Convective Discussion
Thunderstorms are expected to form ahead of a cold front approaching from Quebec. There is potential for very heavy downpours or rain, strong winds and possible hail over northern New Brunswick this afternoon and to a lesser extent over central New Brunswick early this evening. Elsewhere some thundershower activity is either occurring or possible today in the areas highlighted. Thundershowers over Labrador are giving significant lightning and possibly gusty winds. However, these thundershowers won’t likely be severe.
Technical Discussion
There is a 250 mb Jet of 75 to 90 knots extending from the Gulf of Maine to northern NB to southern Labrador. There is a deep layer thermal ridge extending from Cape Hatteras to Newfoundland. The associated low level Jet is 20 to 30 knots. The primary triggers are sunshine and the cold front over southern Quebec. Cape values are over 1000 J/kg over the primary threat area. However, there is a cap at 750 – 800 mb that needs to broken before significant thunderstorms can form. Rainfall rates over northern NB could exceed 25mm in an hour due to the fact the airmass is very moist and steering flow is moderate around 20 to 25 knots. There could also be some training of cells due to unidirectional flow from the sfc to 500 mb.
Regional Impacts.
Primarily NB, but also Lab.
Hatt