794
FXCN01 CWHF 192012
FORECAST DISCUSSION FOR OPS AREA ALPHA AND THE ECHOES, CFB HALIFAX
PROPERTIES AND 12 WING SHEARWATER ISSUED BY AVIATION AND DEFENCE
SERVICES OF ENVIRONMENT AND CLIMATE CHANGE CANADA AT 2030Z ON
THURSDAY 19 JUNE
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KEY FORECAST POINTS:
- MOIST SOUTHERLY FLOW CONTINUES TO GIVE STRATUS, DRIZZLE, MIST AND
FOG TONIGHT AND INTO FRIDAY MORNING.
- STRONGER SOUTHWEST WINDS DEVELOP FRIDAY, IMPROVING VISIBILITIES
AND CEILINGS IN AND AROUND THE HARBOUR.
- CLEARING.. AT LEAST PARTIAL.. SLATED TO BEGIN FRIDAY EVENING.
- SUNDAY IS A TRICKY FORECAST DAY.
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SHORT RANGE DISCUSSION FOR 1800Z 19 JUNE TO 0300Z 21 JUNE.
MODEL DISCUSSION: USED RDPS
CONFIDENCE: MEDIUM-HIGH
COMMENTS/IMPACTS: THE MOIST SOUTHERLY AHEAD OF AN APPROACHING
FRONTAL TROUGH FROM ONTARIO AND QUEBEC WILL CONTINUE TO BLANKET THE
OPS AREA IN STRATUS, MIST, FOG AND PATCHY DRIZZLE. THE EXPECTED
CONVECTION HAS NOT MATERIALIZED UP TO FORECAST ISSUE TIME BUT THERE
IS STILL A REASONABLE SHOT AT GETTING AT LEAST ACC SHOWERS INTO THE
AREA THIS EVENING. WE LOSE THE MID LEVEL MOISTURE TONIGHT, AND THAT
SHOULD CUT THE RISK OF SHOWERS.
ON FRIDAY, AS THE FRONTAL TROUGH NEARS THE MARITIMES,
THE SOUTHWEST GRADIENT AHEAD OF IT TIGHTENS SIGNIFICANTLY. WINDS
ABOVE THE MARINE BOUNDARY LAYER ARE FORECAST TO BE IN THE 30-35
KNOT RANGE, BUT RIGHT AT THE SURFACE IS REMAINS SO STABLE. GUSTS
ABOVE 33 KNOTS ARE NOT FORECAST AT THIS TIME, BUT SOME AREAS ARE
LIKELY TO APPROACH 30 KNOTS DURING THE AFTERNOON. THERE'S ONLY
PATCHES OF MID LEVEL MOISTURE DURING THE DAY AHEAD OF THE TROUGH SO
ONLY A CHANCE OF SHOWERS ARE EXPECTED AT THIS TIME. STRATUS, FOG,
DRIZZLE AND MIST SHOULD ERODE FROM THE HARBOUR AND BASIN IN THE
MORNING, THEN SHOULD BECOME PATCHY IN THE AFTERNOON OVER THE
APPROACHES. AS DRIER AIR APPROACHES IN THE EVENING, THE VISIBILITY
SHOULD IMPROVE TO 6 PLUS, AND SKIES COULD START TO BREAK OPEN.
LONG RANGE DISCUSSION FOR 0300Z 21 JUNE TO 0300Z 24 JUNE.
MODEL DISCUSSION: USED GDPS
CONFIDENCE: HIGH ON SATURDAY DROPPING TO MEDIUM AT BEST FOR SUNDAY.
COMMENTS/IMPACTS: ON SATURDAY THE NORTHWEST FLOW CONTINUES INTO THE
MORNING ON SATURDAY AS THE LOW PRESSURE SYSTEM AND FRONTAL TROUGH
MOVES AWAY FROM THE MARITIMES AND ALLOW A RIDGE OF HIGH PRESSURE TO
BUILD IN. THE MODELS INSIST A SOUTHWEST FLOW WILL DEVELOP OVER THE
APPROACHES SATURDAY AFTERNOON SETTING UP A POSSIBLE CONVERGENCE
AREA NEAR THE HARBOUR SATURDAY AFTERNOON. THIS WILL KEEP THE MIX OF
SUN AND CLOUD IN THE FORECAST.
SUNDAY BECOMES THE TRICKIEST DAY TO FORECAST. A RAPIDLY MOVING
CLIPPER OUT OF ONTARIO CONTINUES TO RACE TOWARD TO MARITIMES WITH
A LARGE, BUT WEAKENING AREA OF SHOWERS. THE GDPS IS PUSHING THE
PRECIP THE FURTHEST EAST INTO HALIFAX AND HAS BEEN CONSISTENTLY
DOING SO. THE GFS DOESN'T PUT SHOWERS INTO NOVA SCOTIA AT ALL. THE
ECMWF PUTS PRECIP OVER SOUTHWESTERN NOVA SCOTIA. THIS IS TOO RISKY
TO NOT AT LEAST PUT A CHANCE IN OUR FORECAST NOW.
ON MONDAY, AS A RESULT OF THE MOISTURE MOVING ACROSS SOUTHWESTERN
NOVA SCOTIA SUNDAY NIGHT, THE MODELS ARE DETECTING A LARGE STRATUS
AND FOG DECK TO FORM OVERNIGHT AND THAT BLANKETS THE OPS AREA ON
MONDAY. OTHERWISE HOT AND HUMID WEATHER STARTS TO ENVELOP THE
MARITIMES FOR THE BEGINNING OF THE WEEK.
END/METOC-HFX
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