high risk

Spot on. Forecasted highs for Thursday and Friday are way too warm.

Did you accidentally stumble in here while looking for the Guam forum???

Yeah, the GFS timing would be terrible; hug the Euro.

Beware the midweek back door cold front! A fair amount of guidance has at least the northern parts of the forum much cooler than the far southern parts Wednesday- Friday.

Thanks for noticing! My forecast was pretty good, except that the storms (while sub-severe) persisted all the way east into the DC Metro area this evening. The CAMs were too quick to really disintegrate the line.

Pretty remarkable CAM agreement on an intense line rolling through the area in the early afternoon tomorrow. (The NAM Nest is a bit later than any other guidance, but it has a notorious slow bias on convective timing.) The reflectivities look amazing, but is there really any severe potential with it in the DC area? The wind fields are amazing, and if we had even 500 j/kg of sfc-based cape, we'd be looking at widespread damaging winds and QLCS tornadoes. But there really isn't any instability shown by any model. Maybe the HRRR squeezes out 50-100 j/kg, but it looks warmer than most other guidance. So, I have to wonder if this will be just a short period of torrential rain followed by stratiform. Before I totally poo-poo the threat, however, it's worth noting that sometimes the incredible shear and overall dynamics can drive severe weather with a forced line in an environment with basically no cape, so I won't rule out a damaging event with an isolated brief pinup, but I don't think that it's likely. The better environment actually establishes itself over northern VA and areas to the north and northwest in the evening hours, as the very cold air aloft arrives, steeping lapse rates. Go look at sfc-based cape fields for the early evening hours. The values aren't awesome, but they're notably higher than during the early afternoon event. Wind fields are still decent, so any cells would likely be supercellular have hail and wind potential. Unfortunately, the upper system arrives just a bit too late, and nighttime sfc cooling with reduce the potential as the evening goes on. The best severe threat with this round will be over eastern WV, northwestern VA, and up into PA. Maybe an isolated cell can pop across the DC metro area, and it would have severe potential if it did, but the threat appears low there at this time.

Looking at the 00Z guidance, the timing for Wednesday now appears slower which probably reduces the severe threat for those of us in central MD. Some thoughts: 1) Several CAMs show an intense, forced line of convection sweeping through during the midday hours. Wind fields are intense, but there just isn't any instability until you get south of Richmond, and it's pretty meager down there too. If there is a severe threat with this feature, it's likely well south and southeast of the DC area. 2) As the dry slot approaches and much colder air aloft overspreads the area, convection is likely to form later in the day over western VA and move eastward. Wind fields are weaker but still sufficient for a severe threat, and there may be just enough sfc-based instability for a low-end wind threat and perhaps some hail too. What's not as good is that the timing of the system reduces the instability, especially for areas on the east side of the Potomac. There is still some severe threat, but it's highest over northern VA.

The models all ingest the same weather balloon data.

Uh, because guidance shows actual sfc-based instability this far north…..

Right now, the morning threat appears to be south of the DC area. While the wind fields will be terrific, there likely won’t be sufficient time to advect the unstable air mass far enough north. For now, I agree with SPC that the best opportunity in our area is with the evening front. The wind fields will be weaker, and surface winds may start to veer a bit, but a wind threat will exist if we can get a bit of instability.

GFS has a known progressive bias.

There may be some pretty good height falls with this system, but we typically end up with very widespread clouds and showers in advance of the primary forcing in setups like these. Regardless, it's certainly nice to have something to look at as we wrap up February.

Agreed. The NAM Nest had the band falling apart as it moved east, which was a clue that the scenario shown by some of the other CAMs wouldn’t play out.

That’s not even remotely true. Several models yesterday had a band of light snow moving through the area this morning. It’s a real thing, but it’s just too light. Even if it ended up not working out, LWX doesn’t make up advisories out of nothing.

Several CAMs are showing a band of snow with the ULL pass midday Thursday. There is even bit of instability in the forecast soundings, so some heavier bursts of snow certainly seem possible. And stockage would be very efficient with the very cold temps.

We should all acknowledge as a group that, even if the NAMs are spectacularly wrong on this event, we’re going to miss them like deceased grandparents when they’re retired next year.

Yes! When the 3 km shows details differently than the 12 km, the 3 km is better way, way more than it isn’t.

Absolutely. The problem is that the mesoscale models really weren’t designed for beyond the day 2 period. That doesn’t mean that they’re useless; you just have to use extreme caution.

The wind threat is behind the cold front. Still several hours away for the I-95 corridor

Oh good. You’re back with your incessant 3rd grade understanding of NWP.

I think it's legit. The forecast soundings show potential for good mixing behind the front, and there will be some strong speeds just above the surface.

Several CAMs take most of us into the low 60s Sunday, with the NAM Nest being a notable holdout. Soundings support possible thunder ahead of the cold front.

As expected. The changes between the 06Z and 12Z GEFS were small, and both the 13 and 19Z NBM use the same cycle (00Z) of the EMCWF ensemble.

It ran on time, but they are having huge issues with getting the data to their customers, so no site is able to generate any graphics.

Of course the model ran. The problems are with the dissemination of the output.