Forecast Discussion for Willowsford Farm and vicinity from the NWS in Sterling, Virginia
000 FXUS61 KLWX 281858 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 258 PM EDT Sat Mar 28 2020 .SYNOPSIS... A front will stall out near the Appalachians into southern Virginia through tonight. The front will then try to lift north as a warm front early Sunday, before a cold front moves through from the west late Sunday. High pressure will be in control Monday into Tuesday. A low pressure will then approach from the southeast U.S. Tuesday night before departing off the mid- Atlantic coast on Wednesday. && .NEAR TERM /THROUGH TONIGHT/... Latest surface analysis continues to suggest that the surface cold front remains near the Virginia/North Carolina border. However, the frontal boundary aloft has tracked north, which has pushed any daytime convection across Pennsylvania/New Jersey. But, the east flow has permitted a wedge of low clouds to remain trapped across the Baltimore-Washington area, with its southern edge near Charlottesville, banked up against the Blue Ridge. Low clouds has also spilled over the Catoctins to include Cumberland, Winchester, and Hagerstown. Satellite images clearly reflect the have and have-nots. As the maritime flow continues to deepen, anticipate the low level clouds to thicken, with fog to develop as well. At this point, believe it will be more of a low cloud issue as winds won`t go calm, but fog will be locally dense across the ridges as these areas will be within the cloud bank. Given the low-level saturation, don`t believe that temperatures will go far tonight. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... Sunday will start with ample low clouds and fog attempting to lift. How quickly it does so may be the key to the forecast. Believe there will be a sharp inversion, with a warm nose which could be as warm as 19C near 925 mb. A cold front will approach during the day, and cross the region during the afternoon, during peak heating (18-00 UTC). There will be ample shear across the region. Instability will be the question. If the wedge holds, then instability will be minimal and the front would either come through dry or as a few showers (with perhaps an elevated rumble of thunder). But, if the wedge does manage to mix out, then MUCAPE may exceed 1000 j/kg. Given the other ingredients in place, that would be supportive of robust thunderstorms. There are guidance members on each side of the fence. After collaboration with SPC, decided that the conditional threat great enough to at least mention somehow...hence Marginal Risk of severe. Am maintaining a chance of precip crossing the area in the database, with a slight chance of thunder. It may be that both solutions are correct; ie: cool/stable air across northern Maryland while moist/unstable air present across central Virginia and southern Maryland. Will be monitoring later cycles to discern these details. Sunday night into Monday a deep cyclone will build across the Great Lakes. The area will experience high pressure but westerly flow and cold advection. Lows will be in the 40s again by Monday night. && .LONG TERM /TUESDAY THROUGH SATURDAY/... An upper level trough over the southern Plains will drop southward through the southern parts of the mid-Atlantic and the Carolinas Tuesday into Wednesday. A surface low associated with this trough will move to our south Tuesday afternoon and into Wednesday morning. The main area of precipitation should be situated to the south of our forecast area over the Carolinas and the southern portions of Virginia. As the main forcing remains to our south, the precipitation that we observe in our region will likely be caused by a combination of overrunning precipitation and an easterly flow off of the ocean. If this system tracks further northward, our region has the potential to experience heavier precipitation mainly late Tuesday and into Wednesday morning. Precipitation and an easterly flow will lead to daytime temps running near to slightly below normal for this time of the year in the 50s and lower 60s with overnight lows in the 40s High pressure builds into our region behind the exiting low Wednesday afternoon and remains over our area through Thursday. Light winds out of north will lead to cooler conditions over our area. Temperatures will continue to hover in the 50s with overnight lows in the 40s on Thursday. Another cold front is forecast to approach and move through our region Friday and into early Saturday. Models have some decent agreement on the subtropical jet moving northward and phasing with weak jet over the midwest and mid-Atlantic. This phasing will combine with a frontal passage to bring precipitation to our region once again. The main limiting factor will be a westerly flow transporting drier air into our area. We will need to monitor the strength of the jets to determine further hazards for end of next week. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Flight conditions straddling between MVFR and IFR, but across BWI/MTN the marine flow spreading inland has resulted in conditions on the verge of LIFR. Low clouds and fog will continue to spread inland, with LIFR widespread overnight. Conditions will slowly improve Sunday. How quickly this transpires still in doubt. A cold front will be crossing the terminals this afternoon. If the clearing comes by midday, then strong thunderstorms possible along with the frontal passage. Otherwise it may be a dry front. VFR will return Sunday night, continuing through Monday. SubVFR conditions are possible late Tuesday and into Wednesday due to rain and an easterly flow. VFR conditions should return Wednesday afternoon and continue through Thursday as high pressure builds over our region. && .MARINE... Light northeast winds (at or below 10 kt) will continue across the waters this afternoon into tonight. Low clouds and fog will be thickening through the night. Winds will likely veer south tomorrow as the marine wedge lifts. Its unclear how quickly this will happen, but any clearing would be followed by a threat of thunderstorms with gusty winds late Sunday afternoon. Conditions will improve Sunday night, but winds shouldn`t be high enough to need Small Craft Advisories. No Small Craft issues expected on Tuesday as well, but Small Craft Advisories may be needed on Wednesday due to a northerly flow. && .TIDES/COASTAL FLOODING... Water levels hovering around a foot to a foot and a half above astronomical normals. Do not anticipate much change over the next day or two. That suggests that Action stages will be threatened with each high tide, especially the daytime cycle which is the higher of the two. Some low-end minor inundation possible, especially near Piney Point. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...HTS SHORT TERM...HTS LONG TERM...JMG AVIATION...HTS/JMG MARINE...HTS/JMG TIDES/COASTAL FLOODING...HTS
NWS LWX Office Area Forecast Discussion