VA WEEKEND WEATHER JULY 2-3-4-5 and JULY 9-10-11

Posted by wxrisk | GENERAL | Wednesday 30 June 2010 11:01 am

1100 EDT    JUNE  28  

This updated Forecast discussion is now being placed in the GENERAL weather section in addition to the Virginia weather section because the threat for MAJOR …possibly even a historic Heat Wave for the Middle Atlantic region is increasing. It also appears to be spreading into the lower portions of the Ohio Valley— aka the southern ECB – the Tennessee Valley and the Deep South.

Surprisingly the THREAT or the potential for seeing this sort of serious heat for several days in these areas is getting very little attention. I am afraid that is because there seems to be an over emphasis on the GFS and the GFS ensemble. This makes it less sense when one considers the unbelievabley BAD models performance by the operational GFS and the GFS ensemble with regard to hurricane Alex.

As we can see from this particular Image of the 6/30 run of 0z GFS for JULY 6-7-8 … The model that keeps the trough over the plains states moving straight through the Midwest. This ensures that there is no significant ridge in or dome that forms over the eastern Conus in any way shape or form.    Really this is a CHICKEN vs EGG question. If we had a strong ridge over the eastern Conus the trough to slow down.. and temps would soar.

Here is the 0z  6/30   run of   the  operational European model from early this morning .    At 500 MB we can clearly see the model continuing to form a very strong dome over the Middle Atlantic states and the Dark red shading shows 850 temperatures of +24c to +27c… which translates at the surface to temperatures well above 100°. Keep in Mind that here in Central Virginia we have already several days with temperatures above 100°.

These maps in ages shows the forecasted Max temperatures for our day afternoon of July 5 July 6 July 7 July 8 and July 9. The band of 100 plus degree temperatures is quite impressive and as you can see that there are two large areas of 105-110° over a portion of the commonwealth on July 6 and over VA into North central NC and over western TN and southeast MO on July 7.

Just in case you were wondering the record high temperature for the month of July in the city of Richmond is 105° which was set back on July 6, 1977.



1100   EDT   JUNE  28

Now that I taken a week off because of my summer vacation … it is now s time to go back to work and figure out the weekend SUMMER forecasts for the commonwealth. Today will probably be the third day in the last five or temperatures reached over 100°here in Central Virginia. The cold front which is going to ride on the 30th will certainly be a welcome relief and it will ensure that the upcoming July 4 weekend will be spectacular. Friday, July 2 and Saturday, July 3 will feature and seasonal temperatures with low humidities an absolutely no friend of any sort of rain whatsoever.

Temperatures will begin to warm up of course by July 4 but this will be a great weekend so you should get out and enjoy it if you can.

However, that a weekend where facing a very interesting meteorological dilemma because the European and the gfs weather models are forecasting very different scenario as for the entire eastern Conus …. In the Middle Atlantic region …. For the period from July 5 to July 9.

Both weather models move the deep trough over the east coast out into the western Atlantic by July 4. This forces the large cool area of high pressure over the eastern Conus to move off the coast as well. In response for the trough moving off the east coast the strong ridge over the Rockies and the Plains rapidly expands the east.

The European models developing a heat dome over the eastern third of the Conus. The GFS does not.

Both models agree that another major trough will come out of Western Canada and the Pacific Northwest during the July 4 weekend which will track through the northern Rockies and into the Upper Plains by July 4. This front will undoubtedly bring widespread significant rain to the the Plains and the Upper Mississippi valley and some of the ramains /moisture of Alex will undoubtedly get pulled into the cold front so the rainfall amounts over the central Plains & the Mississippi Valley could be impressive.

The 0z Monday 6/28 run of the GFS moving right through the Midwest because the the model has no ridging or dome forming over the east coast . The Euro shows and a massive heat wave developing with temperatures rising above 100°over much of the Middle Atlantic states including the big cities of the northeast with the heat expanding into the Ohio Valley the Tennessee Valley into the Carolinas and the Deep South .

They will be interesting to follow this and see which of these very different solutions will be correct.


VA WEEKEND WEATHER JUNE 18-19-20 & JUNE 25-26-27

Posted by wxrisk | GENERAL | Wednesday 16 June 2010 11:48 am


1100  JUNE 16

There is not really much to change in this forecast for this coming weekend  JUNE   18-19-20   as all the data shows is gonna be a beastly hot weekend for the middle of june across the Middle Atlantic states. The driving mechanism here has to do with the overall pattern– which features a strong ridge over the eastern Conus and the deep trough over the West Coast.  These two features are in a symbiotic relationship with each other– which of the weather business is known as a Teleconnection.   The deep trough on the West Coast forces the atmosphere to respond by developing a strong ridge downstream which in this case happens to be over the Deep South.  This is exactly what I thought was going to happen for the summer pattern and so far it appears to be developing quite nicely.

Synoptically the key feature is going to be the major system which is going to move through North Dakota and southern Manitoba on Thursday.  This Low’s associated cold front will move into the Upper Plains and the Great Lakes area this weekend and early next week whereupon the cold front will stall.   These areas will probably see the numerous heavy thunderstorm clusters developing over the next 5 days.

However this front will not reach any portion of the northeast.   Indeed the actual low pressure area track through Ontario then into central Quebec and this will will serve to reinforce the ridge over the eastern Conus. As a result temperatures will increase dramatically this weekend over all of the Middle Atlantic with W or SW winds and strong High pressure off the se coast I would not be surprised to see temperatures break 100°over much of the commonwealth on Sunday.

Areas just to the north however will be substantially cooler… And once you get north of say interstate 80 in Northern Pennsylvania Northeast New Jersey and New York City temperatures will be only around 90°.

Coming out of the weekend the models continue to show that a dome is going to form that will be imbedded in the large ridge across the lower plains and the Deep South. The European model is more bullish with this dome and stronger then the GFS. The effect for VA weather will be to keep temperatures at least in the middle 90s for a good portion of the commonwealth from June 21-24.

WEEKEND #2   JUNE 25-26-27…

Not surprisingly the 0Z and 6z GFS want to bring a fairly strong trough and surface cold front thru the Middle Atlantic and the New England states during this weekend which would provide for cooler temperatures and some showers and thunderstorms.

However the European as well as the GFS ensemble does not support that idea .  These models show a much shallower trough but only moves through the Great Lakes and New England and has no real impact over the Middle Atlantic states. As a result of looks like the last weekend of june could be another rather very hot weekend.

It is probable that for the Rest of the Summer 2010 forecasters will be dealing with the strong Ridge over the Lower Plains and Deep South.  It will be the movement of this Ridge that will be the determining factor of How hot VA gets and for how long.


Not only have we moved into the beginning of meteorological Summer but the overall atmosphere pattern clearly supports a True Summer and NOT Spring like pattern.

The current pattern continues to feature a persistent trough in the jet stream over the Pacific Northwest and the northern Rockies.  At times the trough extends into the central Rockies where the Great Basin.   To counter this persistent trough the atmosphere develops a ridge over the southeastern US.    At times the ridge extends into into the Southwest states and the Lower Plains.

We can see this very clearly on the 0z Monday European map for early Monday morning.   

By Day7 not much has changed… The trough remains persistent over the Pacific Northwest and the northern Rockies… and the Ridge remains strong over the Deep South. And by Day 10… very little has changed. In fact the model shows a dome developing over the Deep South that is embedded in the ridge. 850 mb temperatures surge to +24c which equates to service temperatures in the middle or upper 90s. As you can see from this map those sorts of temperatures do reach into central and Southern Virginia.








JUNE 18-19-20.

 of the three days and Friday will be the coolest and less Humid as High pressure and over the Ohio Valley moves into the Northeast.  This High will not be very strong and l move off the coast for the weekend which means winds will become SW and the heat & humidity will build.  Most of the commonwealth should see temperatures in the middle 90s on the 19th and 20th.

There will be a cold front that tries to move through late on the 20th or early in the 21st.  At this Point I don’t know if this front will have enough push behind so that it reaches into the commonwealth or what sort of thunderstorm activity if any this front might have.

WEEK 2 JUNE 25 – 26 – 27:

The 0Z European ensemble data remains quite impressive. It shows a very strong ridge centered over the Ohio Valley. The 0z GFS ensemble is NOT as Bullsih with this Dome idea but the 0z GFS ensemble still shows a strong Ridge in place over most of the Deep South which means above normal temperatures… Even by the standards of late JUNE.


Posted by wxrisk | GENERAL | Wednesday 2 June 2010 11:06 am

1100  JUNE  2

The model data continues to shift here as we go through the middle portion of a week.   Earlier it looked like a major trough was going to move through the Midwest and the northeast this weekend– mainly on Sunday June 6 and Monday June 7.  But each subsequent run of the various models — such as the GFS Euro and CMC– is showing that this trough is weaker because the energy coming in from the Pacific is so strong that the trough is really is not getting a chance to amplify as it moves through the Great Lakes and the Northeast.  It looks like a pretty good cold front for the Great Lakes and from Pennsylvania northward into New England on June 6-7 .  But as things  stand right now for the Lower Middle Atlantic states this cold front may not get far enough south to bring about any sort of significant shower thunderstorm activity  SUNDAY   June  7.

Coming out of the weekend the forecast is going to get complicated.

The model data shows that of the strong ridge over the southwest states will attempt a slide into the Lower Plains and the Delta region for several days starting on June 5… nad lasting through June 8.

Indeed the model data from the European and the GFS shows temperatures greater than 100°… and in some locations as high as 105° over large portions of eastern NM TX OK A and M- U 90s into southern half of COL KS ARK and LA.

Typically when you get a ridge like this forming over the Lower Plains as it comes out of the southwest states… the ridge likes to build north and east into the central Plains and the Midwest.   But in this particular situation the very strong Pacific jet stream will be racing across the top of the ridge essentially in a west east direction through the Central Plains the Midwest and into the northeast all next week.

This does TWO things… FIRST this sort of strong active Pacific jet stream ensures that the heat over the lower plains will not get any further north then say interstate 70. Second this sort of strong flow becomes DIFFLUENT aloft on the synoptic scale.   In other words pieces of energy moving in the jet stream (vot maxes) will cause thunderstorm development and thunderstorm clusters to form over the central Plains and the Midwest… and possibly into the Middle Atlantic region.

JUNE 11-12-13

As we approach the second weekend JUNE 11-12-13… Which in turn will allow for the strong ridge over the southwest states to begin to slide or expand eastward.  Without the trough lingering over the northeast the ridge will have a much better chance to expand into the central plains and the Midwest .  This could be the beginning of the first significant hot. For most of the Midwest the Deep South the Tenn valley and the Middle Atlantic region.  The euro and GFS ensemble data is quite impressive here showing the ridge to the setting up over the these areas whiile on the West Coast the trough stays put.

The West coast trough the serving as an anchor in the overall pattern because as long as the trough stays strong and deep over the west coast / Pacific NW the Ridge stays strong and Deep over the Plains and Midwest and East Coast.


1200 EDT   MAY 31

Although most of the commonwealth has not seen significant showers and thunderstorms over this long weekend there have been a few areas which are been hit pretty hard. Here in downtown Chester– mind you there is no such place as downtown Chester it’s just sort of a phrase I use– we been hit with two significant thunderstorms and the last three days– one during the early morning hours of Friday 1-2am — and again Saturday evening when a series of storms cells kept “popping ” up over the region.

And judging by the Monday afternoon radar looks like we will probably see some more storms later on this afternoon and on Tuesday.

 JUNE  4-5-6

Last week many of the weather models are showing a pretty strong cold front associate with a fairly strong upper trough moving through the Midwest and the northeast JUNE 3-4.  That still appears to be the case to the model data here on the 0z and 12 runs Monday appeared to be somewhat weaker with this front.  This means that Friday, June 4 is likely be a fairly stormy start to the weekend especially in the afternoon in the evening.  At this point most of the model data is driving the frontal off the coast which should mean that June 5 and June 6 would be decent days with less humidity somewhat cooler temperatures and dry conditions.

However the European and the GFS models here at midday are showing a bit of a change.  Theese models   take of the next big shortwave in the jet stream across the Upper Plains and moving through the Great Lakes where surface Low pressure develops. The Low tracks ENE thru the Great Lakes into New York State Sunday, June 6 then up into Maine on June 7. Normally this sort track is not a big thunderstorms threat for the Middle Atlantic region and especially for Virginia.

But because of the shape or configuration of the jet stream…  (the 0z GFS and euro show a very diffulent aloft jet stream pattern)…   the thunderstorm potential for Sunday afternoon June 6 over the commonwealth appears to be pretty strong.   Right now the model data is favoring central and Southern Virginia being hit with a series of thunderstorms… But it is still too far out in to be certain of this.

WEEKEND  # 2   JUNE 11-12 -13.

Right now the early call on the second weekend shows a significant ridge developing in the jet stream over the central lower plains and the delta region.  The GFS and the GFS ensemble is pretty bullish with this pattern building the ridge into the heart of the Midwest and forcing the jet stream north of VA.  This was set up a somewhat drier more, pattern and potentially bring significant heat into Western portions of Virginia. However… The European ridge is somewhat flatter and not as amplified so the Middle Atlantic region could still be in a fatal location for thunderstorm development because of the jet stream not shifting to the north.