Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 200128 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 928 PM EDT Tue Mar 19 2019 .SYNOPSIS... High pressure will remain in place over the region through Wednesday. A coastal low will develop off the coast of the Carolinas and move northward into our region Thursday. A cold front will approach our region from the west on Thursday and linger through early Friday. High pressure will build into our region from the Great Lakes through the weekend. Another system will affect our region Monday into Tuesday next week. && .NEAR TERM /THROUGH WEDNESDAY/... Very light to calm winds under a clear sky are leading to radiational cooling this evening as high pressure builds overhead. High clouds are moving in steadily from the west, though, which should cause temperatures to level off after midnight. Lows in the middle to upper 20s are expected for much of the area, expected lower to middle 30s in the major urban/downtown areas. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... High pressure will shift northeastward out of our region through Wednesday evening. As the high shifts out of our region, winds will become southerly leading to good warm air advection into our area. Temperatures during the day on Wednesday are expected to trend upwards into the mid 50s. High clouds will start to build into our region from the west as a cold front approaches from the midwest. Multiple areas of upper level energy will shift eastward toward our region late Wednesday into Thursday. The northern stream of energy will dig southward from the upper Midwest into the Great Lakes region and our area late Wednesday into Thursday. The southern stream is forecast to be kicked southward into the Southeastern US and form a coastal low along the Carolina coast. The models have the two energy streams merging over the Carolinas by late Thursday into Friday. Temperatures on Thursday are expected to warm ahead of the cold frontal passage. The coastal low forming in the Carolinas is expected to move northward into our region Thursday morning into afternoon periods. A cold front will approach at the same time from the west. There is general model agreement that precipitation will start to affect our region some time after 00z on Thursday with best chance being after 6Z. Rain will likely overspread most of the region by the 12 to 18Z period. I have upped the pops slightly in the 00Z to 6Z period to account for some models having the coastal low moving quicker into our region. As the cold front approaches from the west the higher elevations out west could experience a few scattered snow showers. Rain is expected to finally move out of our region by late Thursday into Friday with some showers lingering into Friday near the Mason Dixon Line. Some upslope snow showers can`t be ruled out behind the cold frontal passage Friday morning. && .LONG TERM /FRIDAY THROUGH TUESDAY/... An upper-level low will swing down from the north on Friday, as the coastal low that will bring rain on Thursday departs off to the northeast. As the upper low tracks southward, it will drive a surface cold front through the area Friday afternoon. A few showers will be possible along the surface cold front, and also within the steep low-level lapse rate environment beneath the upper low. Some of these showers could potentially fall in the form of snow or graupel over the higher elevations. Gusty winds will also be possible Friday afternoon and evening in post frontal northwesterly flow. High pressure will gradually build over the region through the day Saturday as shortwave ridging aloft moves into the Ohio Valley. The high will slide offshore on Sunday, which will allow southerly return flow to develop. Both days this weekend look dry, but Sunday will be substantially warmer than Saturday as southerly winds start to transport a warmer airmass into the area. On Monday, disturbances in both the northern and southern streams will start to approach the area. The northern stream trough will be quite dynamic, forcing the development of a large area of high pressure in it`s wake. This high will shift southward in conjunction with the upper trough, driving a powerful cold front southeastward toward our area. The combination of the southern stream disturbance approaching from the Tennessee Valley, coupled with the southward surging cold front could produce precipitation across the area by Monday afternoon. However, the positioning of the front and the resultant chances for precipitation are still rather uncertain six days out. The airmass behind the cold front looks very cold for late March, and wintry precipitation may be possible behind the front, even at lower elevations. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... VFR conditions expected through Wednesday as mid/high clouds build in from the west. As a coastal low approaches from the south and a cold front approaches from the west Thursday, with cloud bases lowering to MVFR Wednesday evening and IFR conditions possible by Thursday morning. As rain moves into our region on Thursday, IFR conditions likely continue. VFR conditions are expected on Friday through the weekend. However, a brief shower can`t be ruled out during the day on Friday. && .MARINE... High pressure expected to remain in place through Wednesday leading to light and variable winds. A coastal low will approach and move through the waters on Thursday leading to the possibility that Small Craft Advisories maybe needed Thursday evening into Friday. A cold front will pass over the waters during the day Friday. SCA level winds appear likely behind this front, and there`s a chance that winds may even reach gale force late Friday afternoon. SCA level winds appear possible Friday Night through much of the day Saturday, before winds gradually drop to sub-SCA levels Saturday Night. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...JMG NEAR TERM...DHOF/JMG SHORT TERM...JMG LONG TERM...KJP AVIATION...DHOF/KJP/JMG MARINE...DHOF/KJP/JMG is the U.S. government's official web portal to all federal, state and local government web resources and services.