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January: Medium/ Long Range: May the Force be with Us....


Weather Will
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19 minutes ago, yoda said:

Quite the temp gradient on the 12z UKIE right after the storm; on monday night, DCA is 22 while CHO is 3

Same thing Tuesday night... DCA 27, EZF 11, CHO -5

Fresh snow + new artic airmass = undercut low temps.

9 minutes ago, Weather Will said:

Refresh my memory on when we should stop looking at ensembles.... I generally would stop leaning on them inside five days.

I stop relying on ensembles within 48 hours before an event.

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55 minutes ago, yoda said:

@Terpeast @MillvilleWx

Question - 12z CMC shows sleet nearby.  However, checking the column/soundings, only the 750mb to around 800mb level (maybe 825mb) goes above 0c.  EZF at 120 has it around 1C.  Is that enough to wreck snow accumulation?  The warm zone is so small that I don't think it would make a big deal?

The model very likely has a small decision tree approach when it comes to ptype dissemination, so any nose above the 0°C threshold will ultimately shift the ptype to a more mixed variety. Pending the depth of the omega between 850-600mb and the intensity of the precip, the result could still yield snowfall, albeit more clumped aggregates and lower ratios. The warm advection regime within the boundary layer will ultimately cause a changeover somewhere with the current southerly flow magnitude being progged. Climo suggests those Fredericksburg on south would have the highest potential with Southern MD likely to be next on any northerly adjustment. I think those that are along and north of Rt50 should stay all snow with this one with realistically the zone north of Fairfax/Northern Prince William/Charles counties probably maintaining most, if not all snow. Would need this storm to cut further north to threaten those zones.
 

Best accums will be within the 7H and 85H FGEN areas with the northern periphery seeing best ratios to offset the “lighter” precip potential. 85H FGEN will have slightly lower ratios, but more precip. This is a good dual maxima setup wherever this sets up. Jury still out, but I still think this ends up a Central VA on northward storm. Ensembles have been pretty insistent on that. GFS waffling on location should be a major red flag in terms of forecasting. Until other models follow suit and/or GFS becomes steadily locked in for multiple days, I don’t see its 12z representation being the final solution.   

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2 hours ago, TSSN+ said:

Good thing you’re not cause we don’t care what you think. We live here, we know what happens the majority of the time. Also still 4-5 days out. We lost storms in 3-4 days our before and seen massive shifts inside 72hrs. 

That is true for everyone. A north or south shift making some happy and some sad. Snow IS a IMBY thing.

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3 minutes ago, stormtracker said:

We're still 5 days out tho.  I'm very cautiously optimistic

Since I ain't gonna be there this is rich - but agree with the cautious optimism. Fairly narrow zone that gets the true goods - 100mi wide? The usual last-second shifts we get are gonna screw someone in this region. Most should see something, in fact if the EURO is right (and has been consistent) most do very well. But a little glad I won't be sweating the last second 50mi shift one way or the other.

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2 minutes ago, NorthArlington101 said:

Since I ain't gonna be there this is rich - but agree with the cautious optimism. Fairly narrow zone that gets the true goods - 100mi wide? The usual last-second shifts we get are gonna screw someone in this region. Most should see something, in fact if the EURO is right (and has been consistent) most do very well. But a little glad I won't be sweating the last second 50mi shift one way or the other.

Lately, the sweating part is the only thing that's a lock around here.

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1 minute ago, stormtracker said:

Lately, the sweating part is the only thing that's a lock around here.

Well it’s going to be cold enough soon so maybe our sweat will increase the qpf enough. 

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The model very likely has a small decision tree approach when it comes to ptype dissemination, so any nose above the 0°C threshold will ultimately shift the ptype to a more mixed variety. Pending the depth of the omega between 850-600mb and the intensity of the precip, the result could still yield snowfall, albeit more clumped aggregates and lower ratios. The warm advection regime within the boundary layer will ultimately cause a changeover somewhere with the current southerly flow magnitude being progged. Climo suggests those Fredericksburg on south would have the highest potential with Southern MD likely to be next on any northerly adjustment. I think those that are along and north of Rt50 should stay all snow with this one with realistically the zone north of Fairfax/Northern Prince William/Charles counties probably maintaining most, if not all snow. Would need this storm to cut further north to threaten those zones.
 
Best accums will be within the 7H and 85H FGEN areas with the northern periphery seeing best ratios to offset the “lighter” precip potential. 85H FGEN will have slightly lower ratios, but more precip. This is a good dual maxima setup wherever this sets up. Jury still out, but I still think this ends up a Central VA on northward storm. Ensembles have been pretty insistent on that. GFS waffling on location should be a major red flag in terms of forecasting. Until other models follow suit and/or GFS becomes steadily locked in for multiple days, I don’t see its 12z representation being the final solution.   

Ahh, decision trees. That’s interesting, but makes sense due to the nominal output. I vote to prune them at majority snow…for the sake of digital snow.
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