Severe Thunderstorm Warning 19, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
335 PM EDT FRI JUN 14 2002

SCATTERED TO NUMEROUS SHOWERS WILL CONTINUE INTO THE EVENING HOURS
AS DIURNAL HEATING COMBINES WITH THE UPPER COLD POOL THAT IS
ASSOCIATED WITH THE CLOSED LOW. WILL WORD THE EARLY PART OF THE
FORECAST BASED ON THE LATEST RADAR TRENDS FOR AREAL COVERAGE, BUT
EXPECT COVERAGE TO BECOME SCATTERED WITH THE LOSS OF DAYTIME HEATING.

THE LIMITING FACTOR FOR THUNDERSTORMS HAS BEEN THE LACK OF LOW LEVEL
MOISTURE. DESPITE 500 MB TEMPS NEAR -20C, 850 TO 500 MB LAPSE RATES
OF 6.5 C/KM AND VERTICAL TOTALS AROUND 25 C ARE MODEST INDICATIONS
OF INSTABILITY TO GO ALONG WITH FORECAST SOUNDINGS WITH CAPE OF 1000
J/KG OR LESS. SCATTERED SHOWERS WITH A CHANCE OF THUNDERSTORMS
CONTINUES TO LOOK GOOD FOR THE REMAINDER OF THE EVENING. AS THE
DIURNAL COMPONENT WEARS OUT, Q-VECTOR FORCING WILL BE WEAK AND
ISENTROPIC ASCENT WILL BECOME DISORGANIZED THROUGH THE WEST FLANK OF
THE UPPER LOW. WITH THIS IN MIND, FEEL THAT THE MODEL MOISTURE AND
QPF IS OVERDONE TO OUR WEST, BUT THE WEAKNESS OVER SE MICHIGAN LOOKS
GOOD. A CHANCE OF SHOWERS WILL CONTINUE TO COVER THE SITUATION WELL.

THERE WILL BE A CHANCE OF SHOWERS DURING THE DAYLIGHT HOURS OF THE
MORNING ON SATURDAY AS WRAP-AROUND MOISTURE LINGERS. DURING THE
AFTERNOON, COLD AIR WILL BE REINFORCED IN THE UPPER LEVELS AS A LOBE
OF ENERGY ROTATES THROUGH THE PATTERN. DCVA AND UPPER JET SUPPORT
WILL BE WEAK AS THE WAVE LOOKS SHEARED IN THE MODEL DATA BUT DIURNAL
HEATING WILL BE ENOUGH TO KEEP SCATTERED SHOWERS IN THE FORECAST
WITH A CHANCE OF THUNDERSTORMS INTO SATURDAY EVENING. INSTABILITY
WILL REMAIN MODEST WITH LIMITED LOW LEVEL MOISTURE.

ONCE AGAIN, AS THE DIURNAL COMPONENT WEARS OFF WE WILL HAVE TO RELY
ON SYNOPTIC FORCING FOR ANY CHANCE OF RAIN OVERNIGHT SATURDAY NIGHT,
WHICH WILL BE EVEN WEAKER AND LESS ORGANIZED THAN TONIGHT AS THE
UPPER SYSTEM BEGINS TO DRIFT EAST. THIS WILL BE FOLLOWED BY A REPEAT
PERFORMANCE ON SUNDAY AND SUNDAY NIGHT AS THE UPPER LEVEL THERMAL
TROF LINGERS OVER THE AREA.

PLAN TO KEEP A CHANCE OF RAIN IN THE FORECAST FOR MONDAY AS THE LAST
LOBE OF ENERGY ROTATES THROUGH THE UPPER LOW, THEN THE GENERAL TREND
HEADING INTO THE MID WEEK PERIOD IS TO SPEED UP THE EXIT OF THE
SYSTEM BY TUESDAY. ALL OF THE MODELS ARE PARTICIPATING IN THIS TREND
WITH HIGH PRESSURE OVER OUR AREA BY TUESDAY NIGHT AND SOUTHERLY
RETURN FLOW DEVELOPING OVER THE GREAT LAKES THROUGH WEDNESDAY.
CONSIDERING THE ZONAL LONG WAVE PATTERN, MODEL DIFFERENCES ARE SMALL
BY THURSDAY ON A SHORT WAVE MOVING ALONG THE CANADIAN BORDER. ALL
SHOW THE WAVE OVER THE NORTHERN PLAINS AND NORTHWEST ONTARIO HEADING
INTO THURSDAY MORNING. THE AVN THEN TAKES THE SYSTEM INTO EASTERN
CANADA BY FRIDAY WITH A WEAK FRONT TRAILING THROUGH THE NORTHERN
GREAT LAKES. FOR NOW, PLAN TO MAINTAIN DRY CONDITIONS WITH WARMING
TEMPERATURES FROM WEDNESDAY THROUGH FRIDAY FOR SE MICHIGAN.

.DTX...NONE.

BT