... High pressure will result in dry conditions and seasonable temperature to start the work week. Rain appears likely on Wednesday with continued precipitation chances through the end of the week, while temperature hovers at or above normal.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 750 PM Update: Few changes were necessary to the forecast as high pressure prevails across the Upper Ohio Valley and Allegheny Mountains. 00Z RAOB shows a well-mixed boundary with plenty of low- and mid-level dry air, which allowed RHs to drop to around 18-25 percent across much of the forecast area. Wind will go to near calm overnight under a mostly clear sky (or just some thin cirrus), which will allow temps to quickly drop back below freezing.
12Z RAOB-suggested drying via deepening boundary layer continues as full insolation promotes mixing and occasional gustiness. This fcst deviates from NBM, which appears to be bias-correcting dewpoint temp in the wrong direction. Relative humidity values likely will reach the upper teens to lower 20s over the next few hours and maintain a marginal wildfire risk, though restrained wind precludes the need for headlines.
Building high pressure will maintain abundant sunshine and warmer temperature this afternoon with occasional swly gusts between 10 mph and 15 mph during the afternoon.
Overnight minima are forecast to drop to the lower 20s/upper teens as light wind and minimal cloud coverage promote nocturnal radiational cooling.
SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Rising heights will maintain dry weather and warming trend Tue with highs several degrees above normal. Flattening of the upper ridge will support ewd advection of high clouds, decreasing insolation through the day.
Continued abundant dry air above a shallow morning boundary layer is likely to spell a second day of minimum dewpoint temperature considerably below NBM-forecasted values, given the ensemble's bias-correction toward higher moisture. Fcst was adjusted toward the dry side for the second day in a row, although mixing may be slightly more limited than Mon by increasing aftn cirrus.
LONG TERM /WEDNESDAY THROUGH MONDAY/... Rain looks likely to return Wed as a Colorado low ejects newd into the Midwest and Gulf moisture streams nwd within a deep sly fetch. Drier air from the lingering ridge and weak ascent should limit rain amounts to less than one-quarter inch across the region.
The potential for heavier precipitation will increase sharply on Thu night and continue into the weekend as PWATs jump to 2-3 standard deviations above normal and a sfc low develops along a stationary boundary and tracks across the Ohio River Valley. Probability for excessive rainfall is higher than normal with this system, which seems reasonable as several analog pattern matches were associated with flood reports, and soil moisture should be elevated after prior days' rainfall.