Cool to Rule First Half of May (04-30-2011)

Enjoy your splendid weather this weekend as once this passes, it looks as if yet another round of unsettled weather will be very close by until the persistent NW flow takes over later this week and through the middle of the month.  While we in the mid-Atlantic and northeast will enjoy a nice weekend, severe weather will yet again rear its ugly head down in the Arklotex region of our country; albeit not nearly as fierce as what was just experienced this past week in that same general region.  This is thanks to another powerful spring mid-latitude cyclone that is maturing in the northern plains as you can see from the map below:

Once this storm pulls NE into O Canada, the associated fronts will move east with a little resistance from the upper ridge in the SE US.  That is what will cause our unsettled conditions for Monday....but we may stay mostly dry as the upper ridge holds tough and keeps the wetness at bay to our west....(Jason Bay OPS of .898 since his return but with 8K in 27AB....sorry I digress....ADD you know!).  However, by Wednesday a stronger system will be affecting our region with much greater upper air support that could lead to a bout of some moderate severe wx depending on the timing of storm passage.  It's strange, but this synoptic set up could also support snowfall in the mountains of western PA, and western MD...up into New England!  If the storm comes through during the max heating of the day, I do believe that severe T-storms will develop with this dynamically active system SE of the mountains......

Once that passes, the NW flow will dominate as far as the modeling can see.  I am becoming more and more confident that May will end up being ~2-4ºF below normal for the entire month which is quite a deviation from normal.  Below is the ensembles depiction of the middle of the 2nd week of May being quite cool in the middle of the atmosphere. 

As a result, instability will rule and ample opportunity for showers and T-storms will be prevalent.  It will obviously not be as wet as this wettest April on record we've just experienced (9.46 inches for the month of April 2011 at KMDT), but soil moisture will remain high through the middle of the month at the very least.  The map below was created a week ago, so the green areas will expand after this past week's rainfall!

As for the upcoming Derby Day forecast, timing is difficult, but it looks as if the Oaks could be warm and wet while the Derby cool and dry.  Another vort max will be spinning under a large upper low and making the visitors to Churchill Downs either delighted or drenched.  For us during that Friday-Saturday time frame, the weather looks cool and dry.....but that is a week away.

To alleviate that uncertainty, any attendee or interested party should simply pick 3 numbers and box them for $1 all day in exactas.  In a 12 race card, that investment of $72 could possibly pay sweet dividends if just one or two of your races hit!  And you get a heartbeat at that....and not just from watching the approaching cumulonimbus!

Enjoy the beaytiful weekend!

Smitty

AA:  Rain nearby all week after Sunday, most likely Wednesday, cooler and drier end of the week.  Run for the Roses on Saturday; beat the early favorite of Uncle Mo!