Watching the southern storm track

The mild stretch is at an end.. and temperatures look to return to seasonal averages through Christmas week. No extreme cold looks to be on the table through Christmas.  Southern reaches of the district will be close enough to an active southern storm track to be on the lookout for at least some snow potential, while unless things change, the west and north sit on the sidelines with a quieter and drier pattern.

Outlook:

Through Thursday…Back to reality for mid December with near average temperatures. Lows in the 20s and highs mid 30s to around 40. There may be a few light showers or flurries Wednesday night or Thursday, but deep moisture will be lacking and higher resolution computer guidance continues to be unimpressed by this weak system aloft. We’ll have more on this system tomorrow.

Friday-Sunday…Attention turns to next Pacific storm. Many questions remain but it is looking more of a weather maker for southern areas vs. the north. Periods of clouds with some flurries for areas from mid Missouri west with some snow chances from STL south and east. Continued near average with 30s for highs and 20s for lows.

Christmas Week.. Southern jet stream/storm track remains active and we’ll have to watch the next system expected to reach the west coast this weekend. Current indications are it will be weaker and may take a path even further south than this weekend’s system, potentially bypassing the area.  Plenty of room for change, however and the overall pattern does bear watching closely.  What can be said is that we anticipate near average temperatures to continue..no extreme cold or extreme warmth. Highs in the 30s and lows in the 20s look likely.

Over the weekend we had a mild and wet weather system move through.  It wound up across Kansas on Sunday and then tracked to northwest of KC and into Iowa this morning. A band of rain and a few thunderstorms tracked well out in advance of the low pressure area’s frontal systems.  That rain reached KC mid to late evening Sunday and SEMO/SW IL/STL this morning.  Rainfall was modest and as was predicted, heaviest west (3/4″ to 1″+) and lighter east (1/10″ to 1/2″).  Here is a graphic estimation of the rain totals, in the image dark to light blues are totals around 1/3″ or less, blues and greens are 1/3″ to 3/4″ while yellow-green to yellow are totals 3/4″ to 1″+.

2014-12-15-1106-EDDOBSQPF

As was mentioned yesterday, these totals will only add to the yearly surplus for KC & STL while make up a little of the deficit for SEMO/SW IL. This most recent rain comes around 10 days after our last significant rain event.

Here is a look at the departing storm on this afternoon’s satellite image.

2014-12-15-1407-SATSFCRAD

We’re halfway through December today and it’s been snow-free to date for many, not only here but around our region as a whole. December has had no snow recorded in Kansas City with 1/10th of an inch in St. Louis.  The season total stands at 3.9″ for STL which would be #4 on the list of top ten least snowiest winters if no snow fell the rest of winter.  Kansas City’s season total is even less– just 1/2″ and would be the least snowiest winter on record if no snow fell the rest of winter. This is not likely to happen however.  Typically 4-5″ of snow fall in December across our area. It is not uncommon for December to lack significant snow.

2014-12-15-1118-SEASNWALL

This weekend, significant snows returned to the northern Plains with Nebraska and South Dakota seeing accumulating snow, which spread into Minnesota.

The lack of snow has been due in part to a pattern which has produced a lack of Arctic air.  As of this morning, a glance at the surface temperatures in the Arctic show that brutal cold continues in eastern Asia.  Temperatures of -40 to -60F are concentrated over eastern Siberia, with subzero readings crossing Alaska’s North Slope and settling over the Canadian Arctic and Greenland.  Readings are (relatively) mild over NW Canada with temperatures above zero.  Much of northeast Europe is also mild.

2014-12-15-1017-12ZGFS2MT

The pattern this month has featured a stable situation over the Arctic, where we see a strong jet stream “containing” the Arctic air.  Bitter cold continues to recirculate from the Canadian high Arctic and Greenland across the pole into eastern Russia.  There’s no easy path for the cold to build south into North America.  Mild Pacific air has flooded NW Canada.  The polar regions see little to no daylight this time of year and the 24 hour night allows temperatures to continually chill over the snow and ice pack.

2014-12-15-1017-12ZGFSH50

There are indications that this pattern will begin to change Christmas week. More on that at the end of the blog.

Possible late week winter system:

There has been a lot of disagreement with regards to a weather system expected to impact parts of the district this weekend.  The issue the guidance is having revolves around an upper low over SE Canada.  That low’s movement will determine how the next weather system tracks.  The more reliable guidance suggests this low will be stronger and slower to leave–blocked by a ridge of high pressure to it’s north (the warm tones from Hudson’s Bay to the north Atlantic).  This means that our next system is also blocked from tracking northward and instead will track more eastward across our part of the country.   For us, a southern track means a greater risk of wintry weather for SEMO/SW IL and a lesser risk for the I-70 corridor.  Exactly how much that Canadian low weakens/moves will modulate the storm track for our area. Stronger/slower means that the storm takes on a further south path-bringing wintry weather to the mid south/TN/OH valley.  If the Canadian upper low is weaker and faster to move out that would allow our storm to shift more north and west as it crosses our region, bringing winter weather further north and west.

2014-12-15-0934-ECM500108

While no solution can be ruled out at this point — it can be said with fair and increasing confidence that KC will miss this system. No operational and very few ensemble models bring the track that far north. The STL area is in a more uncertain area while SEMO/SW IL will need to carefully watch how this evolves in the next 24-48 hours.  It should be noted that just-arriving in data is certainly less bullish when it comes to winter weather-even for SEMO/SW IL. Lets take a look at what the operational models show. Pictured below are model snow forecasts through 6AM Sunday from the Euro, Canadian, GFS Experimental and GFS. (Click to make more readable).

2014-12-15-1320-ECMSNW144 2014-12-15-1320-GEMSNW144 2014-12-15-1320-GFSSNW144 2014-12-15-1320-GFXSNW144

We’ve broken down the areas to pinpoint accumulations that fall today (purple), midweek (yellow) and next weekend (green).

For comparison, look at the Euro 24 hours ago (L) compared with today (R). That’s quite a change in 24 hours!  Big changes in the model are bad for forecast confidence. When that happens, we have to look more in depth.

2014-12-14-1120-12ZECMSNW 2014-12-15-1320-ECMSNW144

We’ll look to the ensembles. In addition to the deterministic –or official run– of each computer model, there are 51 different “versions” (called members) of that run and one control version of this model. They are all run using the same data at start time but are each run with slightly different equations. Doing this yields an average of all the versions in addition to the official version. The average still focus on SEMO/SW IL.

2014-12-15-1417-12ZEPSSNC

Today’s “control” run (L) is more similar to yesterday’s operational run (R):

2014-12-15-1417-12ZEPSSNT2014-12-14-1120-12ZECMSNW

Take a look at how the different members all play out snowfall accumulations through Sunday morning.  Notice 24 of 51 bring at least 5″ of snow to SEMO/SW IL.  13/51 bring 5″ to STL. Only 2 of 51 bring 5″ of snow to KC. That’s why along with the operational models, we can begin to eliminate KC from the area of concern, but not STL. SEMO/SW IL still need to watch this system even though the operational models are just recently not all that impressed.

Group 1:

2014-12-15-1417-12ZEPSSN1

Group2:

2014-12-15-1417-12ZEPSSN2

As always, a real problem with potential storms this time of year is that we, and in turn, computer model guidance, does not get a good view of the storm until it reaches the coast.  Now, it is well off the coast and all the information the models get about the storm is from satellite sensors or very few ship reports.  This kind of gives only a “2-D” image.  Once the storm enters the upper air network, weather balloons sample the storm with much more depth and detail “3-D” if you will.  The storm should be sampled as it reaches the coast Wednesday and we’ll be able to see clearer trends on how it will interact with the Canadian upper low.

2014-12-15-1215-EDDSATGLB

The overall summary still pretty well agrees with this map, posted this morning. Right now the areas that need to most closely watch this next system are mainly SE of STL. As was stated this morning, this is nothing to worry about at this point- just a POSSIBILITY to be aware of.

2014-12-15-0837-WXIWSWGEN

By the time it reaches the eastern seaboard, that low is expected to have moved/weakened and that may allow our storm to become yet another nor’easter.

Finally, the signs are there for a return to the cold reminiscent of last winter and this November by month’s end.  Take a look at these Arctic mid level charts.  The one on the L is from earlier in the blog.  The one on the R is for December 30th.  Note on the L image how the blue colors are concentrated near the pole.  That’s a stronger polar jet helping to contain the cold.  On the R, look how the blues have split into differing areas, with one notable low in the Canadian Artic.  Also, the return of the Alaskan ridge and another ridge near Greenland.  This type of flow becomes cross-polar and able to deliver the chill from Siberia across the pole and southward once again.

2014-12-15-1017-12ZGFSH502014-12-15-1507-12ZEPS348

The same times, but a wider view:

2014-12-15-1508-12ZEPS000 2014-12-15-1508-12ZEPS348

Timing the transition will be an issue, but January may be a lot more like November, rather than December.

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