Forecaster: Stephen Déry
Synoptic overview: There is no major system affecting the Rockies this morning with a weak high pressure system (1021 hPa) residing over Jasper National Park and a weak low pressure system (1015 hPa) in southern BC. The main synoptic feature that affected the Rockies over the past couple of days has shifted very slowly eastward and the low pressure centre (1002 hPa) currently lies on the Saskatchewan/Montana border. It is a vertically stacked low pressure with corresponding upper level lows at 500 and even 250 hPa, suggesting the low is no longer intensifying and will continue a slow progress northeastward. The flow aloft will be from the north and will advect cold air in the mid-levels of the atmosphere leading to instability as the surface gradually warms today. In the short- to medium-term an elongated upper level trough will continue to influence our study area inducing possible weak convection later in the day.
GEM2.5 Partly cloudy conditions with a slight (40%) chance of showers today mainly in the afternoon with the risk of a thunderstorm around 4 pm. The model suggests an accumulation of 5.6 mm over one hour, perhaps due to a passing storm (CAPE values ~800 J/kg). Temperatures will warm to 18°C by the afternoon. Clearing thereafter and possibility of scattered showers on Sunday with total accumulation of ~1.5 mm.
GEM10 predicts similar conditions but with more abundant precipitation starting around 1 am MDT on Sunday for a total daily accumulation of 10 mm with precipitation ending near 3 pm.
HRRR minimal precipitation today 1.3 mm starting at 1 pm
NAM resembles GEM10 with overnight precipitation totaling ~10 mm.
GEM2.5 Convective instability will affect Fortress today with scattered showers starting around noon. Total precipitation during the day is ~4 mm in liquid form. Temperatures will peak at ~12°C. Similar conditions will prevail on Sunday with possibly another 4 mm or precipitation around 3 pm.
GEM10 Minimal precipitation today ~1 mm with slightly higher amount Sunday starting around noon (4 mm).
HRRR is dry at Fortress for this forecast cycle.
NAM is wet, suggests precipitation starting ~8 pm Saturday until noon Sunday with total accumulation 13 mm (all liquid).
Storm Mountain Lodge
GEM2.5 Similar conditions to the other sites with clouds and convective precipitation starting mid-day with total accumulation (all liquid) of 2 mm both today and tomorrow. Maximum temperature will reach 20°C.