240  
FXCN01 CWHF 170804  
 
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  
THURSDAY 17 JULY  
 
===================================================================  
KEY FORECAST POINTS:  
 
- WITH A MOIST SOUTHERLY FLOW, EXPECT LOW CONDITIONS TO REMAIN OVER  
THE REGION TODAY.  
- AN APPROACHING LOW PRESSURE SYSTEM WILL GIVE PATCHY DRIZZLE, A FEW  
SHOWERS AND THE RISK OF THUNDERSHOWERS TO THE REGION BEGINNING  
OVERNIGHT INTO FRIDAY.  
- CONDITIONS IMPROVE AND DRYER AIR MOVES INTO THE REGION IN THE WAKE  
OF THE COLD FRONT FRIDAY AFTERNOON.  
- DEVELOPING TROUGHING TO THE WEST WILL SPREAD CLOUD AND SHOWERS  
INTO THE REGION SUNDAY AND WILL BE SLOW TO DEPART MONDAY.  
 
===================================================================  
SHORT RANGE DISCUSSION FOR 0600Z 17 JULY TO 0300Z 19 JULY.  
MODEL DISCUSSION: USED RDPS.  
CONFIDENCE: GENERALLY HIGH.  
COMMENTS/IMPACTS: AS WEAK RIDGING MOVES OFF TO THE EAST, EXTENSIVE  
MIST FOG AND STRATUS HAVE DEVELOPED IN THE MOIST AIRMASS OVER MUCH  
OF NOVA SCOTIA OVERNIGHT. EXPECT THE STRONG SUN TO BURN OFF A  
CONSIDERABLE AMOUNT OF STRATUS/MIST/FOG OVER LAND TODAY. HOWEVER,  
THE CONTINUED SOUTH/SOUTHWEST FLOW INTO THE HALIFAX REGION WILL  
KEEP THE STRATUS CLOUD MOVING INLAND FROM THE EXTENSIVE AREA OF  
STRATUS OVER THE ATLANTIC WATERS. REGARDLESS, SUNNY BREAKS ARE  
POSSIBLE THIS AFTERNOON OVER THE BASIN REGION, THOUGH NOT LIKELY  
MUCH FURTHER SOUTH.  
OVERNIGHT, THE CLOUD WILL THICKEN UP AND PATCHY DRIZZLE WILL  
DEVELOP AS WELL AS THE EXTENSIVE MIST AND FOG OVER THE APPROACHES  
WILL MOVE INLAND. A FEW SHOWERS WITH THE RISK OF THUNDERSHOWERS  
WILL ALSO MOVE INTO THE REGION WELL AHEAD OF AN APPROACHING COLD  
FRONTAL TROUGH OVERNIGHT. THESE SHOWERS/RISK OF THUNDERSHOWERS WILL  
CONTINUE INTO FRIDAY MORNING. EXPECT CONDITIONS TO IMPROVE/CLEAR IN  
THE WAKE OF THE COLD FRONT FRIDAY AFTERNOON.  
WINDS.. MODERATE TO STRONG SOUTHERLY WINDS WILL DEVELOP OVER THE  
APPROACHES WELL AHEAD OF THE COLD FRONT TONIGHT THEN VEER TO  
MODERATE NORTHWEST IN THE WAKE OF THE COLD FRONT FRIDAY AFTERNOON.  
 
LONG RANGE DISCUSSION FOR 0300Z 19 JULY TO 0300Z 22 JULY.  
MODEL DISCUSSION: USED RDPS/GDPS.  
CONFIDENCE: GENERALLY HIGH.  
COMMENTS/IMPACTS: RIDGING WILL GIVE A MAINLY SUNNY DAY SATURDAY  
THOUGH SOME CIRRUS MAY BEGIN TO MOVE INTO THE REGION LATE IN THE  
DAY. A TROUGH BEINGS TO DEVELOP/ORGANIZE EAST OF THE APPALACHIANS  
EARLY SUNDAY GIVING CLOUD TO THE REGION AND DEVELOPING SHOWERS.  
GDPS NOW BRINGS THE LINE OF SHOWERS INTO THE REGION FASTER THAN THE  
GDPS.. THOUGH LIKELY TO BE AN AFTERNOON START TIME. THE TROUGH,  
WITH DEVELOPING LOWS EMBEDDED, WILL MOVE THROUGH THE REGION  
OVERNIGHT GIVING CONTINUED SHOWERS AND LIE OVER OR JUST EAST BY  
MONDAY MORNING. SHOWERS ARE EXPECTED TO BE ENDING MONDAY MORNING  
THOUGH AN UNSTABLE AIRMASS LEFT IN ITS WAKE WILL GIVE A CONTINUED  
CHANCE OF SHOWERS THROUGH THE AFTERNOON. CLOUDY CONDITIONS IN THE  
MORNING WILL BECOME A MIX OF SUN AND CLOUD BY AFTERNOON BEFORE  
CLEARING IN THE EVENING.  
 
END/METOC-HFX  
 
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