Severe Thunderstorm Warning 37, NWS Gaylord, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1140 AM EDT SUN JUL 22 2001

WEAK DISORGANIZED SURFACE PRESSURE PATTERN WILL PERSIST ACROSS THE
GREAT LAKES REGION THIS AFTERNOON...WITH WEAK RIDGING PERSISTING
(FOR THE MOST PART) ALOFT. MAIN CONCERN FOR THE AFTERNOON...AS IN
THE PAST FEW DAYS...REVOLVES AROUND ADDITIONAL SHOWER AND
THUNDERSTORM DEVELOPMENT.

THERE IS A VERY SIMILAR PATTERN ACROSS THE REGION THIS AFTERNOON
COMPARED TO RECENT DAYS. DYNAMIC FORCING IS WEAK ONCE AGAIN...MAINLY
LIMITED TO A FEW WEAK SHORT WAVES (CONVECTIVELY INDUCED FOR THE MOST
PART) RIDING OVER THE UPPER RIDGE CENTERED JUST TO OUR WEST. SOME OF
THIS SHORTWAVE ENERGY WILL MOVE ACROSS THE FORECAST AREA THIS
AFTERNOON. NUMEROUS CONVECTIVE AND LAKE BREEZE BOUNDARIES WILL BE
THE ONLY OTHER FOCUS FOR AFTERNOON CONVECTION. IN FACT...WE WILL BE
GETTING UNDER THE UNFAVORABLE RIGHT EXIT REGION OF A 60 KNOT UPPER
JET BY LATE AFTERNOON.

INSTABILITY THIS AFTERNOON WILL BE QUITE GOOD ONCE AGAIN. MODIFIED
12Z APX SOUNDING (WHICH WILL NOT CHANGE MUCH BY EVENING) FOR 87/68
(T/TD) YIELDS A CAPE VALUE AROUND 2500 J/KG AND LI OF -8. SCATTERED
SHOWERS AND THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AS INSTABILITY
INCREASES AND BOUNDARIES INTERACT. LIMITING FACTORS FOR SEVERE
WEATHER REMAIN THE LACK OF A WEAK CAP...WEAK WIND FIELDS AND HIGH
FREEZING AND WBZ LEVELS (13000 FEET AND 11000 FEET RESPECTIVELY).
MAIN SEVERE THREAT WILL BE MARGINAL SEVERE GUSTS AS PULSING CELLS
COLLAPSE. THIS THREAT WILL BE INCREASING LATE THIS AFTERNOON/EARLY
THIS EVENING AS DRIER MID LEVEL AIR WORKS IN FROM MINNESOTA.

ANY THUNDERSTORMS THAT DEVELOP HAVE THE POTENTIAL TO BE HEAVY RAIN
PRODUCERS GIVEN THE JUICY AIRMASS IN PLACE (PWAT VALUES AROUND 1.5
INCHES AND K INDICES AROUND 35) AND WEAK WIND FIELDS (SLOW CELL
PROPAGATION).

.APX...NONE.

BAK