Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

NB: None

NS: None

PEI: None

NF&Lab: None

Marine waters: Isolated thunderstorms developing tonight over southwestern waters, then spreading northeast.

 

Convective Discussion

The main features this morning are a 500mb upper low south of New England with a southeasterly upper jet ahead of it as indicated by Yarmouth and Shearwater soundings. At the surface, a frontal boundary extend from the back of the upper low, mid-Atlantic coast of the US, to southern Quebec, and then to Labrador. Several low pressure centres are analysed along the front, but the main centre appears to be just north of the Ottawa Valley where several clusters of lightning strikes are detected . Another area with lightning activity is over the Gulf Stream, southeast of Nantucket. Over time, a push of cold air aloft currently over James Bay will catch up with the frontal band over northern Quebec and Lab, while a new upper low emerges over the Maritimes. This new system will drive a swath of very moist air over all of the Atlantic provinces which will eventually connect with the advancing frontal boundary producing some heavy rain. Isolated thunderstorms will likely occur near the upper low, and along the front.

 

 

Thunderstorm Outlook for Friday

 

Isolated thunderstorms ahead of an upper low over CB and southwestern NF, and along a frontal system advancing over Labrador.

 

 

Convective Outlook Valid for Today, Tomorrow and Friday

Regional Impacts

NB: None

NS: None

PEI: None

NF: None

Labrador: Isolated thunderstorms possible over northwestern sections later today into this evening.

Marine waters: Isolated thunderstorms for Laurentian Fan and East Scotian Slope by later today into this evening.

 

Convective Discussion: Two areas of focus for convection today. The primary area of concern will be over northwestern Labrador where surface based convection initiating in north-central Quebec will move eastward towards a QS upper ridge positioned over central Labrador. Any convection will become elevated and more isolated as it moves towards this region, as upper level dynamics become less favourable. Nevertheless an isolated strike cannot be ruled out entirely with marginal MUCAPES of ~200 J/kg. The second area of convection will be located to the east of a cut-off low over the eastern slope waters. Here convection is expected to be elevated forced by decent instability  (MUCAPES ~500 J/Kg), and a strong LLJ (~30-35 kts at 850 mb). However it should be isolated in nature given that the best synoptic ascent will be located well to the SW (near the cut-off low). Over the next two days this area of concern is expected to gradually advect west-northwest, and convection should increase in frequency from isolated to scattered as PVA becomes more aligned with the area of instability and the LLJ. Continued moisture advection to the from the subtropics will cause PWATs to rise into the mid 40s by Thursday evening, so if elevated convection does manage to make it to land, rainfall rates will become a primary hazard.

 

Thunderstorm outlook for today:

 

 

Thunderstorm outlook for tonight:

 

 

Thunderstorm outlook for Thursday:

 

 

Thunderstorm outlook for Thursday night into Friday:

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

NB: None

NS: None

PEI: None

NF: None

Labrador: None, isolated thunderstorms possible over northwestern sections on Wednesday.

Marine waters: Isolated Thunderstorms over southwestern Grand Banks. Isolated thunderstorms for Laurentian Fan and East Scotian Slope by Wednesday evening into Thursday.

 

Convective Discussion: Upper trough in the process of being cut-off to the south of the Maritimes as heights rise in Labrador. To the east of this feature moist unstable profiles and a moderately strong 850 mb jet can support isolated elevated convection over the southwestern Grand Banks.

As this cut-off feature retrogrades to the southwest, the instability associated with this jet structure will gradually advect westward allowing for isolated convection over Laurentian fan and the East Scotia Slope on Wednesday night into Thursday respectively. On Wednesday afternoon northwestern most Labrador has profiles that support elevated instability on the order of 300-500 J/kg however a sufficient triggering mechanism may be lacking as a warm front remains well to the east over north-central Quebec. Regardless an isolated strike cannot be ruled out, especially if this feature advects eastward faster than advertised by our current guidance.  

 

Thunderstorm outlook for today:

 

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Wednesday:

 

 

Thunderstorm outlook for Wednesday Night and Thursday:

 

 

TEST

Thunderstorm Outlook for Day 1

 

Regional Impacts

 

Convective Discussion

 

Thunderstorm Outlook for Day 2

Atlantic Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today, June 20^th.

 

Regional Impacts

Isolated non-severe thundershowers are possible over the Gulf waters as well as offshore over Laurentian fan. These cells are expected to be embedded in showers being driven by the upper trof. Only a few lightning strikes are forecast in the risk areas.

 

Convective Discussion

The upper low is still the dominant weather forcing for today. Not much has changed since yesterday, other than sfc temperatures cooling further in NB. As a result, the atmosphere although saturated/moisture rich in the low levels is fairly stable. Shearwater this AM is moist yet stable up to 9,000ft. Much more of a springtime fog/drizzle airmass regime than a summer severe weather day. East of CYQY, there is even thermal ridging above 700 to prevent anything further. And, back to the west, the airmass is far too dry (across Maine).

 

 

Thunderstorm Outlook for Tomorrow, June 21^st.

 

Regional Impacts

No thunderstorms expected at this time.

 

Convective Discussion

Atmosphere continues to stabilize further as upper low fills. Forecast highs quite cool across Atlantic Canada for first day of summer.

 

 

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END/ASPC