Severe Thunderstorm Warning 28, NWS Marquette, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
430 PM EDT SAT JUL 21 2001

12Z RAOBS/WATER VAPOR LOOP SHOW PERSISTENT PATTERN WITH RIDGE OVER
THE PLAINS AND TROUGHS OVER THE WEST AND EAST COASTS. A FEW WEAK
VORTS ARE UPSTREAM ASSOCIATED WITH CONVECTION OVER WESTERN
ONTARIO...SOUTHERN MANITOBA....SOUTHERN MINNESOTA...WESTERN NORTH
DAKOTA. VIS SATELLITE/KMQT RADAR SHOW THUNDERSTORMS DEVELOPING ALONG
CONVERGING LAKE BREEZES OVER THE EASTERN CWA.

ANOTHER WARM AND MUGGY NIGHT TONIGHT WITH DEWPOINTS IN THE UPPER
60S/LOWER 70S. PRECIP WILL BE A SOMEWHAT TRICKY FORECAST...AT LEAST
FOR TONIGHT. EXPECT ISOLATED THUNDERSTORMS THIS EVENING WITH STRONG
DIURNAL HEATING AND INSTABILITY. 12Z ETA/AVN BOTH DEVELOP A COMPLEX
OVER MINNESOTA THIS EVENING AND TRACK IT EASTWARD ACROSS THE CWA.
COMPARED TO CURRENT CONVECTION OVER SOUTHERN MINNESOTA/IOWA AND
CORFIDI VECTOR/THICKNESS PATTERN WOULD EXPECT THIS PRECIP TO STAY
SOUTH OF THE CWA...ALTHOUGH POSSIBLY AFFECTING THE SOUTHERN CWA
DURING THE EARLY MORNING HOURS. EXPECT MORE DIURNAL LAKE-BREEZE
CONVECTION ON SUNDAY BUT WILL WORD IT AS MAINLY IN THE AFTERNOON
NORTH AND WITH NO TIMING IN THE SOUTH TO COVER ANY POSSIBLE REMNANTS
THAT LINGER THIS FAR NORTH. ANOTHER HOT DAY ON SUNDAY WITH
TEMPERATURES CLIMBING TO NEAR 90 IN THE INTERIOR...WITH 90 BEING THE
RECORD AT MQT. SOUTHERLY GRADIENT LOOKS WEAKER THAN PREVIOUS
RUN...SO LAKE BREEZE COULD MAKE SOME PROGRESS INLAND.

SUNDAY NIGHT...EXPECT DIURNAL CONVECTION TO CONTINUE INTO THE
EVENING. WITH SLOWER FRONTAL MOVEMENT DO NOT EXPECT SYNOPTIC FORCING
TO REACH THE CWA UNTIL MORNING. ANOTHER COMPLEX DEVELOPS AHEAD OF
THE FRONT OVER NORTH DAKOTA AND THE ETA/AVN DIVERGE WITH THE
HANDLING OF IT. AVN SHOWING PRECIPITABLE WATERS FROM 0.5" TO 1.0"
HIGHER THAN THE ETA AND IS OVERDONE PER PMDHMD. AVN ALSO DEVELOPS A
LARGE COMPLEX WHICH BRINGS 2 INCHES OF PRECIP TO THE KEWEENAW SUNDAY
NIGHT. ETA WEAKER WITH THE FEATURE AND TRACKS IT MORE NNE INTO
ONTARIO ALONG CORFIDI VECTORS. SOME PRECIP MAY BRUSH THE CWA AFTER
MIDNIGHT BUT MAJORITY WILL BE LEFTOVER FROM SUNDAY. WILL TREND BACK
AND MENTION SCATTERED SHOWERS AND THUNDERSTORMS MAINLY IN THE
EVENING.

MONDAY THROUGH TUESDAY...QUESTION REMAINS AS TO THE SPEED AND
STRENGTH OF THE SURFACE FRONT. ETA AND AVN TRY TO BRING THE FRONT
THROUGH MONDAY BUT WITH LITTLE UPPER SUPPORT. 12Z CANADIAN IS
SLOWER...BRINGING THE FRONT ACROSS THE CWA MONDAY NIGHT. ETA
EXTENSION BRINGS THE UPPER SHORTWAVE THROUGH LATE MONDAY NIGHT AND
TUESDAY. BECAUSE OF THIS WILL CONTINUE CHANCE POPS FOR SHOWERS AND
THUNDERSTORMS MONDAY AS WELL AS A CHANCE FOR LINGERING SHOWERS
MONDAY NIGHT AND TUESDAY. TEMPERATURES WILL BEGIN TO COOL MONDAY AND
MONDAY NIGHT WITH SLIGHTLY BELOW NORMAL TEMPERATURES ON TUESDAY.

IN THE EXTENDED...AVN/MRF SLOW THE PROGRESS OF THE FRONT AFTER IT
PASSES THROUGH THE CWA...BRINGING IT MORE INTO LINE WITH THE OTHER
EXTENDED MODELS. BEHIND IT...ALL ARE SIMILAR BUILDING HIGH PRESSURE
OVER NORTHERN ONTARIO AHEAD OF AN APPROACHING SHORTWAVE RIDGE.
MRF/AVN/CANADIAN ARE MORE AMPLIFIED WHILE THE ECMWF/UKMET ARE LESS
SO. MRF ENSEMBLES SEEM EQUALLY SPLIT AS TO THE AMPLITUDE OF THE
SHORTWAVE RIDGE MIDWEEK BUT ARE SURPRISING SIMILAR WITH THE TIMING.
MRF SEEMS TO BE OVERDOING THE COLD AIR BY THURSDAY MORNING...SIMILAR
TO WHAT THE ECMWF WAS OVERDOING YESTERDAY. EXPECT 850MB TEMPS TO
DROP TO AROUND 10C GIVING HIGHS AS LOW AS 70F. AS THE PATTERN
PROGRESSES...NEXT SHORTWAVE TROUGH AND COLD FRONT APPROACH NEXT
WEEKEND. ALTHOUGH TIMING IS UNCERTAIN BY DAY 7...DO NOT EXPECT
PRECIP TO REACH THE CWA BY; SATURDAY. SUNDAY LOOKS LIKE THE BETTER
CHANCE AND WILL HOLD OFF ON PRECIP FOR NOW.

THANKS FOR COORD WITH APX.

.MQT...NONE.

JHB