Hail and Damaging Winds in Michigan, July 30, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
350 PM EDT TUE JUL 30 2002

MAIN FORECAST CONCERNS ARE POPS THRU THU MORNING...AND SEVERE
POTENTIAL WED AFTN/NIGHT.

LATEST SURFACE ANALYSIS SHOWS A WEAKENING COLD FRONT EXTENDING FROM
MN THROUGH SD...WITH BROAD HOT/HUMID SWLY FLOW AHEAD OF IT. A WEAK
SFC TROUGH IS MOVING THRU THE AREA ATTM...AS WINDS OVER THE WESTERN
UP ARE WEST AND THE EASTERN UP WINDS REMAIN SW. WITH COLD FRONT TO
THE WEST...NOT MUCH SFC DRYING TONIGHT SO TEMPS SHOULD STAY UP WELL
ABV GUIDANCE TONIGHT. OTHERWISE...A VORT MAX OVER WY TONIGHT WILL
MOVE EAST TONIGHT...HELPING TO DEVELOP AND MCS ALREADY FORMING OVER
SD/SRN MN.

SEEMS LIKE ATMOSPHERE IS JUST TOO DRY AND CAPPED TO POP ANY
THUNDERSTORMS OFF OVER THE AREA TODAY/THIS EVENING (PER GOES
SOUNDINGS) DESPITE IMT WARMING TO 90/68 AND A SFC TROF MOVING THRU
THE AREA AND CAPE 2000-2500 J/KG ACROSS THE AREA. INITIALLY
CONTINUED WITH SCT POPS THIS EVENING. BUT GIVEN LACK OF ANY
SIGNIFICANT ACTIVITY ON RADAR...HAVE OPTED TO PULL POPS THIS EVENING.

LATE TONIGHT/WED MORN...FRONT MOVES S OF THE AREA THIS EVENING BUT
SHOULD MOVE N AGAIN AS THE MORNING GOES ON. THE ABV MENTIONED VORT
MAX AND ASSOCIATED MCS SHOULD MOVE INTO THE AREA BEFORE SUNRISE AND
EXIT THE EAST BY AFTN. WITH THE STRONG WLY FLOW ALOFT...H7-H5 LAPSE
RATES WILL INCREASE TO 7.5C/KM BY MORNING WITH ELEVATED CAPE VALUES
AROUND 1300 J/KG. DECENT UNIDIRECTIONAL SHEAR IS NOTED IN THE LOWEST
2 KM...AS 850 MB LLJ NOSES INTO THE AREA. BEING THAT THE CONVECTION
WOULD BE ELEVATED IN NATURE...SVR HAIL WOULD BE THE MAIN THREAT. WET
BULB ZERO HEIGHTS AROUND 10.5 KFT WOULD SUPPORT THIS. WILL THEREFORE
CONTINUE WITH SMALL 30 POPS FOR LATE TONIGHT. NO SVR WORDING TONIGHT
AS SPC PULLED THE UP OUT OF THE THEIR SLIGHT RISK AREA.

FORECAST STARTS TO GET A LITTLE MORE INTERESTING LATE WED AFTN AND
WED NIGHT AS THE DYNAMIC COLD FRONT/TROUGH APPROACHES THE AREA. 12Z
RUN ABOUT 6-12 HOURS SLOWER WITH THE EASTWARD PROGRESS OF THE
FRONT...HOWEVER AM NOT TOTALLY GOING TO BUY OFF ON THAT QUITE YET
GIVEN THE FAST AND ZONAL FLOW ALOFT AND SINCE THE ASSOCIATED VORT
MAX IS STILL OVER THE DATA VOID REGION OFF THE BRITISH COLUMBIA
COAST. THIS MAKES THE FORECAST A LITTLE MORE TRICKY...AND THUS
CONFIDENCE IS NOT AS HIGH WITH FORECAST DETAILS. EVEN IF THE SLOWER
SOLN IS CORRECT...THERE REMAINS PLENTY OF INSTABILITY THROUGH THE
EVENING AND EVEN THE OVERNIGHT AS CAPE REMAIN ABV 3000 J/KG THROUGH
05Z AT IWD...WITH HIGH 0-6KM SHEAR AND 0-3KM HELICITY VALUES. THERE
ALSO IS A 35-40 KT SW 850 LLJ ON THE SOUTH SIDE OF A 70 KT WESTERLY
500 MB SPEED MAX THAT WILL ENHANCE SHEAR LATE IN THE AFTN/EVENING.
SEEMS LIKE BEST INSTABILITY AND HODOGRAPH CURVATURE WILL BE OVER THE
NRN MN TMRW AFTN...SO MOST LIKELY SCENARIO WILL BE SUPERCELL
ACTIVITY WITH POSSIBLE TORNADOES AHEAD OF THE FRONT IN MN DURING THE
AFTN. THEN IT SHOULD FORM INTO BOW SEGMENTS WITH ISOLATED SUPERCELLS
AS IT MOVES TOWARD THE UP IN THE EVENING. LFC HEIGHTS ARE ABV 2000 M
SO CHANCE FOR TORNADOES IS LOW HERE. MAIN PROBLEM OVER THE UP WILL
BE WIND GUSTS TO 70 MPH WITH HAIL ABOVE 1 INCH. ONE NOTE...WILL BE
INTERESTING TO SEE WHAT HAPPENS DURING THE AFTN TMRW IF THERE ARE
LEFTOVER BOUNDARIES FROM MCS. CAP IS PRETTY STRONG DURING THE AFTN
DUE TO SIGNIFICANT 800 MB WAA...SO IT IS UNCERTAIN WHETHER
CONVECTION WILL BE ABLE TO BREAK THRU THE CAP EVEN IF THERE ARE
BOUNDARIES. WILL GENERALLY LEAVE THE FORECAST THE SAME FOR WED
AFTN...WITH THE FAR WEST HAVING THE TSTM CHANCES LATE DUE TO THETA-E
RIDGE NOSING INTO AREA LATE. WILL CONTINUE LIKELY WORDING ON WED
NIGHT. AREA STILL UNDER MODERATE RISK OF SVR BY SPC DAY 2.

FRONT SHOULD CLEAR THE AREA DURING THE MORNING THU. NO MAJOR
CONCERNS BEHIND THE FRONT OTHER THAN A LITTLE AFTN CU. DECENT MIXING
DURING THE AFTN SHOULD YIELD BRZY CONDITIONS WITH WINDS 20-30KT IN
MIXED LAYER. TEMPS AND DWPTS MUCH MORE REASONABLE...GENERALLY NEAR
NGM MOS GUIDANCE.

NO MAJOR CHANGES ON FRIDAY AS HIGH PRES REMAINS OVER THE AREA. DRY
WITH NEAR NORMAL TEMPS.

EXTENDED/SAT-TUE/...NO MAJOR CHANGES PLANNED TO THE ZONES. MRF/UKMET
ABOUT 24 HOURS FASTER THAN THE ECMWF IN MOVING A TROUGH OVER THE
AREA. THE UK/MRF BRING THE TROUGH THROUGH SUNDAY...AND THE ECMWF
WAITS UNTIL MONDAY MORNING. OTHER THAN THAT...MODELS ARE FAIRLY
CONSISTENT IN KEEPING A GENERAL ZONAL FLOW NR THE CANADIAN BORDER
THRU SUNDAY. WILL PROBABLY BE TOUGH TO TIME THE INDIVIDUAL SHORT
WAVES SO WILL LEAVE CHC POPS IN FOR SAT AND SUNDAY. OPERATIONAL MRF
IS FASTER AND MORE AMPLIFIED THAN THE ENSEMBLE MEMBERS ON MONDAY AND
TUESDAY. HOWEVER...ALL SHOW TROUGHINESS AND NWLY FLOW OVER THE AREA
MONDAY AND TUE SO WILL CONTINUE WITH DRY AND NEAR NORMAL TEMPS.

.MQT...NONE.

MRD