330 FXUS61 KLWX 020831 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 431 AM EDT Tue Jul 2 2019 .SYNOPSIS... High pressure will shift off the Mid-Atlantic coast today and reside over the western Atlantic through the end of the week while upper- level high pressure builds from the south. Hot and humid conditions will persist through the weeks end along with chances for showers and thunderstorms. A cold front will approach this weekend, promoting continued unsettled conditions, before settling to our south early next week. && .NEAR TERM /THROUGH TONIGHT/... High pressure will slide off the Mid-Atlantic coast today as a return flow sets back up over the region. This will allow for temperatures and humidity levels to climb upwards after the brief break observed the past 36 hours or so. With forecast 850/925mb temperatures likely running the warmer today compared to the next couple of days thanks to warm air advection, have upped temperatures a bit this afternoon into the low to middle 90s. Wouldn't be surprised if today turns out to be the warmest day of the week temperature wise. While dewpoints are on the rise and will continue to be through tonight, heat indices this afternoon should hold in the upper 90s to near 100 degrees in the warmest locations. As a result, no heat advisory headlines are planned for today. That being said, be sure to stay hydrated and take frequent breaks in the shade if spending any lengthy time outdoors this afternoon and early evening. With the increasing temperatures and low level moisture, instability will be on the rise as well today. The best mid-level forcing will remain well to our north across northern PA/OH where a stationary boundary will be lingering. That being said, do expect at least a chance of showers and storms this afternoon and into this evening, with our northern and western zones favored. Latest high resolution guidance is indicating widely scattered activity west of the Blue Ridge Mountains and across northern/northeast MD late this afternoon with daytime heating maximized. Mid-level lapse rates will remain poor, but with ample surface heating, low level lapse rates could support some stronger storms as CAPE values maximize in the 1000- 1500 J/kg range. With 0-6km shear remaining at or below 20kts, organized severe threat appears low, but with any stronger storms that do form, damaging wind gusts would be the primary threat. A Marginal Risk for severe is highlighted by SPC over northern/western MD and portions of the eastern panhandle of WV. Showers and storms will wane this evening, with a few showers possible overnight, however most will remain dry. The humidity will continue to tick upwards through the night as dewpoints creep into the upper 60s to near 70 degrees. So a warm and muggy night is on tap with temperatures sticking in the low to middle 70s. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Wednesday through Thursday the area will reside on the northern periphery of the surface and upper level ridging over the Deep South. There will be better coverage of showers and thunderstorms each day as the mid-level forcing does improve thanks to waves of shortwave energy making their track southward across the area. As typical with a hot and humid summer pattern, the showers and storms will be focused during the afternoon and evening hours. Low level moisture will continue to increase with dewpoints holding serve in the low to middle 70s, which can be categorized as oppressive for the Mid-Atlantic region. This moisture increase at the surface, increasing PWATs to around two inches throughout the atmospheric column, and afternoon temperatures in the lower 90s will provide plenty of fuel for the showers and thunderstorms. Ample CAPE is expected each day, but a bit more of a westerly flow on Wednesday could limit coverage bit more compared to Thursday. While shear is expected to be limited a bit, thinking the potential severe threat will be highlighted with damaging wind gusts and some hail. With the moist airmass in place and slow storm motion, heavy rain and localized flooding will also be on the table. Plenty of clouds and elevated rain chances should help keep temperatures in the upper 80s to lower 90s, with heat indices currently forecast to remain just below advisory level each afternoon. Will have to continue to monitor this over the next couple of days, as dewpoints will be quite high in the 70s. && .LONG TERM /FRIDAY THROUGH MONDAY/... Showers and thunderstorms will be possible Friday and Saturday with warmth and moisture feeding northward ahead of a boundary and upper level energy from the west. Computer models indicate a persistent CAPE value above 1500 J/kg. Temperatures will range from the mid 80s to low 90s with dew points up in the 60s to low 70s. With the abundance of low-level moisture, thunderstorms will be capable of producing heavy rainfall and hail. Damaging winds will also be possible, especially Saturday. A surface front will approach from the northwest and move through our region by Sunday afternoon. Widespread rain and thunderstorms will be possible again this weekend ahead of the front early and midday Sunday. There is a chance that the surface front pushes to our south Sunday afternoon and night, giving a short-lived break from widespread showers and storms. Temperatures Sunday may be a couple degrees cooler. As a return flow develops Monday and continues into Tuesday next week, humidity will be on the rise again along with temperatures. Showers and thunderstorms could from ahead of an upper level disturbance later Monday into Monday night. Flooding could be a threat should showers and thunderstorms become nearly stationary. Temperatures will hover near 90 degrees most places. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... Prevailing VFR conditions expected today at the terminals with the potential for afternoon showers and isolated thunderstorms. Based on the latest guidance, MRB/BWI/MTN would have the highest chances of brief sub VFR conditions this afternoon and early evening. Afternoon and evening showers and thunderstorms will continue to plague the terminals both Wednesday and Thursday, with periods of sub VFR conditions possible at all terminals. Winds will remain at 10 knots or less out of the west southwest. VFR conditions each morning Friday and Saturday could quickly go to IFR conditions for a brief period of time should showers and heavy thunderstorms develop near the terminals. Once through, conditions will improve toward MVFR and VFR. Terminals that receive heavy rain during the daytime hours could pose a patchy fog threat. Winds generally southerly Friday and southwesterly Saturday and averaging 5 to 10 knots with higher gusts in thunderstorms. && .MARINE... High pressure over the western Atlantic will yield a weak gradient across the waters and sub SCA conditions. Threat to boaters over the next few days will be afternoon/evening showers and thunderstorms, some of which could be strong to severe. Locally gusty winds may require the need for SMW's each day. No hazardous weather expected at this time Friday through Saturday night. Heavy thunderstorms could pose a threat for brief damaging winds, so Special Marine Warnings may be warranted Friday and again midday Saturday. Winds southerly becoming southwesterly by Saturday around 10 knots with higher gusts in thunderstorms. && .TIDES/COASTAL FLOODING...Updated A Coastal Flood Advisory is in effect for the shoreline in Anne Arundel County until 8am this morning as tidal anomalies around 1 foot above normal area expected during this mornings high tide cycle. Anomalies will remain elevated the remainder of the week thanks to southerly flow and high pressure parked over the western Atlantic. Current forecast is to maintain Action stage at a majority of our sites during high tide, but the sensitive locations will run close to minor flood, and require close monitoring in the coming days. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until 8 AM EDT this morning for MDZ014. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BKF NEAR TERM...BKF SHORT TERM...BKF LONG TERM...KLW AVIATION...BKF/KLW MARINE...BKF/KLW TIDES/COASTAL FLOODING...BKF