203
FXCN01 CWHF 302000
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
SUNDAY 30 AUG
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KEY FORECAST POINTS:
- FAST MOVING TROUGH GIVING SHOWERS/RISK OF THUNDERSTORMS TONIGHT
- CLEARING EARLY MONDAY THEN FAIR WEATHER INTO WEDNESDAY.
- WHILE STILL UNCERTAIN, MODELS NOW LEANING TOWARDS RIDGING MOVING
EAST ALLOWING LOW PRESSURE SYSTEM TO BRING SHOWERS TO THE REGION
THURSDAY.
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SHORT RANGE DISCUSSION FOR 1800Z 30 AUG TO 0300Z 01 SEP.
MODEL DISCUSSION: USED RDPS/HRDPS.
CONFIDENCE: GENERALLY HIGH.
COMMENTS/IMPACTS: MODERATE TO STRONG SOUTHWEST WINDS WILL EASE AS
A TROUGH APPROACHES FROM THE NORTHWEST THIS EVENING. CLOUD WILL
INCREASE EARLY THIS EVENING WITH SHOWERS DEVELOPING LATER THIS
EVENING AND A RISK OF THUNDERSTORMS OVERNIGHT. SHOWERS END NEAR
DAWN THEN SKIES CLEAR MONDAY MORNING IN THE WAKE OF THE TROUGH AND
AS RIDGING BUILDS IN FROM THE WEST. WINDS WILL VEER TO THE
NORTHWEST WITH GUSTS IN THE LOW 20 KNOTS RANGE BY MONDAY MORNING.
THERE IS A SLIGHT CHANCE OF GUSTS TO 25 KNOTS OVER 12 WING
SHEARWATER AND AN ADVISORY MAY BE REQUIRED. LATE IN THE DAY/EVENING
MONDAY.. LINGERING CLOUD FROM A WEAKENED TROUGH AND ENHANCED BY THE
COOLER AIRMASS MOVING OVER THE WARMER GULF OF ST.LAWRENCE WATER
WILL MOVE ACROSS NOVA SCOTIA. CLOUD HEIGHTS ARE EXPECTED TO REMAIN
AROUND 4000 FEET.
LONG RANGE DISCUSSION FOR 0300Z 01 SEP TO 0300Z 04 SEP.
MODEL DISCUSSION: USED RDPS/GDPS.
CONFIDENCE: GENERALLY HIGH TUESDAY/WEDNESDAY THEN LOWER FOR THURSDAY.
COMMENTS/IMPACTS: AS NOTED ABOVE.. LINGERING CLOUD FROM A WEAKENED
TROUGH WILL MOVE ACROSS THE PROVINCE MONDAY NIGHT AND OFF THE COAST
TUESDAY MORNING. EXPECT A BIT OF CU TO DEVELOP TUESDAY AFTERNOON
AND SOME HIGH CLOUD SPILLING INTO THE RIDGE AS IT TRACKS THROUGH
THE REGION. WITH THE RIDGE AXIS TO THE EAST OF THE REGION
WEDNESDAY, EXPECT SOME CU TO DEVELOP IN EASTERLY FLOW OVER THE
WARMER WATERS AND MOVE ACROSS THE PROVINCE. AT THE SAME TIME,
ESPECIALLY IN THE EVENING AND OVERNIGHT, MID AND HIGH CLOUD WILL
MOVE INTO THE REGION AHEAD OF A REORGANIZING LOW PRESSURE SYSTEM.
PREVIOUS MODEL RUNS HAS THE RIDGE LINE STALLED JUST TO THE EAST,
KEEPING MOST OF THE CLOUD AND PRECIPITATION WELL TO THE WEST. THE
LATEST GUIDANCE FROM GDPS/GFS/ECMWF/ICON ALL BRING CLOUD AND
SHOWERS INTO THE REGION THURSDAY, AS WELL AS STRONGER SOUTHEAST
WINDS AHEAD OF THE LOW. HAVE CHANGED THE FORECAST TO REFLECT THE
AGREEMENT OF SHOWERS/RAIN MOVING INTO THE REGION ON THURSDAY. AT
THIS TIME, THE UKMET STILL SUPPORTS A STRONGER/STALLED RIDGE
KEEPING DRYER AIR OVER THE REGION BUT SEEMS AN OUTLIER. THAT SAID..
OVER THE PAST FEW DAYS, NUMEROUS MODELS HAVE SHIFTED BACK AND
FORTH BETWEEN STALLING THE RIDGE/DRY AIR OVER NOVA SCOTIA OR
ALLOWING THE RIDGE TO MOVE EASTWARDS AND THE REDEVELOPING LOW TO
GRADUALLY TRACK INTO THE REGION THURSDAY. UNCERTAINTY REMAINS WITH
THIS SYSTEM THOUGH MODEL AGREEMENT HAS TRENDED TOWARDS THE SYSTEM
MOVING INTO THE HALIFAX REGION ON THURSDAY WITH STRONG SOUTHEAST
WINDS ASSOCIATED.
END/METOC-HFX
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