Special Marine Warning 49, NWS Gaylord, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
415 AM EDT SUN JUL 21 2002

THE MAIN FORECAST QUESTIONS THIS PACKAGE WILL BE CENTERED ON THE
CHANCE OF CONVECTION INTO MONDAY...AND THE AFTERNOON HIGHS THROUGH
THE PERIOD.

TODAY...THE CURRENT SURFACE CHART SHOWS A STORM SYSTEM CENTERED OVER
NORTHERN MINNESOTA...WITH A COLD FRONT LOCATED OVER THE CENTRAL
PLAINS AND A WARM FROM BETWEEN LAKE SUPERIOR AND JAMES BAY. THE
LATEST APX 88D AND IR SATELLITE SHOWS AN AREA OF MID LEVEL MOISTURE
MOVING OVER EAST UPPER MICHIGAN AND LAKE MICHIGAN...WHILE THE MQT
88D SHOWS AN AREA OF SHOWERS AND THUNDERSTORMS OVER WESTERN UPPER
MICHIGAN. THIS MOISTURE IS IN ADVANCE OF A 500MB TROUGH AND VORT MAX
MOVING OVER UPPER MICHIGAN. THE TROUGH AND VORT WILL SLOWLY MOVE
EAST OVER THE STRAITS/NORTHERN LOWER MICHIGAN THIS MORNING AND EXIT
INTO THE EASTERN LAKES THIS AFTERNOON. THIS WILL HELP SUPPORT SOME
LIFT OVER THE NORTHERN LAKES THROUGH THE MORNING HOURS. THE MAIN
HINDRANCE TO WIDESPREAD CONVECTION TODAY WILL BE THE EXTREMELY WARM
TEMPERATURES ALOFT SUPPORTING A CAP OVER MUCH OF THE FORECAST AREA.
700MB TEMPERATURES WILL WARM TO AROUND 11C THIS AFTERNOON WITH A
1000/500MB THCKN AROUND 5790M EXTENDING INTO NORTHERN LOWER MICHIGAN.
HOWEVER OVER EAST UPPER A THTE RIDGE WITH 850MB DEW POINTS AROUND
16C AND SURFACE DEW POINTS IN THE UPPER 60S TO LOWER 70S...WILL
GENERATE A LIFTED INDEX AROUND -3C WITH CAPES AROUND 1700 J/KG.
THEREFORE WILL MENTION A CHANCE OF SHOWERS AND THUNDERSTORMS OVER
EAST UPPER AND EXTREME NORTHERN LOWER MICHIGAN AWAY FROM THE CAP.
RAINFALL COULD BE HEAVY OVER EAST UPPER AND EXTREME NORTHERN LOWER
MICHIGAN THIS MORNING...AS PRECIPITABLE WATER VALUES NEAR 2 INCHES.
AFTERNOON HIGHS WILL BE IN TH LOWER 90S OVER THE SOUTHERN PORTIONS
OF THE FORECAST AREA AND THE MID AND UPPER 80S NORTH AS 850 MB
TEMPERATURES WARM TO BETWEEN 18C AND 20C.

TONIGHT...THE CENTRAL PLAINS STORM SYSTEM WILL MOVE TOWARD THE LAKES
REGION THROUGH THE EVENING...BECOMING LOCATED OVER EASTERN
WISCONSIN BY MIDNIGHT AND MOVING OVER LAKE MICHIGAN OVERNIGHT.
ADDITIONAL LIFT WILL BE SUPPLIED BY UPPER JET DYNAMICS. THE RIGHT
ENTRANCE REGION OF A 120KT 250MB JET WILL BEGIN TO INFLUENCE THE
FORECAST AREA BETWEEN 06Z AND 12Z MONDAY. THE ATMOSPHERE WILL REMAIN
UNSTABLE AS ABUNDANT LOW LEVEL MOISTURE REMAINS IN PLACE OF THE
STATE. 850MB DEW POINTS WILL REMAIN AROUND 16C WITH SURFACE DEW
POINTS BETWEEN 65 AND 70. THIS WILL GENERATE A LIFTED INDEX BETWEEN
-2C AND -4C WITH CAPES AROUND 1800 J/KG. PRECIPITABLE WATER VALUES
WILL REMAIN HIGH ALSO THROUGH THE OVERNIGHT HOURS...GENERALLY AROUND
2 INCHES. THEREFORE WILL ALSO MENTION THE CHANCE OF LOCALLY HEAVY
RAIN POSSIBLE FOR EAST UPPER AND EXTREME NORTHERN LOWER MICHIGAN.

MONDAY...THE SURFACE COLD FRONT WILL BE LOCATED OVER LAKE MICHIGAN
IN THE MORNING...BEFORE MOVING INTO THE EASTERN LAKES REGION BY THE
EVENING. THE AIRMASS ALONG AND AHEAD OF THE COLD FRONT WILL REMAIN
UNSTABLE...AS SURFACE DEW POINTS REMAIN IN THE UPPER 60S AND 850MB
DEW POINTS REMAIN AROUND 16C. TO COMBINE WITH THE SURFACE
CONVERGENCE ALONG THE SURFACE FRONT...ADDITIONAL LIFTING WILL BE
SUPPLIED BY THE UPPER JET. THE RIGHT ENTRANCE REGION OF THE UPPER
JET WILL REMAIN OVER NORTHERN LOWER MICHIGAN INTO THE AFTERNOON. DUE
TO THE OVERALL SLOW MOVEMENT OF THE FRONT...WILL MENTION SHOWERS AND
THUNDERSTORMS IN THE FORECAST THROUGH THE AFTERNOON FOR NORTHERN
LOWER MICHIGAN...ENDING IN THE MORNING OVER EAST UPPER MICHIGAN.
HIGH TEMPERATURES WILL BE DIFFICULT FOR MONDAY. AS THE COLD FRONT
DROPS FROM EAST UPPER IN THE MORNING INTO NORTHERN LOWER...
COOLER AND DRIER AIR WILL FILTER IN. 850 MB TEMPERATURES DROP FROM
17C IN THE MORNING OVER EAST UPPER TO 14C...WHILE REMAINING AROUND
18C OVER NORTHERN LOWER MICHIGAN. THEREFORE WILL LEAN TOWARD THE
UPPER 70S OVER EAST UPPER AND MID TO UPPER 80S OVER NORTHERN LOWER
MICHIGAN.

MONDAY NIGHT...A FEW SHOWERS ARE POSSIBLE OVER THE SOUTHEAST
PORTIONS OF THE FORECAST AREA IN THE EVENING...AS THE COLD FRONT
SLOWLY DROPS SOUTH OF SAGINAW BAY. THE AIRMASS BEHIND THE FRONT WILL
BE MUCH DRIER AS SURFACE DEW POINTS DRY INTO THE MID 50S OVER
EAST UPPER AND IN THE UPPER 50S OVER OF SOUTHERN LOWER MICHIGAN.
850/500MB MOISTURE WILL DRY TO UNDER 50 PERCENT BY 12Z TUESDAY.
THEREFORE WILL MENTION SKIES BECOMING PARTLY CLOUDY OVERNIGHT WITH
SOME FOG.

.APX...NONE.

SWR