Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 200758 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 358 AM EDT Mon May 20 2019 .SYNOPSIS... A cold front will cross the area this afternoon and early evening. Sprawling Canadian high pressure will dominate in its wake through the middle portion of the work week. This high will shift offshore Wednesday night as a frontal boundary lingers near the Mid Atlantic to finish out the week. && .NEAR TERM /THROUGH TONIGHT/... Low pressure over the Great Lakes early this morning is stretching a cold front on the doorstep of the Ohio Valley, as a stationary boundary is kinked along the Mid Atlantic seaboard. Skies overhead are partly cloudy with the bulk of shower activity north of the Mason Dixon Line. Temperatures remain quite mild this morning, hovering in the middle 60s over our mountain zones, with low to middle 70s being observed elsewhere. Dewpoints in the low to middle 60s continue to give that summer-like feel in the air. The aforementioned cold front will track eastward through the Ohio Valley this morning, crossing into the CWA this afternoon through early this evening. Guidance in fairly good agreement of any shower/storm activity associated with its passage to be mainly focused along and east of the Blue Ridge mountains. This is where the best CAPE (1000-1500 J/kg) and shear resides, but overall instability will be down compared to the past couple of days. The threat for a few strong to marginally severe storms does exist east of the Blue Ridge into the metro areas, including southern MD. The primary threat with any strong storm that develops along the front will be locally damaging winds and hail. Temperatures are expected to soar well into the 80s, but likely a degree or two cooler than Sunday given increased cloud cover associated with front and 850 temps running a touch cooler as well. Precipitation will push off to the south and east shortly after sunset this evening, as drier air filters in behind the frontal passage. This will allow for decreasing clouds, lower humidity, and cooler temperatures in the 50s overnight. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Sprawling Canadian high pressure will build down of the Mid Atlantic from the Great Lakes Tuesday through Wednesday. Gusty northwest winds on Tuesday will yield much cooler temperatures in the low to middle 70s area wide, moderating slightly on Wednesday but still holding in the 70s. The strong and complex system impacting the southern/central Plains the next couple of days will lift northward into the upper Midwest late Wednesday and Wednesday night. This will lift a warm front toward our region Wednesday night as the high shifts off the coast. This will likely bring an increase in cloud cover Wednesday night, as well as increasing shower chances by early Thursday morning, mainly west of the Blue Ridge. && .LONG TERM /THURSDAY THROUGH SUNDAY/... An upper level high pressure system will be situated over the southeastern US through Sunday. There is good agreement that this upper level high will be in place over SE US but their remains uncertainty on how far south the high will settle. This means that their could be the potential for pop up showers and thunderstorms through Sunday depending on the exact location of the high. These storms/showers would be kicked off by shortwaves moving through the system. The presence of this high means that temperatures will trend upwards through this week with temps potentially hitting the 90 degree mark by this weekend. We will have to continue to monitor how this setup progresses to determine the potential for any showers and thunderstorms later this week. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... A cold front will cross the terminals this afternoon and early evening. Predominate VFR conditions are expected, but scattered showers and isolated thunderstorms could yield a brief episode of sub VFR conditions at IAD/DCA/BWI/MTN between 18-21z. Confidence is low in coverage at this time, so will include further detail in the TAF as timing/confidence increases. The front will push to the south and east of the terminals this evening, with west northwest winds taking hold overnight. Canadian high pressure will build over the terminals Tuesday through Wednesday, with gusty northwest winds on Tuesday slacking and becoming light through Wednesday night. No threat for precipitation or sub VFR conditions Tuesday and Wednesday. VFR conditions expected Thursday through Friday but brief flight restrictions could be possible at terminals if afternoon showers/thunderstorms form and move through an area. && .MARINE... A cold front is expected to cross the waters this afternoon and evening. Gusty southwesterly breezes are expected ahead of the front, thus an SCA is in effect. A line of showers/storms is expected with the frontal passage, which could require the need for Special Marine Warnings in any stronger storm packing gusty winds. After a bit of a lull in winds in the wake of the frontal passage, the gradient is expected to tighten Tuesday morning, thus SCA conditions expected once again. As high pressure shifts over the region Tuesday night through Wednesday night, light winds will prevail with no threat of gusty showers/storms. High pressure will be in place over the region with light winds within the mixed layer. This suggests that Small Craft Advisories aren`t expected at this time for Thursday and Friday. && .TIDES/COASTAL FLOODING... Tidal anomalies remain elevated this morning ahead of an approaching cold front. Minor flooding is expected at DC/Annapolis this morning, and monitoring trend the last several hours, looks possible at Baltimore as well. Have a couple more hours to mull over the potential of minor flooding at Baltimore before going with an Advisory. With the frontal passage this afternoon/evening, anomalies are expected to fall. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until noon EDT today for DCZ001. MD...Coastal Flood Advisory until 11 AM EDT this morning for MDZ014. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ531>534-539>541-543. Small Craft Advisory from 2 AM to 6 PM EDT Tuesday for ANZ530>543. Small Craft Advisory from 8 AM this morning to 6 PM EDT this evening for ANZ530-535>538-542. && $$ SYNOPSIS...BKF NEAR TERM...BKF SHORT TERM...BKF LONG TERM...JMG AVIATION...BKF/JMG MARINE...BKF/JMG TIDES/COASTAL FLOODING...BKF

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