April 1, 2024 Outlook

Flood threat, Severe threat,  Snow threat remains……

A start with the flood watches that are in effect and have expanded to Somerset County and I’d expect with all the modeling pointing some of the heaviest Pittsburgh to Johnstown you’ll see Cambria fall in to that watch area as well.

Modeling on the rains just past changeover to snow time

18z HRRR out 48hrs through 2pm Wednesday

Rainfall tallies for round 1 plus round 2(Saturday night, Sunday night/Monday am)

Bittinger 2NW Valley  2.08″

Strong and severe storms may accompany the drenching downpours Tuesday in to Wednesday. May area should hold west of the Alleghenies.

So this aspect will need to be monitored as we go through the next 36-48 hours

Then eyes will transition to the backside wintry aspect.

Snow should begin to mix in Wednesday afternoon across the WV high ground first, then elsewhere across the Alleghenies as we go through the overnight Wednesday.

Accumulations initially across the high Wv locations and lowering. Below 3000-3500′ may melt back off Thursday during the peak diurnal afternoon hours and then start accumulating late day. Thursday night through Friday night should be the main accumulation period.

Temps off the 18z GFS

Potential accumulations at elevations below 3000′ again will be impacted by marginal daytime temps, sun angle, so compression and diurnal melt will be most prevalent in this zone. As you go up it will gradually become less and less as temps will be lower and precipitation will be more persistent. There is no diurnal temp rise across the high ground as it’s precipitating. Temps on the tops Friday afternoon may not get out of the mid 20s as the 850 temps suggest.

  So upslope snowfall thoughts Wednesday P.M to Saturday A.M

You can carry that same type of thoughts on down the Alleghenies.

The northern Alleghenies with a bit less elevation north will battle that daytime mektback, compression, with the areas near and above 3000′ doing the best.

Modeling looks like

These are not mesoscale models and the grid points are much larger. So, manual judgments of elevation, daytime melt, compression are used. This also will include the snow depth maps some post. Those maps have NO physics for elevational gains over a mile or 2  and more of a blended broadbrush. Those snow depth maps fail throughout the entire winter.

While accumulation and depths over a multi day can vary greatly, that variance is less on the tops vs those lower zones that experience more meltback. 

  So far things have nearly held course from what modeling showed later last week. So let’s watch to see how the flood risk, severe risk,  and that winter threat continue to evolve over the coming days.