves directly south over our area, bringing snow. 

Last year, the snow "solution" won out.  The next couple of days should clarify our most likely scenario.

Barry Lynn

Weather It Is (Winter Returns and Why)

 Good afternoon:

While it has been periodically and sometimes extremely rainy, my outdoor plants are not sure whether to bust out to spring or hunker down for winter. After all, we had a relatively warm fall and December, and the temperature has rarely reached the low single digits here in the Jerusalem hills. So, why not?

Also, they've heard about global warming and are skeptical that winters in our part of the world just won't be, but will be something they'll tell their kid-seedlings about. 

So, I showed them the charts and maps, and they came away -- even more confused.  Our best guess is that there will be a trend towards much cooler weather after mid-next week and that the cooler, if not colder weather should last into the third, if not the end of the third week of January.  Moreover, we could be moving into the type of weather pattern that brings Siberian cold southward, setting up our first real chance (but just a chance) of snow.  

The reason that the forecast models are confused is because the atmosphere is acting contrary, in a sense, to the typical "La-Nina" Pacific Ocean forcing leads to a pattern of wet/cold and dry/warm locales. Here's a summary from one of our Israel Winter Weather group's Yaakov Consoor, who is a seasonal weather forecaster specialist.

Since late 2020, the ocean temperatures in the equatorial eastern-central Pacific have displayed a La Nina state, meaning water temperatures around 1C cooler than usual.  However, the atmosphere has not always responded in kind.  A La Nina-influenced weather pattern in winter tends to feature a weaker than usual southern (subtropical) jet stream from near Hawaii to the southern US, and from the Middle East to South Asia.  This typically leads to drier conditions across the southern US, South and Southeast Asia, and to some degree across the Middle East as well.  

Meanwhile, an El Nino-influenced weather pattern in winter is typically characterized by a stronger than usual southern jet stream from near Hawaii to the southern US, and from the Middle East to South Asia. This tends to be associated with wetter conditions across the southern US, south and Southeast Asia.  In the Middle East, including Israel, wetter conditions are also characteristic of El Ninos, especially in the past 30 years and especially in the late fall and early winter (Nov and Dec).

The weather pattern has at times between late Oct and Nov, and especially since around Dec 10, turned more El Nino like across the globe with an enhanced Southern jet stream fueling severe flooding events along the West Coast of the US, as well as in Italy, Spain and the Middle East.  Locally, here in Israel, we saw a dramatic turnaround from drought conditions in Oct and most of Nov to a wetter than usual trend that began in Dec, with the Dec 20-23 storm bringing more than 150 mm in large parts of the Sharon, Tel Aviv area, and western Shomron.  

Will the El Nino-like pattern continue the rest of the winter?  Climate models and past experience suggests this is highly unlikely.  A turn toward a more typical La Nina pattern is likely late Jan into Feb.   However, the longer range outlook beyond Jan 20 is still rather uncertain at this point. 

So while we pray the second half of the rainy season will “deliver the goods”, especially in a Shmita (sabbatical) year, the outlook remains rather murky and foggy, as is typical for long range forecasts in Israel.  ארץ אשר יהוה אלהיך דרש אתה תמיד עיני יהוה אלהיך בה מרשית השנה ועד אחרית שנה – Eretz Yisrael  is a land where the eyes of Hashem are always on the Land, from the beginning of the year until the end, so perhaps only G-d knows what we can expect through the rest of the winter.