Convective Outlook: Sun 24 Sep 2017
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sun 24 Sep 2017 - 05:59 UTC Mon 25 Sep 2017

ISSUED 17:47 UTC Sat 23 Sep 2017

ISSUED BY: Dan

Blocking pattern persists across much of Europe, with a largescale trough over the North Atlantic. On the forward-side, a slow-moving frontal zone straddling the Irish Sea will become subject to wave development as a series of shortwaves drift northwards in the mean upper flow. This will result in renewed pulses of heavy rain running along the front, with potential for some embedded convection elements - though with rather meagre instability, confidence is not particularly high on the lightning aspect and hence a broad LOW threat level has been issued.


One area of interest involves W Cornwall / W Devon into S + W Wales during the late afternoon but more especially evening hours as a pronounce zone of wind convergence is simulated by successive EURO4 runs behind the main frontal precipitation. Given very moist low-level air with dewpoints of 14-16C, and PWAT in the mid 20s mm there is scope for a line of heavy showers to develop and propagate NE-wards with time. Marginal mid-level lapse rates suggests such convection may be restricted somewhat in depth (and hence limiting the lightning potential), but a secondary LOW threat level has been issued to be considered as "MARGINAL" (15-30% chance of lightning within a 25 mile radius) which may be upgraded to a SLGT if confidence improves.

Elsewhere, in the post-frontal environment a few isolated to well-scattered showers are likely over western Ireland given closer proximity to upper trough and associated deeper instability.