Severe Thunderstorm Warning 15, NWS Gaylord, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1122 AM EDT SAT JUN 9 2001

WELL DEFINED SHORT WAVE AXIS IN SATELLITE/RADAR PUSHING ACROSS EASTERN
UPPER/LAKE MICHIGAN WITH A BAND OF ELEVATED SHOWERS/THUNDERSTORMS.
STILL A GOOD DEAL OF SUNSHINE OVER NORTHEAST LOWER WHERE TEMPERATURES
HAVE WARMED TOWARD 70 DEGREES.  APX 12Z SOUNDING STILL DRY IN THE LOW
LEVELS AND NOT CONDUCIVE TO ELEVATED INSTABILTY EARLY ON...GRB SOUNDING
CONTAINS A BETTER MID LEVEL MOIST LAYER AND APPEARS SHOWERS BEING FED
BY LOW LEVEL THETA-E ADVECTION FROM THE "BACKSIDE".  RUC ANALYSIS
SHOWALTER INDICES AT 14Z CONTINUE TO SHOW INSTABILITY GRADIENT OVER
NORTHERN LOWER WITH UNSTABLE VALUES UPSTREAM.  MAIN QUESTIONS FOR THIS
AFTERNOON DEAL WITH CURRENT PRECIPITATION AND POTENTIAL FOR SOME
SURFACE BASED ENHANCEMENT OVER NORTHEAST LOWER.

EASTERN UPPER...INITIAL BAND OF SHOWERS SHOULD MOVE THROUGH EASTERN
UPPER BY 17Z BASED ON CURRENT EXTRAPOLATION.  VORTICITY CENTER OVER
CENTRAL LAKE SUPERIOR WILL DROP ACROSS EASTERN UPPER DURING THE
AFTERNOON...WITH ADDITIONAL CLOUD COVER OVER THE LAKE ALSO EXPECTED TO
ADVECT SOUTHEAST DURING THE AFTERNOON.  MAY SEE SOME INITIAL CLEARING
BEHIND INITIAL PRECIPITATION AREA...BUT ADDED LOW LEVEL MOISTURE DUE TO
RAINFALL SHOULD RESULT IN A QUICK BUILDUP OF CU.  THIS DIURNAL CLOUD
COVER PLUS CLOUD COVER ADVECTING IN OFF THE LAKE WILL PROBABLY RESULT
IN LESS SUNSHINE THAN INITIALLY THOUGHT.  KMQT 88D SHOWS SOME SPOTTY
SHOWERS AROUND VORTICITY CENTER...AND MODIFIED RUC SOUNDINGS FOR 70/55
PUSH CAPES NEAR 1000 J/KG...SO WILL CONTINUE TO MENTION SCATTERED
PRECIPITATION DURING THE AFTERNOON AND GO WITH A MORE PESSIMISTIC
MOSTLY CLOUDY.  IN ADDITION...WILL MAKE A DOWNWARD ADJUSTMENT TO
TEMPERATURES DUE TO MORE CLOUD COVER.

NORTHERN LOWER...MODIFIED 12Z APX SOUNDING FOR 75/48 YIELDS CAPES
AROUND 700 J/KG...THOUGH NOT QUITE THERE YET ADDITIONAL SHOWERS ARE
ALREADY POPPING UP ALONG LEADING EDGE OF THE MAIN LINE...SO FORCING
WITH SHORT WAVE ENOUGH TO OVERCOME SOME SURFACE BASED NEGATIVE AREA.
EXPECT THIS TREND TO CONTINUE AS SHORT WAVE MOVES INTO SOUTHEAST
COUNTIES WHERE AIR MASS WILL BE A LITTLE MORE UNSTABLE.  BEHIND THIS
INITIAL LINE LOOKS LIKE SKIES WILL CLEAR OVER NORTHWEST LOWER THOUGH
MORE CU SHOULD FORM...LIKE EASTERN UPPER MODIFIED RUC SOUNDINGS BY 21Z
FOR 70/55 YIELD CAPES ABOVE 1000 J/KG...AND THAT LIKELY TO BE A
CONSERVATIVE WARM UP.  WILL CONTINUE MENTION OF CHANCE POPS FOR THE
AFTERNOON ACROSS NORTHWEST LOWER BEHIND INITIAL WAVE OF SHOWERS FOR
POTENTIAL OF SOME ADDITIONAL SHOWERS POPPING UP...AND GO WITH A LITTLE
MORE CLOUD COVER FOR NORTHEAST LOWER ZAS MOST OF THE AFTERNOON NOW LOOKS
TO BE MOSTLY CLOUDY. WILL CHECK OVER 15Z OBS BEFORE MAKING ANY
TEMPERATURE ADJUSTMENTS.

UPDATED ARBZFPAPX WILL BE OUT BY 1550Z.

.APX...NONE.

JPB