537
FXCN01 CWHF 030810
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
MONDAY 03 AUG
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KEY FORECAST POINTS:
- CLOUDY TODAY WITH INCREASING LIKELIHOOD OF SHOWERS
- SHOWERS AND RISK OF THUNDERBANGERS TONIGHT
- CLEARING AND WINDY ON TUESDAY
- SOME HEAT AND SOME SUN FOR THE MIDDLE OF THE WEEK.
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SHORT RANGE DISCUSSION FOR 0600Z 03 AUG TO 0300Z 05 AUG.
MODEL DISCUSSION: USED HRDPS
CONFIDENCE: MEDIUM-HIGH
COMMENTS/IMPACTS: AN AREA OF LOW PRESSURE IS FORECAST TO TRACK INTO
QUEBEC TODAY WITH A BROAD TROUGH OF LOW PRESSURE MOVING INTO NEW
ENGLAND. MOISTENING CONDITIONS ARE FORECAST FOR HALIFAX TODAY AS
THE TROUGH EDGES CLOSER. THE STRATUS SHOULD BECOME THICK ENOUGH TO
GIVE PATCHY DRIZZLE TODAY. AS THE MID AND UPPER LEVELS MOISTEN AND
BECOME UNSTABLE, SHOWERS ARE EXPECTED TO DEVELOP TODAY AS WELL,
WELL AHEAD OF THE TROUGH. THERE WILL BE A RISK OF THUNDERSHOWERS
BUT FOR TODAY, IT SEEMS THE HIGHER RISK WILL BE CLOSER TO THE BAY
OF FUNDY. THE BOUNDARY LAYER WIND IS FORECAST TO INCREASE AS WELL,
REACHING 20 KNOTS THIS AFTERNOON.
TONIGHT, THE TROUGH IS EXPECTED TO REACH WESTERN NOVA SCOTIA
OVERNIGHT. SHOWERS ACTIVITY SHOULD CONTINUE TO INCREASE. THE
BOUNDARY LAYER WIND IS ALSO FORECAST TO CONTINUE TO INCREASE,
REACHING 30 TO POSSIBLY 35 KNOTS BEFORE MORNING, ESPECIALLY IN
HEAVIER PRECIPITATION AND OVER THE APPROACHES. THE MID AND UPPER
LEVELS WILL BECOME MORE UNSTABLE AS WELL SUPPORTING THE RISK OF
THUNDERSHOWERS.
ON TUESDAY, THE TROUGH MOVES THROUGH IN THE MORNING AND WINDS WILL
SHIFT TO SOUTHWEST THEN WEST AS DRIER AIR MOVES INTO THE REGION.
THE REGIONAL AND HI RES MODELS DIFFER IN TIMING OF CLEARING
CONDITIONS FOR HALIFAX. THE HIRES IS FASTER WITH CLEARING FORECAST
BEFORE NOON. THE RDPS WAITS UNTIL MID TO LATE AFTERNOON. THE SOONER
IT CLEARS THE HIGHER THE PROBABILITY THAT WIND GUSTS REACH 35
KNOTS AS THE LOW LEVELS BECOME UNSTABLE.
LONG RANGE DISCUSSION FOR 0300Z 05 AUG TO 0300Z 08 AUG.
MODEL DISCUSSION: USED GDPS
CONFIDENCE: MEDIUM-HIGH
COMMENTS/IMPACTS: LIKE THE PREVIOUS SHIFTS, I WILL CONTINUE TO
REJECT THE GFS SOLUTION. THE ECMWF SUPPORTS THE CANADIAN SOLUTION
SO WE WILL LEAVE THE GFS AS THE OUTLIER.
DURING THE LONG RANGE PERIOD A RIDGE OF HIGH PRESSURE SETS UP
SOUTH OF NOVA SCOTIA AND KEEPS A WESTERLY FLOW OF DRIER AIR OVER
THE REGION. MODELS ARE SHOWING INLAND TEMPERATURES PUSHING OVER 30C
EACH DAY AND WITH THE FLOW MOSTLY WESTERLY WE SHOULD BE ABLE TO GET
SOME OF THAT HEAT INTO THE DOCKYARD AS WELL. THE STRONGEST
SUPPORTING SIGNAL FOR 30C IS ON WEDNESDAY AS THE LOW LEVEL WIND
STAY MOSTLY WESTERLY ALL DAY (EXCEPT IN THE APPROACHES). BY
THURSDAY THAT WEST FLOW IS LIGHTER AND SOME SEABREEZE COMPONENT IS
BOUND TO REDUCE THE SURFACE TEMPERATURE A BIT.
IF THE GFS IS CORRECT HOWEVER, MOISTURE FROM NEW ENGLAND WILL
STREAM OVER NOVA SCOTIA ON THURSDAY AND IT COULD BE QUITE CLOUDY..
AND PRECIP CANNOT BE RULED OUT. NOTHING SUPPORTS THAT SOLUTION AT
THIS TIME HOWEVER.
END/METOC-HFX
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