313 FXUS61 KLWX 020753 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 353 AM EDT Fri Aug 2 2019 .SYNOPSIS... A stalled front and upper level trough will remain in our vicinity into the weekend. The front may push southward Sunday and then lift back northward early next week. && .NEAR TERM /THROUGH SATURDAY/... Latest surface analysis depicts a stationary front straddling the region from southwest to northeast. A very weak surface low is present along the boundary in Virginia. Aloft, a potent but rather small shortwave and vort max is moving northeastward across the region. These features are giving rise to a cluster of showers and storms, mostly south of DC proper. Short-term guidance suggests this cluster will continue to advance northeastward through the next few hours, possibly reaching DC proper, but definitely affecting the southern and eastern suburbs. Locally heavy rain may cause some flooding, but the area of concern is a bit too small for a flash flood watch. An isolated severe storm is also possible, but overall the storms should just produce a lot of lighting and heavy rain. Elsewhere around the region, the weather is mostly quiet, with clouds and patchy fog. This should change quickly later this morning as limited insolation allows instability to build. Expect widespread showers and storms to build elsewhere in the region as the day progresses, assisted by another, weaker shortwave approaching in the mean trough currently over the region. Shear is minimal, but CAPE is quite high, progged potentially to 2000-3000 j/kg thanks to the cool pool aloft. Combined with relatively slow storm motion, this will result in both a marginal severe and flood risk. However, its hard to pinpoint an area most likely to receive severe and flooding, so have not yet issued any flash flood watches for later today, instead opting to allow day shift to re-evaluate latest guidance in the morning. However, the severe and flood risk is definitely present in most of the forecast area today. Plentiful clouds will keep temps down, so expecting highs to mostly be in the low to mid 80s. Later tonight, the second shortwave starts to pull out, but instability may linger. Thus, while storm coverage is likely highest early, it may linger through the night once again. Lows will be in the 60s to near 70. On Saturday, the flow becomes more zonal, and while the front will be present, a dry layer moving in aloft combined with the lack of a more substantial upper-level disturbance will result in a decrease in storm coverage. That said, the risk of isolated flooding and severe will remain, though muted. Highs probably rise a bit higher than today, but still mostly 80s. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... Saturday night, the flow will become northerly as the front drops further south, and with zonal flow aloft and no disturbances, any storms should wind down quickly. Lows mainly in the 60s. On Sunday, the front will stall again, but this time a bit south of our forecast area. However, a weak disturbance will move in aloft during the afternoon and evening. Thus, the chance of showers and storms will diminish, but does not completely end. Highest risk on Sunday will definitely be further south, closer to the front, with decreasing risk of storms towards the PA line. Highs will be hotter, with readings approaching 90 thanks to greater sunshine, but this will also add to the CAPE available for storms later in the day, if they can manage to form despite the drier air north of the front. The passing disturbance at night may mean that despite the front being south, a few storms may linger overnight Sunday night. Lows will be mostly in the 60s. && .LONG TERM /MONDAY THROUGH THURSDAY/... Not a lot of change through the long term period. Broad trough will remain across the eastern US through the period, punctuated by passing shortwaves embedded in the mean flow. The surface front may start south of the region Monday morning, but then push back north as the week progresses. Thus, the risk of showers and storms will remain, and the northward motion of the front means that temperatures and humidity will also likely rise as the week continues. There are hints from some models that a stronger trough and front may push through by week's end, bringing a break from the storm threats, but confidence on this remains low. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... Primarily VFR through early next week. The main concerns will continue to be scattered thunderstorms, primarily during the afternoon and evening hours each day. However, the risk extends into the overnight and morning hours today and again Saturday thanks to stronger upper-level disturbances. Locations which receive rain and then see skies clear somewhat during the night will be subject to reduced visibility in fog, but it should be focused on late night and early morning hours, with fog breaking quickly after sunrise. It should also be primarily a risk for CHO/MRB/IAD, with a lesser threat closer to the cities and waters. && .MARINE... Sub-SCA winds through Tuesday thanks to stationary frontal boundaries and a weak gradient. Main concern through the entire period will be for gusty thunderstorms necessitating special marine warnings. Highest risk is today, decreasing a bit Saturday and a bit more Sunday, then possibly increasing again by Tuesday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...RCM AVIATION...RCM MARINE...RCM