Severe Thunderstorm Warning 9, NWS Caribou, ME

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CARIBOU ME
258 PM EDT TUE JUL 18 2000

SYNOPSIS:

A COLD FRONT WILL CROSS THE STATE TONIGHT ACCOMPANIED BY SHOWERS AND
THUNDERSTORMS. A SECONDARY TROF WILL THEN CROSS THE REGION
WEDNESDAY.

TECHNICAL DISCUSSION:

CURRENT SURFACE ANALYSIS INDICATED A COLD FRONT ACROSS QUEBEC
PROVINCE. THE COLD FRONT WILL CONTINUE ADVANCING EASTWARD THIS
EVENING AND CROSS THE STATE TONIGHT...EXITING THE REGION DURING THE
EARLY MORNING HOURS. A SECONDARY TROF WILL CROSS THE AREA WEDNESDAY.
HIGH PRESSURE WILL THEN RIDGE TOWARD THE REGION WEDNESDAY NIGHT AND
THURSDAY. ALOFT...THE UPPER TROF AND ASSOCIATED VORT MAX WILL LIFT
ACROSS THE REGION EARLY TONIGHT. A CLOSED UPPER LOW THEN PERSISTS
ACROSS ONTARIO/QUEBEC PROVINCES THROUGH THURSDAY MAINTAINING A
CYCLONIC FLOW ACROSS THE REGION.

KCBW AND REGIONAL RADARS CONTINUE TO INDICATE SHOWERS AND
THUNDERSTORMS DEVELOPING IN ADVANCE OF THE APPROACHING COLD FRONT.
THE SHOWER/THUNDERSTORM ACTIVITY IS ALSO BEING SUPPORTED BY UPPER
LEVEL DIVERGENCE IN THE LEFT EXIT REGION OF A JET MAX CROSSING NEW
ENGLAND AND COOLING ALOFT ASSOCIATED WITH THE MID/UPPER LEVEL TROF.
JET SUPPORT WILL CONTINUE THROUGH THE EVENING HOURS BEFORE
DIMINISHING DURING THE EARLY MORNING. MOISTURE WILL ALSO CONTINUE TO
POOL ACROSS THE REGION IN ADVANCE OF THE FRONT DURING THE EVENING.
EXPECT SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS THE REGION
UNTIL THE FRONTAL PASSAGE. SOME DIURNAL HEATING COULD ALSO BE A
CONTRIBUTING FACTOR DURING THE NEXT FEW HOURS. LIFTED INDICES OF
AROUND -3 AND CAPES OF AROUND 1500 J/KG WILL PERSIST THROUGH THE
EARLY EVENING. THE POTENTIAL FOR A FEW SEVERE THUNDERSTORMS WILL ALSO
PERSIST THROUGH THE EVENING. SATELLITE IMAGERY SHOWS EXTENSIVE POST
FRONTAL CLOUD COVER WHICH SHOULD OVERSPREAD THE REGION LATER TONIGHT
IN THE WAKE OF THE FRONT.

EXPECT EXTENSIVE POST FRONTAL CLOUDINESS WILL PERSIST ACROSS THE
NORTH AND MOUNTAINS WEDNESDAY...WITH ANY SUN TRIGGERING THE
DEVELOPMENT OF INSTABILITY CU/SC. CYCLONIC FLOW...THE PASSAGE OF A
SURFACE TROF AND DIURNAL INSTABILITY COULD ALSO HELP TRIGGER A FEW
AFTERNOON SHOWERS ACROSS THE NORTH AND MOUNTAINS. DOWNSLOPING WINDS
SHOULD HELP MIXING ACROSS DOWNEAST AREAS AND EXPECT PARTLY SUNNY
SKIES THERE WEDNESDAY. BREEZY CONDITIONS WILL OCCUR REGIONWIDE.

EXPECT PARTLY CLOUDY SKIES REGIONWIDE WEDNESDAY NIGHT WITH
SEASONABLY COOL CONDITIONS.

LOW PRESSURE WILL TRACK OFFSHORE OF THE NEW ENGLAND COAST THURSDAY.
AT THE MOMENT...IT APPEARS THE DEEPER MOISTURE AND BETTER LIFT
ASSOCIATED WITH THIS SYSTEM WILL REMAIN SOUTHEAST OF THE REGION.
EXPECT PARTLY SUNNY SKIES REGIONWIDE THURSDAY WITH DIURNAL CU/SC
ACROSS THE NORTH WHILE DOWNEAST AREAS ARE CLIPPED BY SOME CLOUDS
ASSOCAITED WITH THE EDGE OF THE COASTAL LOWS CLOUD SHIELD.

COASTAL WATERS:

AREAS OF FOG WILL CONTINUE TO REDUCE VISIBILITIES UNTIL THE FRONTAL
PASSAGE WHEN DRIER AIR WILL OVERSPREAD THE WATERS. SHOWERS AND
THUNDERSTORMS WILL ALSO CONTINUE UNTIL THE FRONTAL PASSAGE. WINDS AND
SEAS WILL BE LOCALLY HIGHER AROUND THUNDERSTORMS. WINDS COULD
APPROACH MARGINAL SMALL CRAFT ADVISORY LEVELS THURSDAY...BEFORE
DIMINISHING LATE.

EXTENDED:

AN UPPER LOW WILL EXIT THE MARITIME PROVINCES LATE THIS WEEK.
HOWEVER...ANOTHER UPPER LOW WILL DROP TOWARD NEW ENGLAND DURING THE
WEEKEND AS A DISTURBANCE LIFTS ALONG THE COAST. UNSETTLED WEATHER
WILL AGAIN RETURN TO THE REGION DURING THE WEEKEND WITH A CHANCE OF
RAIN AND SHOWERS.

BGR BB 059/074 050/075 051 03700 333/332/00/10
CAR EB 055/067 046/067 046 03731 333/433/00/10

.CAR...NONE.

NORCROSS