453
FXCN01 CWHF 230806
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 0830Z ON
SUNDAY 23 AUG
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KEY FORECAST POINTS:
- MOIST UNSTABLE AIRMASS GIVING LOW CONDITIONS IN SHOWERS, AT TIMES
HEAVY AND A RISK OF THUNDERSTORMS.
- CONDITIONS IMPROVE MONDAY NIGHT.
- BROAD TROUGHING AND DAYTIME HEATING GIVING A CHANCE OF
SHOWERS/RISK OF THUNDERSTORMS TUESDAY/WEDNESDAY.
- WEAK RIDGING KEEPING THINGS MORE STABLE THURSDAY.
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SHORT RANGE DISCUSSION FOR 0600Z 23 AUG TO 0300Z 25 AUG.
MODEL DISCUSSION: USED RDPS/HRDPS.
CONFIDENCE: HIGH FOR GENERAL CONDITIONS. MEDIUM FOR TIMINGS OF
HEAVIER PRECIPITATION AND RAINFALL AMOUNTS.
COMMENTS/IMPACTS: ANCHORING LOW OVER THE GREAT LAKES REGION GIVING A
MOIST AND UNSTABLE SOUTHERLY FLOW TO THE REGION. A FRONTAL WAVE IS
DEVELOPING EARLY THIS MORNING AND WILL TRACK ACROSS THE REGION
TODAY GIVING SHOWERS AT TIMES HEAVY WITH A RISK OF THUNDERSTORMS
TODAY INTO TONIGHT. EXPECT LOW CLOUD AND EXTENSIVE MIST WITH PATCHY
FOG TODAY IN A MODERATE TO STRONG SOUTHEAST FLOW. HEAVY SHOWERS
TAPER TO DRIZZLE AND A FEW SHOWERS OVERNIGHT IN THE WAKE OF THE
FRONTAL TROUGH MOVING THROUGH. A SECOND IMPULSE WILL AFFECT THE
REGION.. RDPS KEEPS IT MOSTLY OFF THE COAST WHILE THE HRDPS TRACKS
IT THROUGH THE LOCAL REGION.. GIVING POTENTIALLY HEAVY SHOWERS/RISK
OF THUNDERSTORMS MONDAY MORNING/EARLY AFTERNOON BEFORE TAPERING
ONCE AGAIN TO PATCHY DRIZZLE/SHOWERS. FINALLY MONDAY NIGHT.. THE
MOIST AND UNSTABLE SOUTHERLY FLOW MOVES EAST OF THE LOCAL REGION
GIVING SOMEWHAT IMPROVING CONDITIONS LATE OVERNIGHT. WINDS WILL
VEER TO THE SOUTH THIS EVENING THEN WEAKEN SOMEWHAT OVERNIGHT AND
SHIFT TO THE SOUTHWEST BEFORE INCREASING ONCE AGAIN AHEAD OF THE
NEXT IMPULSE MONDAY... THEN BECOMING LIGHT MONDAY NIGHT.
RAINFALL.. AS OF 0400 LOCAL TIME, 10 TO 15 MM OF RAIN HAS FALLEN
ACROSS THE REGION. AN ADDITIONAL 30 TO 60 MM IS EXPECTED THOUGH MAY
VARY WIDELY PENDING WHERE THE HEAVIEST SHOWERS TRACK THROUGH.
REGIONAL MODEL INDICATES HEAVIES SHOWERS WILL OCCUR THIS MORNING
AND THEN ONCE AGAIN THIS EVENING.
LONG RANGE DISCUSSION FOR 0300Z 25 AUG TO 0300Z 28 AUG.
MODEL DISCUSSION: USED RDPS/GDPS.
CONFIDENCE: GENERALLY HIGH.
COMMENTS/IMPACTS: AS THE ANCHORING LOW WEAKENS AND TRACKS UP INTO
QUEBEC/LABRADOR, AS NOTED ABOVE, THE MOIST AND UNSTABLE SOUTHERLY
FLOW STREAKING ACROSS THE REGION MOVES OFF TO THE EAST AND
EXPECTED A CLEARING TREND TUESDAY MORNING. AS BROAD TROUGHING
EXTENDS SOUTHWARDS FROM THE LOW, EXPECT DAYTIME HEATING TO COMBINE
WITH THE UNSTABLE AIRMASS TO GIVE A CHANCE OF SHOWERS/RISK OF
THUNDERSTORMS TUESDAY AND WEDNESDAY AFTERNOON. RDPS/GDPS TRACK THE
BASE OF THE TROUGH THROUGH WEDNESDAY, GIVING A BETTER CHANCE OF
CONVECTION TO THE REGION COMPARED TO TUESDAY. BY THURSDAY.. WEAK
RIDGING WILL STABILIZE THE AIRMASS SOMEWHAT AND A MIX OF SUN AND
CLOUD IS EXPECTED. POSSIBLY MORE CLOUD THAN SUN IN THE AFTERNOON AS
GDPS SHOWS AND AREA OF MID/HIGH CLOUD MOVING OVER THE RIDGE...
THOUGH FOR NOW, A MIX IF FORECAST.
END/METOC-HFX
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