Heavy Snow Warning 1, NWS St. Louis, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
1139 PM CST SUN MAR 19 2006

.DISCUSSION...
UPDATED AFD...WITH ADDITIONAL COUNTIES ADDED TO
WINTER STORM WATCH. HUGE SURFACE HIGH COVERED NORTHERN AND CENTRAL
CANADA AND MUCH OF THE EASTERN HALF OF THE COUNTRY TODAY. LOW
PRESSURE SYSTEMS WERE LOCATED OVER THE CENTRAL ROCKIES. VERY DRY
AIR IS ENTRENCED ACROSS THE AREA UNDER THE HIGH WITH SURFACE
DEWPOINTS IN THE TEENS ACROSS MOST OF THE REGION. THIS IS A LITTLE
LOWER THAN LAST SUNDAY AT THIS TIME. WITH THE DRY AIR IN
PLACE...WILL TAKE AWHILE TO SATURATE THE LOWER LEVELS. THE LOW
PRESSURE SYSTEM IS FORECAST TO MOVE/DEVELOP INTO THE SOUTHERN
PLAINS BY MONDAY EVENING AND THEN INTO KENTUCKY BY TUESDAY
MORNING.

THE GFS AND UKMET ARE FAIRLY SIMILAR BY MONDAY MORNING WITH A 160 KT
H3 JET OVER PA/NY EASTWARD WITH A 100 KT MOVING INTO WESTERN TX.
SIGNIFICANT DIVERGENCE FORECAST ACROSS THE REGION BY MONDAY EVENING
WHICH WILL ENHANCE THE LOW LEVEL CONVERGENCE.

THE MODELS CONTINUE TO BE SIMILAR IN FORECASTING AN UPPER LEVEL
CLOSED LOW WHICH WILL AFFECT OUR AREA MONDAY NIGHT AND EARLY
TUESDAY. THE UKMET AND GFS ARE SIMILAR WITH YESTERDAY/S RUN AND
CONTINUE TO FORECAST A CLOSED H5 LOW NEAR STL TUESDAY MORNING.
NEXT SHORT WAVE IS FORECAST TO AFFECT THE AREA ON THURSDAY.

THE NAM/S BUFKIT FORECAST IS CONSISTENT WITH SATURDAY/S FORECAST
WITHIN A COUPLE OF HOURS OF ONSET OF PRECIPITATION ACROSS THE
AREA. WITH THE DRY AIR IN PLACE...MODEL MAY BE FORECASTING THE
ONSET TOO SOON. EVAPORATIVE COOLING IS EXPECTED TO BE A BIG FACTOR
THOUGH WITH DRY AIR NEAR THE SURFACE. MOST OF THE REGION SHOULD
SEE THE ONSET AS SNOW. SEVERAL HOURS LATER A LAYER IS FORECAST TO
DEVELOP ABOVE FREEZING BETWEEN 5 AND 10 THOUSAND FEET. A MIXTURE
OF SLEET WITH RAIN IS POSSIBLE AT THAT TIME ESPECIALLY NEAR THE
I-70 CORRIDOR. THE HEAVIEST SNOW ACCUMULATION IS EXPECTED TO BE
NORTH OF US HIGHWAY 36 WHERE THE WINTER STORM WATCH REMAINS IN
EFFECT.

IN THE EXTENDED PERIOD...THE GFS AND EUROPEAN FORECAST A H5 SHORT
WAVE NEAR THE KS/MO BORDER THURSDAY MORNING. UPPER RIDGE IS
FORECAST TO BUILD ACROSS THE ROCKIES BY NEXT WEEKEND.

&&

.AVIATION...
FOR THE 06Z TAFS...
PRECIPITATION CONTINUES TO EDGE EVER SO SLOWLY NORTHEAST. CLOUD
BASES ARE STILL SOLIDLY IN VFR RANGE...BUT EXPECT THE DECK TO
CONTINUE LOWERING TO LOW VFR ALONG AND WEST OF THE
MISSISSIPPI BY DAYBREAK. LIGHT PRECIPITATION COULD BEGIN FALLING
IN SOUTHERN AND WESTERN PORTIONS OF THE CWFA BY 12Z...AND IT WILL
CONTINUE TO SPREAD NORTHEAST AS THE DAY CONTINUES. FORECAST
SOUNDINGS INDICATE A POSSIBLE MIXED BAG OF PRECIPITATION TYPES
ALONG AND NORTH OF THE MISSOURI RIVER...BUT STAYING MOSTLY LIQUID
SOUTH. CIGS WILL FALL INTO MARGINAL RANGES DURING THE LATE MORNING
OR EARLY AFTERNOON...AND CONTINUING DOWN INTO IFR IN THE EVENING
TIME. PRECIPITATION COULD CHANGE BACK AND FORTH FROM LIQUID TO
FROZEN...AND BACK...BUT WILL BE PREDOMINANTLY LIQUID EXCEPT IN FAR
NORTHERN AREAS. AFTER 00Z THE PRECIP WILL LIKELY CHANGE OVER TO
ALL SNOW FROM NORTHWEST TO SOUTHEAST.

CARNEY
&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING
     FOR AUDRAIN-KNOX-LEWIS-LINCOLN-MARION-MONROE-PIKE-RALLS-
     SHELBY.

IL...WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING
     FOR ADAMS IL-BROWN IL-CALHOUN IL-GREENE IL-JERSEY IL-
     MACOUPIN IL-MONTGOMERY IL-PIKE IL.

&&

WFO LSX

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
352 PM CST SUN MAR 19 2006

ILZ058>060-095>099-MOZ018-019-026-027-034>036-042-052-201200-
ADAMS IL-AUDRAIN-BROWN IL-CALHOUN IL-GREENE IL-JERSEY IL-KNOX-
LEWIS-LINCOLN-MACOUPIN IL-MARION-MONROE-MONTGOMERY IL-PIKE-
PIKE IL-RALLS-SHELBY-
352 PM CST SUN MAR 19 2006

...WINTER STORM WATCH IN EFFECT FROM MONDAY AFTERNOON THROUGH
TUESDAY MORNING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL
ILLINOIS AND NORTHEAST MISSOURI.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

LOOK FOR SNOW TO DEVELOP BY MONDAY AFTERNOON AS A MAJOR WINTER
STORM HEADS FOR THE AREA. SNOW MAY MIX WITH SLEET AT TIMES THRU
THE AFTERNOON HOURS. MONDAY NIGHT THE VISIBILITIES WILL DROP TO ONE
QUARTER MILE OR LESS AT TIMES. THE SYSTEM IS EXPECTED TO EXIT BY
LATE TUESDAY...WITH SNOWFALL TOTALS BETWEEN 6 TO 8 INCHES POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. AS THE
EXPECTED WINTER STORM AFFECTS THE AREA ON MONDAY AND TUESDAY...SPOTTERS
ARE ENCOURAGED TO REPORT SNOWFALL TO THE NATIONAL WEATHER SERVICE.

ILZ064-065-069-070-074-100>102-MOZ041-047>051-059>065-201200-
BOND IL-BOONE-CALLAWAY-CLINTON IL-COLE-FAYETTE IL-FRANKLIN-
GASCONADE-JEFFERSON-MADISON IL-MARION IL-MONITEAU-MONROE IL-
MONTGOMERY-OSAGE-ST. CHARLES-ST. CLAIR IL-ST. LOUIS-
ST. LOUIS CITY-WARREN-WASHINGTON IL-
352 PM CST SUN MAR 19 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
ILLINOIS...CENTRAL MISSOURI AND EAST CENTRAL MISSOURI.

.DAY ONE...TONIGHT

A WINTRY MIX OF SNOW...SLEET...AND RAIN IS POSSIBLE AFTER MIDNIGHT
TONIGHT OVER CENTRAL PORTIONS OF MISSOURI...WITH LITTLE OR NO ACCUMULATION
EXPECTED.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THE WINTRY MIX OF SNOW...SLEET...AND RAIN WILL PERSIST ON MONDAY
AS A WINTER STORM MOVES INTO THE AREA. THE PRECIPITATION IS
EXPECTED TO CHANGE TO ALL SNOW MONDAY NIGHT AND THEN TAPER TO
FLURRIES ON TUESDAY...WITH SNOWFALL TOTALS BETWEEN 2 TO 5 INCHES
POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. AS THE
EXPECTED WINTER STORM AFFECTS THE AREA ON MONDAY AND TUESDAY...SPOTTERS
ARE ENCOURAGED TO REPORT SNOWFALL TO THE NATIONAL WEATHER SERVICE.

ILZ079-MOZ072>075-084-085-099-201200-
CRAWFORD-IRON-MADISON-RANDOLPH IL-REYNOLDS-ST. FRANCOIS-
STE. GENEVIEVE-WASHINGTON-
352 PM CST SUN MAR 19 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
ILLINOIS AND SOUTHEAST MISSOURI.

.DAY ONE...TONIGHT

A WINTRY MIX OF SNOW...SLEET...AND RAIN IS POSSIBLE AFTER MIDNIGHT
TONIGHT...WITH LITTLE OR NO ACCUMULATION EXPECTED.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THE WINTRY MIX WILL CHANGE TO ALL RAIN ON MONDAY. THERE IS A
CHANCE FOR THUNDERSTORMS ON MONDAY...DUE TO THE INSTABILITY THAT
WILL EXIST AHEAD OF THE STORM WHEN IT APPROACHES.

THE PRECIPITATION WILL CHANGE BACK TO A WINTRY MIX OF SNOW
...SLEET...AND RAIN MONDAY NIGHT AS A WINTER STORM MOVES INTO THE
AREA. THE PRECIPITATION IS EXPECTED TO CHANGE TO ALL SNOW LATE
MONDAY NIGHT AND THEN TAPER TO FLURRIES ON TUESDAY. LIGHT SNOW
ACCUMULATIONS OF 1 TO 3 INCHES ARE POSSIBLE BY LATE TUESDAY WHEN
THE STORM LEAVES THE AREA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. AS THE
EXPECTED WINTER STORM AFFECTS THE AREA ON MONDAY AND TUESDAY...SPOTTERS
ARE ENCOURAGED TO REPORT SNOWFALL TO THE NATIONAL WEATHER SERVICE.

BYRD