Flood in Michigan, February 22, 2002

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
322 AM EST FRI FEB 22 2002

HIGH PRESSURE EXTENDING FROM THE CENTRAL PLAINS TO NORTHERN ONTARIO
IS ADVECTING DRY LOW LEVEL AIR ACROSS THE GREAT LAKES PER CURRENT
SATELLITE LOOPS AND SFC DEWPTS. SATELLITE FOG PRODUCT NOW HAS BACK
EDGE OF CLOUDS EXTENDING FROM JUST SOUTH OF OSC TO BIV.
EXTRAPOLATION FROM SATELLITE IMAGERY BRINGS CLEARING INTO THE TRI
CITIES AROUND 09 Z AND FLINT BETWEEN 10 AND 11Z. EDGE OF THE CLOUD
COVER LINES UP WELL WITH DRY AIR INTRUSION AT 850MB. 00Z MESO ETA IS
RUNNING A LITTLE FAST ON BRINING CLEARING ACROSS THE FORECAST AREA.
BASED ON SATELLITE TRENDS...EXPECT THE DETROIT METRO AREA TO SEE
CLEARING BETWEEN 12 AND 14 Z THIS MORNING. ONCE SKIES CLEAR...NEXT
FORECAST CONCERN WILL BE WITH PRECIP CHANCES THE LATER HALF OF THIS
WEEKEND.

THE 00Z MODEL SUITE IS IN GOOD GENERAL AGREEMENT IN SURFACE AND
UPPER LEVEL FEATURES ACROSS THE GREAT LAKES REGION THROUGH 42
HOURS...BY 48 HOURS HOWEVER DIFFERENCES ARISE IN TIMING OF THE
ARCTIC FRONTAL BOUNDARY INTO THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES AND WITH THE TIMING AND STRENGTH OF THE SYSTEM
MOVING ACROSS SOUTHERN CANADA. THE ETA MODEL IS MUCH FASTER THAN THE
AVN...CANADIAN AND UKMET IN BRINGING THE SURFACE FRONTAL BOUNDARY
INTO THE WESTERN GREAT LAKES ON SUNDAY AS IT IS MUCH STRONGER WITH
THE SURFACE LOW TO THE NW OF LAKE SUPERIOR. THE ETA HAS TRENDED A
LITTLE WEAKER WITH THIS SYSTEM...AND WITH THE OTHER MODELS
SUGGESTING A WEAKER SYSTEM TO THE NORTH...I PREFER THE SLOWER TIMING
OF THE AVN.

FOR TODAY...SHORT WAVE RIDGE AXIS CURRENTLY EXTENDING ACROSS UPPER
MICHIGAN WILL MOVE INTO SE MICHIGAN THIS AFTERNOON ALONG WITH SFC
HIGH PRESSURE. AS MENTIONED EARLIER...LOW LEVEL DRY AIR ADVECTION
WILL QUICKLY SCOUR OUT CLOUDS THIS MORNING. I EXPECT THAT THE CLOUDS
WILL LINGER INTO THE EARLY AFTERNOON ACROSS THE THUMB UNDER A
NORTHERN FLOW. WITH 925MB TEMPS AROUND -10C...DELTA TS WILL BE
AROUND 12C. THOUGH NOT ENOUGH FOR SNOW SHOWERS...CERTAINLY ENOUGH
INSTABILITY TO GENERATE SOME LAKE STRATO CU. CURRENT SATELLITE LOOP
IN FACT SHOW WIDESPREAD LAKE STRATO CU ACROSS CENTRAL AND SOUTHERN
LAKE MICHIGAN. I DO NOT EXPECT THE LAKE CLOUDS TO PERSIST VERY LONG
IN THE AFTERNOON HOWEVER AS VERY DRY AIR CONTINUES TO ADVECT OVER
LAKE HURON FROM ONTARIO AND AS THE SFC FLOW QUICKLY BECOMES ANTI
CYCLONIC. BASED ON UPSTREAM TEMPS FROM YESTERDAY...I WILL SIDE WITH
THE SLIGHTLY COOLER MAV/ETA 2M TEMPS FOR HIGHS TODAY.

TONIGHT...SURFACE RIDGE AXIS SLIDES ACROSS SE MICHIGAN. NEARLY CALM
WINDS AND A DRY AIRMASS WILL SET THE STAGE FOR GOOD RADIATIONAL
COOLING. MODEL SOUNDINGS SHOW HIGH LEVEL MOISTURE ON THE INCREASE.
SINCE HIGH MID/HIGH LEVEL RH IS NOT PROGGED TO PUSH IN UNTIL 9 TO
12Z...THERE WILL BE SEVERAL HOURS OF GOOD RADIATIONAL COOLING.
LOOKING AT UPSTREAM TEMPS IN THE TEENS (AND A FEW SINGLE DIGITS)...I
WILL DROP TEMPS A COUPLE OF DEGREES BELOW GUIDANCE.

SATURDAY AND SATURDAY NIGHT...STRONG LOW LEVEL WARM AIR ADVECTION
PATTERN DEVELOPS AHEAD OF THE FRONTAL BOUNDARY THAT PUSHES INTO THE
PLAINS. SOME MODEST OMEGA FIELDS AND 295K ISENTROPIC ASCENT WILL
INCREASE MID LEVEL MOISTURE (6-12K FT) TO 95 PCT...WITH CONDENSATION
PRESSURE BEFITS PROGGED TO FALL TO 10MB BY 00Z SUN. BOTH THE ETA AND
AVN BRING THE BEST LIFT ACROSS THE FORECAST AREA BETWEEN 00 AND 06Z.
STEEPENING MID LEVEL LAPSE RATES (6-7 C/KM FROM 700-500MB) WOULD
SUPPORT SOME SHOWERY PRECIP. BIG LIMITING FACTOR HOWEVER IS THE VERY
DRY AIRMASS (LESS THAN 30 PCT RH) BETWEEN THE SFC AND 800MB. THUS
THINK THAT A DRY FORECAST IS STILL THE WAY TO GO. HOWEVER...I WILL
ADD A 30 PCT CHNC POP IN THE TRI CITIES AND THUMB...GIVEN BETTER
LIFT AND A LITTLE HIGHER LOW LEVEL RH. CRITICAL THICKNESS POINT TO
MAINLY RAIN...HOWEVER WITH WET BULB ZERO HEIGHTS AROUND 600FT...I
WILL CARRY A CHNC OF RAIN AND SNOW. GIVEN THE STRENGTH OF THE RETURN
FLOW...I PREFER THE WARMER MAV TEMPS OVER THE FWCS.

IN SIDING CLOSER TO THE AVN SOLUTION...I WILL TREND TEMPS A LITTLE
WARMER ON SUNDAY AND PUSH BACK PRECIP CHANCES TO LATE. EVEN THE
SLOWER SOLUTIONS STILL BRING THE ARCTIC FRONT THROUGH ON
MONDAY...THUS NO CHANGES NEEDED TO THE EXTENDED.

.DTX...NONE.

CONSIDINE