Saturday, April 18, 2015

Rain, Some Storms, and then a Cool Down

(Update: Sunday 4/19 12:30pm)
Rain is on the door step...already moving into southern portions of the Shenandoah Valley.  The National Weather Service has issued flash flood watches for 1-2" of rainfall potentially causing smaller streams to rise out of their banks. Once again, the best shot for this will be right along the blue ridge where some upslope enhancement will come into play. 

Radar 11:57 am
End update

(Posted Saturday 4/18 7:15 pm)

After a nice start to the weekend, a low lifting north into the Great Lakes will bring a slug of Gulf moisture into the area Sunday. Rain will start in the far southern Shenandoah Valley (Covington, Lexington) by late morning...the central Valley (Staunton, Harrisonburg) shortly after lunch time...and the northern Valley (Winchester, Front Royal) by mid afternoon.  Rain will be steady (even heavy at times) and continue into the overnight.  Expect total rainfall through Sunday night to fall in the 1.00-1.50" range with locally higher amounts (especially along the Blue Ridge).  This may be enough for isolated flash flooding issues.

Simulated Radar for Sunday Evening
We will get a break during the day Monday as the first wave exits off into New England.  There may even be a few peaks of sunshine during the afternoon.

Simulated Radar for Monday Afternoon
A cold front will then approach from the west firing up another round of showers and even a few thunderstorms.  There is the potential for some of these to become strong to severe...with better chances east of the Blue Ridge where instability will be greater.  With that said, certainly still something to watch in the Valley.  Right now, timing of the frontal passage looks to be during the evening (6-10 pm) which will provide our best opportunity for storms.

Simulated Radar for Monday Evening

Looking ahead, a large upper level low will get stuck in eastern Canada filtering in Canadian air on consistent west to northwest winds for the majority of next week.  Although down-sloping will keep things from being too cold, still expect below normal temperatures throughout this period.  Long range indications show the brunt of this cool down arriving next weekend when a few higher elevation snow flakes may even come into the picture.  As I mentioned before, it's not all that uncommon for late April or early May central Appalachian flakes...actually seems to be more of the norm. 

850 MB Map for Mid-Next Week Showing Stubborn Upper Level Low Filtering in Colder Air

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