Forecast Discussion for Willowsford Farm and vicinity from the NWS in Sterling, Virginia
000 FXUS61 KLWX 220800 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 400 AM EDT Wed May 22 2019 .SYNOPSIS... Canadian high pressure will continue to dominate over the region today, shifting offshore by this evening. A warm front will pass through the area late tonight into Thursday. A cold front will approach Thursday night before stalling out nearby for Friday and Saturday. The boundary will likely linger through the remainder of the weekend and into Memorial day, resulting in the potential for unsettled conditions. && .NEAR TERM /THROUGH TONIGHT/... Canadian high pressure will start to shift eastward out of our region as a warm front approaches and moves into our region from the west. As the front moves through our area during the late afternoon period into evening, chances for showers should remain nonexistent due to the upper level ridge axis remaining situated over most of the Mid-Atlantic and SE US. Winds will begin out of the north this morning but as the warm front moves through our region, winds will become southerly leading to advection of warm and moist air into our area. This will lead to afternoon temperatures trending upwards into the mid to upper 70s today with overnight temperature remaining mild in the 60s. Clouds will build into our region from the west this evening and overnight. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... The warm front will pass through the region early Thursday morning and lift off to our northeast. As the front moves through our area there may be enough instability to kick off a few showers during the morning period on Thursday. Once the front moves to our northeast, our region will be in the warm sector ahead of an approaching cold front. A southerly flow will lead to continued warm air advection which will transport moisture and warmer temperatures into our region. Increasing humid conditions along with temperatures rising up into the mid to upper 80s will allow CAPE values to increase into the 1500 to 2500 range. This will be an environment conducive for the formation of thunderstorms if there is a good lifting mechanism or if there is enough daytime heating to break the capping inversion. A cold front is expected to cross into our region Thursday afternoon into evening. There still remains a lot of uncertainty on when this front will pass through our area. The models have been trending quicker with this frontal passage with the GFS being the fastest solution along with having the stronger upper level forcing. The Storm Prediction Center has elevated the areas across extreme north central Maryland to an Enhanced Risk for severe weather with a Slight Risk reaching as far south as DC and mainly north of I-66, while a Marginal Risk is highlighted for the remainder of the CWA. There will be plenty of energy for storms to feed on in this environment and the potential formation of severe storms will rely on the timing of the frontal passage and how much heating can occur before the front moves through our area. The main threat window for thunderstorms and severe weather will be the afternoon period and early evening on Thursday during peak heating. There remains a lot of uncertainty on how widespread thunderstorms and showers will be but POPs have been increased along the Mason Dixon Line to account for the increased SPC risk and new guidance keeping the highest chances for precip over our northern zones. Overnight temperatures will remain mild in the mid to upper 60s. The cold front is expected to move through our region by early Friday. A few showers could linger into the Friday morning mainly along the Mason-Dixon Line in western Maryland. High pressure will build back into our region behind the frontal passage for Friday. Skies will become mostly clear on Friday with a mainly westerly flow. Temperatures during the day will be cooler in the low to mid 80s as compared to Thursday. Overnight temperatures into Saturday will continue to be mild in the low to mid 60s. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Saturday morning, mid to upper level ridging will crest over the Eastern Seaboard with surface high pressure stretched across the region. The high will migrate offshore on Saturday as the flow aloft transitions to more zonal in nature. At the surface, low pressure tracking across the Great Lakes will place the area in the warm sector as winds turn south southwesterly and temperatures run well above normal for the latter half of May. As a result, chance POPs will be highlighted in the forecast, mainly over the higher elevations and near the Mason Dixon Line Saturday afternoon and evening. A cold front will approach from the north on Sunday, lingering nearby through Monday. Daily chances for showers/storms will continue, focused around peak heating hours as shortwave energy tracks overhead, and above normal temperatures and humidity persists. Looks to be a brief reprieve from the heat and humidity on Tuesday as high pressure transits the region. However, another shot of shortwave energy quickly approaching from the northwest may spark late day showers and thunderstorms again over the higher elevations. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... High pressure will begin to shift northeastward out of the our region today. Winds will begin out of the north but will become southerly by this afternoon. Skies will remain mostly clear with a few mid to high level clouds. VFR conditions are expected at this time. Mid level clouds will build into our region late today and overnight as a warm front moves through our area. Some showers will be possible early Thursday but the best chance for showers and thunderstorms will be during the afternoon and evening periods on Thursday. Mainly VFR conditions expected but some MVFR conditions will be possible with showers and thunderstorms on Thursday. Winds will continue out of the south and then become westerly behind a cold frontal passage late Thursday into Friday. Clear skies are expected for Friday as high pressure settles over our region. VFR conditions expected on Friday for terminals Afternoon showers and thunderstorms will favor our mountain zones Saturday and Sunday, with MRB serving to have the best shot of brief sub VFR conditions. Otherwise, predominate VFR conditions are expected with winds favoring a light southerly trajectory Saturday, veering westerly on Sunday as a frontal boundary settles across the region. && .MARINE... High pressure will move northeastward out of our region leading to winds becoming southerly as a front boundary moves through this afternoon into this evening. Stronger winds over the waters will be possible on Thursday as a cold front approaches and moves through the waters. Strong thunderstorms will be possible on Thursday which may require special marine warnings due to strong gusty winds and an isolated waterspout. Small Craft Advisories may be needed Thursday afternoon and into early Friday. Light southerly flow on Saturday will increase Saturday night as a cold front approaches from the north. Marginal SCA conditions will be possible during this time. The frontal boundary will settle near the waters on Sunday, with the gradient remaining weak, however isolated showers and storms will be possible each afternoon/evening. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BKF NEAR TERM...JMG SHORT TERM...JMG/BKF LONG TERM...BKF AVIATION...BKF/JMG MARINE...BKF/JMG
NWS LWX Office Area Forecast Discussion