Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
820 FXUS61 KLWX 061414 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1014 AM EDT Fri Jun 6 2025 .SYNOPSIS... A weak area of low pressure over eastern North Carolina will move offshore by this evening. Meanwhile, a cold front will slowly work east from the Ohio River Valley today and approach the area Saturday before pushing south of the area Sunday. A stronger cold front will cross the area during the middle portion of next week. && .NEAR TERM /THROUGH TONIGHT/... A vort max noted in water vapor imagery is driving a cluster of showers and thunderstorms over southwestern PA and north central WV. Models don`t have the best placement of this convection, but the combination of the forcing and at least some elevated instability to the east suggests this activity could persist in some form across the northern third of the area. Additional storms may fire along the terrain and in closer proximity to a surface low and second shortwave currently over Ohio. This activity will likely affect the western half of the area this afternoon. Showers associated with low pressure over the northern Outer Banks continue to skirt southern Maryland but should not make any addition northwestward progress. Heights will gradually fall over the region over the next 60 hours or through the day Sunday. This will support a lee-side trof this afternoon and promote moisture and instability to support showers and thunderstorms, particularly west of the Blue Ridge Mountains. T-storm activity is expected to spread east and reach the metros during the evening hours, although with weakening intensity. There is a risk of some severe wx this afternoon, mainly for areas west of I-81 and into northern MD and PA. An isolated instance of flooding is also possible in this area due to slow storm motions, precipitable water over 1.5 inches, and one hour flash flood guidance of 1-1.5 inches. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... A cold front will enter the fcst area Saturday and continue to support the risk of showers and thunderstorms Saturday and through the weekend. Both forcing and moisture will be plentiful to support numerous to widespread showers and thunderstorms. Instability will be modest due to widespread clouds and weak lapse rates. Trough axis is expected to shift east of the area Sunday night, which should result in a decreasing trend of showers. However, summer fronts/troughs tend to move slower than model guidance indicate. So, we`ll see about this. && .LONG TERM /MONDAY THROUGH THURSDAY/... A broad longwave trough with an embedded closed upper low is forecast to dive southeastward from the Canadian Prairie Provinces and Northern Plains toward the Great Lakes and eventually the Northeast on Monday and Tuesday. That will place us within southwesterly flow aloft ahead of the approaching trough. Gradual height falls aloft atop a seasonably warm and humid airmass will lead to development of at least weak surface based instability on both Monday and Tuesday. Deep layer shear will also be on the increase ahead of the approaching trough. Showers and thunderstorms appear possible on both Monday and Tuesday afternoon, and a few stronger storms can`t be ruled out given the overlap of instability and deep layer shear present. Most model guidance shows the aforementioned trough progressing off to our east by Wednesday, with weak upper ridging building in for the middle of the week. This should result in drier conditions locally for Wednesday and Thursday. Temperatures should remain seasonable, with highs generally in the low-mid 80s and overnight lows in the upper 50s and 60s. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... A cluster of showers and thunderstorms is cross the Appalachians this morning. This activity would most likely affect MRB, but will have to see what holds together to the east. Additional t-storms are likely at MRB this afternoon, with scattered activity reaching the metro areas after 21Z. There should be a weakening trend with eastward extent, so the PROB30 groups represent closer to a 50 percent chance at IAD and 30 percent chance at BWI. They should dissipate by 02Z, if not sooner. More widespread showers and t-storms are expected Sat into Sun as a cold front slowly crosses the area. Prevailing VFR conditions are expected on both Monday and Tuesday, but temporary drops to sub-VFR conditions may be possible either afternoon. Winds are expected to be out of the south to southwest both days. && .MARINE... Generally, light winds below 10 kt through Sunday. Lightning will be the main threat over the weekend. Winds increase Sunday behind a weak cold front and SCAs may become necessary. Sub-SCA level south to southwesterly winds are expected on both Monday and Tuesday. Thunderstorms may be possible either afternoon. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...ADS/LFR SHORT TERM...LFR LONG TERM...KJP AVIATION...ADS/LFR/KJP MARINE...ADS/LFR/KJP