Meiszberg Sterling, VA

Forecast Discussion...

Current Analysis
Sterling, VA currently remains under the influence of a high pressure center while it continues to move into the Atlantic. This morning saw the development of fog across the region which is seen in visible satellite imagery.  However this has quickly burned off with the early afternoon heating.  With this though, overcast skies are now being reported in Sterling and surrounding stations which should also begin to break as the boundary layer begins to mix out.  Temperatures will reach into the lower 70's once skies clear out.  On a larger scale, the next system to affect the region currently has a low pressure center near the MI/OH border along with an associated cold front extending down through Arkansas.  This is also seen at the 500mb level in the form of a developing trough over the central plains. 


Short Term
In the short term outlook, the primary concern is the passage of this cold front along with the development of a significant storm system that looks to affect the region soon after.  The latest SREF output shows this front traversing the area by mid-afternoon tomorrow.  This is in close agreement with both today's 12Z NAM and GFS.  Frontogenesis associated with this front is expected to produce precipitation during its passage and bringing with it significant cold air advection which will bring temperatures down into the 50's by Sunday.  A 500mb height and relative vorticity analysis for the movement of this system shows that the shortwave moving through tomorrow is roughly in phase with a secondary shortwave whose base is down into the Gulf of Mexico by 21Z Sat based on the NAM.  These two are forecasted to eventually merge to form a significant upper level trough over the eastern U.S. by Sunday night.  This system is currently expected to be accompanied by very favorable QG dynamics given the amount of vorticity shifting into the region with this system that also looks to be well wrapped up, allowing for warm air advection to reach into the northern side of the surface low.  Nearby terrain also looks to play a role in providing upslope flow once the surface low is located just south of the region, providing for stronger easterly flow.  Continuing into Monday, this low is forecasted by both NAM and GFS to deepen significantly once passing into New England.  The possibility of significant snowfall exists for western PA and especially in higher elevations.  However for the VA/DC region it is expected to remain a rain event.


Long Term
The long term outlook focuses on the lingering influences of the deep low pressure center that should be move out of the VA/DC region by Tuesday night.  Despite the precipitation no longer affecting the area, the overall synoptic flow is expected to come out of the northwest and should be rather strong given a tight pressure gradient.  This flow will be overrunning the nearby elevation terrain and therefore aid in the recovery of the temperatures back into the 60's by Wednesday.  The latest GFS output does put some precipitation over the area for Wednesday however it looks to be lacking the necessary QG support.  This could change by Thursday as the low progresses eastward and a large stationary boundary could setup across the Midwest and east coast. 

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