I've seen another one of the leading models do something similar (850s were closer to 3 or 4 IIRC) in the past. I flagged it up with the agency concerned but never really got to the bottom of it.
It is theoretically possible of course. If the temp maxes out at 850hpa and the freezing layer is say only 30mb thick, then you'd get snow from that. And while 3-4C is very very extreme, I think it does occasionally happen in the US (strong warm front coming into cold air combined with some orographic jiggery pokery).
For this event, I don't think snow will be falling at those T850s but the surface warm front decoupling from the upper front combined with decreasing wind/evap cooling could produce +ve T850 snow, in 2010 I saw snow at +1C so it does happen even here.
The bigger worry is that when you see snow falling at positive T850s that also probably means a significant freezing rain band. I'm suprised the metoffice haven't mentioned it.
EDIT: I should add that all the high res models that are in range (except the UKV) are producing positive T850 snow, so it isn't just one model. Unfortunately the met does seem to have a bias towards their own model, if the UKV was showing this then there would definitely be a freezing rain mention.
Edited by user
06 February 2024 08:09:52
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Reason: Not specified
Twitter: @QuantumOverlord (general), @MedicaneWatch (medicane/TC stuff)
2023/2024 Snow days (approx 850hpa temp):
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
Total: 8 days with snow/sleet falling.
2022/2023 Snow days (approx 850hpa temp):
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
Total: 7 days with snow/sleet falling.
2021/2022 Snow days (approx 850hpa temp):
26/11 (-5), 27/11 (-7), 28/11 (-6), 02/12 (-6), 06/01 (-5), 07/01 (-6), 06/02 (-5), 19/02 (-5), 24/02 (-7), 30/03 (-7), 31/03 (-8), 01/04 (-8)
Total: 12 days with snow/sleet falling.