Flood in Michigan, February 9 to 14, 2001

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
408 AM EST FRI FEB 9 2001

CURRENT BATCH OF SHOWERS- ASSOCIATED WITH THE SURFACE WARM FRONT, A
CONCENTRATED REGION OF 850-700MB THETA-E ADVECTION, AND AN DEEP
ELEVATED CONVECTIVE LAYER (AS PER ETA-22 850-500MB NEGATIVE EQUIV.
POTENTIAL VORTICITY)- IS NOW EXITING SOUTHEASTERN LOWER TO THE
EAST.  THE SURFACE WARM FRONT HAS ACCELERATED NORTHWARD ACROSS
REGION.  THE FRONT HAS LAGGED SOME ALONG THE LAKESHORE REGIONS,
WHERE THE ICE COVER HAS KEPT THE SURFACE LAYER A BIT COLDER.

NCEP SUITE CONVERGING ON A COMMON SOLUTION.  ALTHOUGH, THE CURRENT
PROGS CONTINUE TO BE TOO FAST WITH THE PROGRESSION OF SURFACE
FEATURES AND 24H/36H DPROG/DT ANALYSIS INDICATE A SLOWING TREND IN
THE ETA-22 AND AVN SOLUTIONS.  SEVERAL FACTORS POINT TOWARD A SLOWER
SOLUTION THAN INDICATED IN THE CURRENT CYCLE/S OFFERING. 1) GREATER
OBSERVED BAROCLINICITY THAN INDICATED BY ALL THE PROGS ACROSS THE
SOUTHERN PLAINS (A RESULT OF THE SHALLOW ARCTIC AIRMASS ACCELERATING
SOUTHWARD ALONG THE LEE OF THE ROCKIES) WILL RESULT IN A SLIGHTLY
STRONGER (AND SLOWER) SURFACE WAVE. 2) THE SURFACE LOW TRACK WILL
PARALLEL THE SOUTHWESTERLY 500MB FLOW UNTIL THE NORTHERN STREAM
SHORTWAVE APPROACH FROM THE WEST LATE TODAY.  BASED ON GOES-EAST WV
IMAGERY, THE VORT MAX PROGRESSION IS SLIGHTLY SLOWER THAN
PROJECTED.  THE NET RESULT WILL BE A DELAY IN THE WIDESPREAD SHOWER
ACTIVITY UNTIL AROUND MIDDAY. UNTIL THAT TIME, SCATTERED SHOWERS ARE
ANTICIPATED.  FURTHERMORE, COLD FRONTAL PASSAGE SHOULD BE DELAYED BY
A COUPLE OF HOURS, WHICH WILL HOLD OFF THE CHANGE TO SNOW UNTIL THE
EVENING HOURS.  DURING THE LATE MORNING TO MID AFTERNOON HOURS, A
SECONDARY REGION OF THETA-E ADVECTION AROUND 900MB, A NEUTRAL
PROFILE IN THE 850-500MB LAYER, AND THE PRESENCE OF A STRONG
LOW-LEVEL JET WILL SUPPORT THE POTENTIAL FOR A FEW THUNDERSTORMS,
ESPECIALLY ACROSS THE SOUTH.  RAINFALL POTENTIAL IS QUITE IMPRESSIVE
FOR FEBRUARY WITH PWS CLIMBING ABOVE AN INCH. HOWEVER, WITH THE
BREAK IN THE ACTION EARLY THIS MORNING, A SNOWPACK THAT SHOULD
RESIST RAPID MELTING DUE TO ITS HIGH ICE COMPOSITION, AND A
TRANSIENT SHOWER PATTERN, THE POTENTIAL FOR FLOODING APPEARS TO BE
MITIGATED SOME. SO WILL HOLD OFF ON ISSUING ANY HYDRO HEADLINES AT
THIS TIME.

THE ETA-22 CONTINUES TO ADVERTISE A 90KT LOW-LEVEL JET AT AROUND
800MB.  HOWEVER, THE DTX ETA-6 IS LESS ROBUST WITH ROUGHLY AN 80KT
MAX (STILL IMPRESSIVE THOUGH).  KDTX WSR-88D VWP INDICATES 50KTS
JUST OFF THE DECK.  THIS MORNING, EVEN WITH THE STRONGER SHOWER
ACTIVITY BEHIND THE SURFACE WARM FRONT, WE COULD ONLY MANAGE GUSTS
TO NEAR 30KTS.  THE STRONG WARM ADVECTION JUST ABOVE THE SURFACE
WILL PRECLUDE MIXING A GOOD PORTION OF THE HIGH MOMENTUM DOWN TO THE
SURFACE WITHOUT THE HELP OF CONVECTION, SO WILL KEEP WINDS SUSTAINED
IN THE 20-30MPH RANGE WITH HIGHER GUSTS, BUT NO ADVISORY.  ONCE THE
COLD FRONT PASSES AND THE VERY STRONG COLD ADVECTION AND DNVA AFFECT
THE REGION, AND THE ASSOCIATED SUBSIDENCE, THE WINDS ABOVE THE
BOUNDARY LAYER DIMINISH SUBSTANTIALLY (AROUND 45KTS).  ADDITIONALLY,
THE STRONG POST-FRONTAL SUBSIDENCE WILL LIMIT THE SNOW SHOWER
ACTIVITY AS THE COLUMN DRIES OUT RAPIDLY BEHIND THE SURFACE WAVE,
LEAVING ONLY RESIDUAL FLURRIES.  EXPECT THAT LAKE STRATOCU WILL
LINGER THROUGH EARLY SATURDAY UNDERNEATH THE SUBSIDENCE INVERSION,
BEFORE SOME MORE BOUNDARY LAYER DRYING TAKES PLACE.  SNOW PRODUCTION
SHOULD BE NEAR NILL WITH THE BASE OF THE INVERSION AROUND 4KFT AND
LOW DEWPOINTS.

THE WILD TEMPERATURE SWING WILL BE ANOTHER FACTOR TODAY, AS TEMPS
ARE ALREADY CLOSE TO 50 IN THE WARM SECTOR.  ACROSS THE FAR NORTH,
THE WARM FRONT IS MEETING SOME RESISTANCE, BUT ANTICIPATE A DECENT
TEMP RISE THERE AS WELL.  TONIGHT THE TEMPS WILL PLUMMET A QUICK 20
DEGREES IN THE FIRST COUPLE HOURS BEHIND THE FRONT BEFORE STABILIZING
INTO A STEADY FALL.  TEMPS SLIGHTLY BELOW FWC VALUES APPEAR THE MOST
REASONABLE WITH THE RAIN THIS AFTERNOON AND THE TENDENCY TO UNDERDO
THE COOLING DUE TO STRONG COLD ADVECTION BEHIND THE SYSTEM.

.DTX...GALE WARNING LAKE HURON...TODAY AND TONIGHT.
       GALE WARNING LAKE ST CLAIR...THIS AFTERNOON AND TONIGHT.

MANN