Check on where the rain is now with the Weather Journal’s radar view
UPDATE 4 PM, 5/5: FLOOD WATCH EXPANDED TO INCLUDE ALL OF ROANOKE/NEW RIVER VALLEYS WESTWARD/SOUTHWESTWARD ALONG BLUE RIDGE, I-81 AND I-77 CORRIDORS — Widespread 2-4 inches locally 4+ projected through Wednesday evening — Heaviest rain likely Monday and Tuesday. END UPDAATE
UPDATE 7:45 AM: Most forecast guidance this morning suggests the main area of rainfall will not arrive in the Roanoke and New River valleys until late in the afternoon or perhaps even this evening. It will slowly advance through the area west of Interstate 77 today. The heaviest rain is not expected until Monday and early Tuesday. END UPDATE
The swirl centered over Arkansas on Saturday evening is plainly visible in this water vapor satellite shot, with the bright bands of moisture streaming around and spiraling toward the cold center. This is the cut-off upper-level low that is starting to edge eastward, with all the speed of a snail in molasses. This constant spin to our west for the next couple of days will mean a consistent flow of moisture off the western Atlantic into the higher terrain of the Appalachians. Bands of rain now crossing Georgia, Tennessee and Kentucky — just edging into far southwest Virginia late on this Saturday night as I type this — will ever so gradually edge eastward. It’s difficult to tell exactly when the rain will start at any given location, but the Roanoke and New River valleys may get in some (or maybe most) Sunday daytime hours dry or with just a few showers before the bulk of the rain arrives. Once it arrives, though, it will rain intermittently for a couple or three days, and some of those amounts could be heavy, especially from Sunday night through Tuesday morning. Projections of rainfall are generally in the 1 to 4 inch range for our region. The Blue Ridge will provide the greatest lift for the wet southeasterly breezes, and that is where a flood watch has been issued through Tuesday morning, for Roanoke, Montgomery, Franklin, Floyd, Carroll, Patrick and Grayson counties, with some localized 4+ amounts possible, especially toward the North Carolina border. Though accumulating snow fell as far south as northwest Arkansas underneath the chilly swirl, it appears unlikely that this will occur as the low moves eastward — the cold center of trapped Canadian air is slowly warming, and moist southeasterly breezes off the warm ocean waters are likely to keep temperatures and dew points aloft too warm for snow even at the highest elevations. If there is any at all, it would probably occur at 5,000+ elevations beneath the upper-level swirl late Monday or Tuesday. High temperatures, though, will be well below normal with highs on Sunday and Monday possibly not getting out of the 50s in most Southwest Virginia locations, depending on when the rain starts.
Once this low finally lollygags to the East Coast and then possibly gets caught by the jet stream and pulled northeastward, we will probably get a few days of warmer, drier weather.