Winter Storm in Michigan, March 2, 2002

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
410 AM EST SAT MAR 2 2002

SNOW FIELD HAS EXPANDED ACROSS THE NORTHERN HALF OF THE FORECAST
AREA EARLY THIS MORNING. BOTH THE KDTX AND KGRR 88DS SHOWING SOME
BANDED STRUCTURE EMBEDDED WITHIN THE LARGER REFLECTIVITY SIGNATURE,
POSSIBLY FROM SOME ELEVATED CONVECTION.  THE PRIMARY LIFT APPEARS TO
BE ASSOCIATED WITH THE MID-TROP FRONT ALONG THE SHARP 500MB HEIGHT
GRADIENT.  GREATEST LIFT ACCORDING TO THE 00Z CYCLE RUNS SHOULD BE
CONCENTRATED AROUND 600-400MB, WITH THE ETA INDICATING ASCENT RATES
APPROACHING -30UB/S.  PRECIP SHIELD EXTENDS WELL TO THE SOUTHWEST OF
THE AREA ACROSS NORTHERN ILLINOIS AND EASTERN IOWA.  MEANWHILE, THE
DEVELOPING SURFACE LOW IS STILL ALONG THE TEXAS GULF COAST, WITH AN
INVERTED TROUGH EXTENDING INTO THE WESTERN LAKES REGION.

NCEP SUITE STILL OFFERING DIFFERING OPINIONS WITH REGARD TO THE
DEVELOPMENT AND TIMING OF THE STORM SYSTEM.  THE ETA CONTINUES TO BE
THE FASTEST AND WARMEST SOLUTION.  THE WARMTH APPEARS TO RESULT FROM
A COMBINATION OF A SLIGHTLY MORE WESTERLY TRACK, STRONG WARM
ADVECTION- THANKS IN PART TO 60KT FLOW AT 850MB- AND LATENT HEAT
RELEASE COINCIDENT WITH STRONG UVV/S.  THINK THAT THE DIABATIC HEAT
SIGNATURE IS TOO STRONG AT THE BASE OF THE GREATEST LIFT, WOULD
ANTICIPATE MORE COOLING OF THE COLUMN DUE TO THE STRONG ASCENT, NOT
WARMING BELOW.  FURTHERMORE, THE AVN HAS BEEN MORE CONSISTENT WITH
THE NEAR SURFACE FEATURE THE LAST COUPLE OF CYCLES, WHILE THE ETA
HAS TRENDED FARTHER EAST AND SLOWER EACH GO AROUND.  A PEAK AT THE
06Z ETA LOOKS MUCH MORE LIKE THE AVN SOLUTION. THEREFORE, STILL
FAVOR A PROGRESSION MORE SIMILAR TO THE SLOWER 00Z AVN/ETA-XX
SOLUTIONS.

COMPLICATING FACTORS ARE TIED TO RESILIANCY OF THE DRY AIR, EVIDENT
IN THE 00Z DTX RAOB, ACROSS THE SOUTHERN SECTIONS OF THE FORECAST
AREA AND TO THE DEGREE OF WARMING JUST ABOVE THE SURFACE THIS
AFTERNOON AND TONIGHT.  EXPECT THAT SNOWFALL WILL BE TEMPERED
GREATLY ACROSS THE METRO AREAS THIS MORNING, DUE TO THE SUB-CLOUD
DRYING AND CONCENTRATION OF LIFT WELL TO THE NORTH.  SURFACE
DEVELOPMENT SHOULD TAKE PLACE ACROSS TENNESSEE AND KENTUCKY THIS
AFTERNOON IN RESPONSE TO A COUPLED 300MB JET STRUCTURE.  THIS
COUPLING WILL INCREASE THROUGH THE AFTERNOON AND EVENING HOURS OVER
SOUTHERN LOWER, ALLOWING FOR ANOTHER ROUND OF SIGNIFICANT
PRECIPITATION TO AFFECT THE FORECAST AREA.  MID-LEVEL LAPSE RATES
INCREASE TO GREATER THAN 7C/KM, SETTING THE POTENTIAL FOR ELEVATED
CONVECTIVE ACTIVITY, WHICH IS ALREADY EVIDENT ACROSS MISSOURI AND
ILLINOIS. QPF VALUES ACROSS THE NORTHWEST HAVE BEEN CONSISTENT
AROUND AN INCH+ WITH 700MB MIXING RATIOS HOVERING AROUND 3-3.5G/KG
FOR ALMOST 24H.

PRECIP TYPE WILL BE AN ISSUE AS THE SURFACE LOW APPROACHES FROM THE
SOUTHWEST.  MODEL SOUNDINGS AND 1000-850MB AND 850-700MB THICKNESSES
INDICATE THAT THE PRECIP WILL REMAIN ALL SNOW FOR THE SAGINAW VALLEY
(EVEN THE WARMER ETA SUPPORTS SNOW WITH A POSSIBLE BRIEF MIXTURE).
BASED MODEL SOUNDINGS (INCLUDING THE 06Z ETA), THE RAIN/SNOW LINE
SHOULD BE ALONG A LINE FROM PORT HOPE TO OWOSSO TO BATTLE CREEK
LINE.  THEREFORE EXPECT SNOWFALL TOTALS TO BE IN THE 6-12 INCH RANGE
ACROSS THE SAGINAW REGION WITH A RAPID DROP OFF TO THE SOUTH AND
EAST, DUE TO THE CHANGE OVER, INITIAL DRY AIR AND THE NARROW
STRUCTURE TO THE FRONTOGENESIS LIFT. WILL ELEVATE THE SNOW ADVISORY
TO A WINTER STORM WARNING FOR THE NORTHWEST 3 COUNTIES AND SET A
WINTER WEATHER ADVISORY IN PLACE FOR THE SURROUNDING COUNTIES FOR
THE SNOWFALL TODAY (3-5 INCH RANGE) AND THE MIXED PRECIP THIS
EVENING. THE TIMING OF THE LIQUID PRECIP IS SOMEWHAT OF A CONCERN
(AFTER DARK OVER NEW SNOW), SO WILL MENTION THE POSSIBILITY OF
FREEZING RAIN IN THE ADVISORY AREA AS WELL.  TO THE SOUTH EXPECT
MUCH LESSER SNOW AMOUNTS DUE TO THE DRY AIR AND THE WARMER BOUNDARY
LAYER LATER IN THE DAY.  AS THE LOW PASSES BY THE PRECIP SHOULD
CHANGE BACK TO SNOW RAPIDLY, BEFORE ENDING ABRUPTLY AS THE MID-LEVEL
DRY SLOT ADVECTS OVERHEAD.

TEMPS WILL FALL THROUGH THE DAY ON SUNDAY AS STRONG COLD ADVECTION
USHERS IN THE ARCTIC AIRMASS.  LAKE EFFECT CLOUDS AND RESIDUAL SNOW
SHOWERS SHOULD STREAM INLAND OFF OF LAKE MICHIGAN INS THE
WEST-NORTHWEST GRADIENT FLOW.  IF THE GRADIENT RELAXES ENOUGH, WILL
HAVE TO WATCH FOR I-94 BAND DEVELOPMENT SUNDAY NIGHT AS COLD AIR
WRAPS AROUND THE SOUTHERN END OF LAKE MICHIGAN.  THE NEXT CLIPPER
SYSTEM APPEARS THAT IT WILL AFFECT THE REGION MONDAY NIGHT INTO
EARLY TUESDAY.  WILL ADD A CHANCE FOR SNOW FOR TUESDAY IN THE
EXTENDED PERIODS.  OTHERWISE NO OTHER CHANGES.

.DTX...WINTER STORM WARNING...TODAY AND TONIGHT...MIZ047>048-053.
       WINTER WEATHER ADVISORY...TODAY AND TONIGHT...
                                            MIZ049-054>055-60>62.

MANN