|Dew Point:||-4.4°F (-20.2°C)|
|Sea Level Pressure:||30.27" (1024.9 mb)|
Mostly ClearLow: -2
Mostly SunnyHigh: 30 Low: 23
Heavy RainHigh: 44 Low: 30
Rain And Snow Likely then Snow Showers LikelyHigh: 34 Low: 13
Chance Snow ShowersHigh: 18 Low: 6
Mostly clear. Low around -2, with temperatures rising to around 4 overnight. Wind chill values as low as -14. North wind around 7 mph.
Mostly sunny, with a high near 30. Wind chill values as low as -6. South wind 6 to 9 mph.
A chance of freezing rain and a chance of rain after 2am. Mostly cloudy. Low around 23, with temperatures rising to around 34 overnight. South wind 9 to 16 mph. Chance of precipitation is 40%. Little or no ice accumulation expected.
Rain and freezing rain likely. Cloudy, with a high near 44. Southwest wind 14 to 17 mph. Chance of precipitation is 90%. Little or no ice accumulation expected.
Rain before 1am, then rain and snow. Cloudy, with a low around 30. Southwest wind 8 to 13 mph. Chance of precipitation is 90%. New snow accumulation of less than one inch possible.
Rain and snow likely before 7am, then snow showers likely. Mostly cloudy, with a high near 34. Chance of precipitation is 70%. New snow accumulation of 1 to 2 inches possible.
A chance of snow showers after 2am. Mostly cloudy, with a low around 13. Chance of precipitation is 40%.
A chance of snow showers. Partly sunny, with a high near 18. Chance of precipitation is 40%.
A slight chance of snow showers before 3am. Mostly cloudy, with a low around 6.
... Building high pressure will provide another very cold night. Precipitation chances return Tuesday night with approaching low pressure.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Made minor adjustments to sky cover and temperatures overnight, but the forecast remains on track overall. The remaining Wind Chill Advisory for the ridges will likely be allowed to expire on time at 06Z. Otherwise, another bitterly cold night is in store for the region. Lows will be near or a bit below zero in most locations. As high clouds arrive from the southwest later tonight, at least southeast Ohio is likely to see a slight rise in temperature during the predawn hours.
SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/... A 1040mb surface high will quickly shift east of the CWA early Tuesday morning, with strong low level warm advection expected beneath a transient mid level ridging. An impressive diurnal spread is expected, especially south and west of Pittsburgh where the snow pack is light to non-existent, and highs may approach 40 degrees late in the day. Highs should approach freezing around Pittsburgh, and will be restricted in the mid 20s across the I-80 corridor and into the eastern mountains where high pressure will hold out the longest.
Temperatures will fall back early Tuesday evening before skies cloud up in advance of a deepening storm system over the Midwest. Very strong low-mid level warm advection will occur Tuesday night coincident with sharp pressure/height falls ahead of the deepening trough. Deep layer flow trajectories off the Gulf of Mexico will quickly reach the area on a 50 knot low level jet early Wednesday morning. Although all model solutions show a warm nose aloft, prefer the much warmer NAM solution given its typical handling of these types of systems.
This suggests that precipitation will likely begin as rain* with perhaps some sleet across the far northeast at onset. The caveat is that we are coming out of a several day deep arctic plunge. Other than areas which reach the upper 30s tomorrow, surface temperatures will remain well below freezing at the onset. Having worked several events in my career in similar scenarios (arctic outbreak to rapid warmup), it is always a challenge figuring out when freezing rain will cease. With heavier precipitation arriving for the Wednesday morning commute, it's key that we get this right and perhaps err on the side of caution. I've seen freezing rain accrue until air temperatures reach the lower 40s in prior arctic events, and thus will keep a mention of FZRA for areas north of I-70 as well as the WV/MD mountains through mid morning Wednesday despite hourly temperatures above freezing. Headlines may be necessary in that 06Z to 15Z.
Rain, heavy at times, will continue through Wednesday and at least across the southeast zones into Wednesday evening as several lower tropospheric waves ridge through the mean trough position. Deep convection along the southwest tail of the frontal zone will only act to further moisten the local environment, with mid-upper moisture carried by a strong southwesterly jet. Not surprisingly, forecast precipitable water values in the 0.80 to 0.90" range are at the upper echelon of climatology for Jan 23rd, and I am expecting a widespread 0.75" to 1" of QPF for the region. This rainfall, coupled with snowmelt, on top of rapid ice growth on area rivers over the past 36 hours, yields a moderate to high confidence that hydrologic issues will follow for the mid-late week.
A surface cold front will sweep across the region Wednesday night, but will be coincident with rapid dry advection aloft. Thus, expecting that any changeover to snow on the backside of the system will be inconsequential with maybe an inch or two max of upslope snow in the WV/MD mountains through Thursday morning.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... The longer term period suggests a very high confidence of much below normal temperatures. Highly amplified ridging over the western US, coupled with an incredible sub 500dm vortex over southern Ontario, will lead to repeated clipper systems bringing periodic snows and a series of arctic intrusions. Cut guidance temperatures in the extended, perhaps not enough.
Best chance for minor snow accumulations looks to be Saturday night, but could change given the speed of these systems embedded within a very fast polar jet branch.