FXUS63 KEAX 232345
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
545 PM CST WED DEC 23 2009
.DISCUSSION...
...SIGNIFICANT WINTER STORM TO AFFECT THE AREA DURING PEAK TRAVEL
TIME THURSDAY AND FRIDAY...
POTENT STORM SYSTEM NOW SHIFTING INTO THE SOUTHERN PLAINS THIS
EVENING...SETTING THE STAGE FOR A HIGH IMPACT EVENT ACROSS PORTIONS
OF EASTERN KANSAS AND WESTERN MISSOURI FOR THE UPCOMING HOLIDAY
TRAVEL.
THIS AFTERNOON AND EVENING...ONGOING SHOWERS/ISOLATED THUNDERSTORMS
SPREADING NORTHWARD ACROSS THE FORECAST AREA. THIS ACTIVITY IS MAINLY
TIED TO HIGHER THETA E AIR MASS WITHIN BROAD ISENTROPIC ASCENT AHEAD OF
EMERGING STORM SYSTEM...AS DIVERGENT EXIT REGION OF ASSOCIATED
80-100KT UPPER JET SPREADS INTO THE MIDWEST. MODEST SHEAR COUPLED WITH
FAIRLY STEEP MID LEVEL LAPSE RATES MAY RESULT IN ISOLATED ROBUST
UPDRAFTS AT TIMES. WHILE SEVERE WEATHER IS NOT EXPECTED...WITH LOW
FREEZING LEVELS IN PLACE...THE STRONGER CONVECTION MAY BE CAPABLE OF
SMALL HAIL.
TONIGHT...AFOREMENTIONED SHORT WAVE TROUGH SLIDES INTO THE SOUTHERN
HIGH PLAINS SENDING PERIODIC VORT MAXES NORTHWARD ACROSS THE AREA.
THIS WILL LIKELY SPELL A FEW ROUNDS OF SHOWERS/ISOLATED THUNDERSTORMS
OVERNIGHT TONIGHT LEADING TO ADDITIONAL RAINFALL WITHIN DRAINAGE BASINS
AND THE POSSIBILITY OF FURTHER RIVER FLOODING. IN ADDITION...AREAS
ACROSS FAR NORTHWEST MISSOURI CURRENTLY SITTING JUST ABOVE THE
FREEZING MARK MAY DIP AT OR SLIGHTLY BELOW FREEZING BY TOMORROW
MORNING LEADING TO ANY PRECIP FALLING AS FREEZING RAIN...LEADING TO
MINOR IMPACTS ON ELEVATED SURFACE.
DOUBLE BARREL PV ANOMALY STRUCTURE WILL TAKE SHAPE THURSDAY AND
THURSDAY NIGHT WITH SOUTHERN STREAM ANOMALY LIFTING ACROSS WESTERN
ARKANSAS INTO CENTRAL MISSOURI AS NORTHERN STREAM ANOMALY DIVES
SOUTHWARD INTO THE CENTRAL PLAINS. AS SOUTHERN STREAM FEATURE LIFTS
NORTHWARD...STRONG HEIGHT FALLS WILL LEAD TO LARGE SCALE ASCENT
OVERSPREADING THE REGION. WIDESPREAD PRECIPITATION IS EXPECTED TO UNFOLD
ACROSS THE FORECAST AREA WITH THE KEY BEING THE TYPE AND INTENSITY AS
THE SYSTEM TRANSITIONS NORTHWARD. BUFR FORECAST SOUNDINGS INDICATING
PRECIP STARTING AS RAIN ACROSS THE ENTIRE AREA OVERNIGHT TONIGHT AND
INTO THE EARLY MORNING HOURS. THIS WILL THEN GRADUALLY TRANSITION TO
A MIX OF RAIN/FREEZING AS SURFACE PRESSURE FALLS DRAW COLDER AIR SOUTHWARD
INTO THE REGION...FROM NORTHWEST TO SOUTHEAST. IN ADDITION...MODELS
INDICATING A FAIRLY IMPRESSIVE TROWAL FEATURE DEVELOPING BY LATE
THURSDAY MORNING AND AFTERNOON. THIS WILL LIKELY LEAD TO PERIODS OF
SLEET DEVELOPING AS WELL...AS WARM NOSE WITHIN THE LOWER ATMOSPHERIC
COLUMN LEADS TO PARTIAL MELTING BEFORE REFREEZING OCCURS CLOSER TO
THE BOUNDARY LAYER.
BY THURSDAY AFTERNOON/NIGHT...A TRANSITION TO ALL SNOW SHOULD TAKE PLACE
FROM NORTHWEST TO SOUTHEAST AS THE COLUMN SUFFICIENTLY COOLS. ONE
CONCERN IS THE HINT OF INITIAL DRY AIR WITHIN THE DENDRITIC GROWTH
ZONE BY THURSDAY AFTERNOON. THIS MAY TEND TO DELAY THE ONSET ON SNOW
AND LEAD TO PERIODS OF FREEZING DRIZZLE OR FREEZING RAIN MIXED WITH
SLEET. SYSTEM BOTTOM OUT AS IT LIFTS INTO NORTHEAST MISSOURI DURING
THE OVERNIGHT PERIODS THURSDAY NIGHT INTO FRIDAY MORNING. THIS
APPEARS TO BE THE MOST FAVORABLE TIME FRAME FOR MODERATE TO HEAVY
SNOW ACROSS THE FORECAST AREA AS STRONG OMEGAS LEAD TO BROAD VERTICAL
ASCENT ACROSS THE AREA. IN ADDITION...SOME INDICATION THAT
AGEOSTROPHIC VERTICAL CIRCULATIONS MAY LEAD TO ENHANCED UPWARD MOTION
AND PERIODS OF HEAVY SNOW. WHILE THE AMOUNT OF TIME FOR HEAVY SNOW TO
OCCUR MAY NOT LAST PARTICULARLY LONG...EASTERN KANSAS/WESTERN
MISSOURI APPEARS TO LIE WITHIN THE PIVOT POINT AS THE SYSTEM DEEPENS
AND LIFTS NORTHWARD INTO EASTERN IOWA. THIS MAY LEAD TO MORE OF A
PROLONGED PERIOD OF LIGHT TO MODERATE SNOWFALL WHICH IS FURTHER
SUPPORTED BY FORECAST SOUNDINGS WHICH KEEP THE COLUMN SUFFICIENTLY
SATURATED HEADING INTO FRIDAY MORNING. THEREFORE...THINKING SNOW
TOTALS SHOULD BE HIGHEST ALONG AND NORTH OF A BLUE MOUND KANSAS TO
UNIONVILLE MISSOURI LINE WHERE 6+ INCHES WILL BE POSSIBLE BY THE TIME
THE EVENT IS THROUGH. FURTHER SOUTH AND EAST...THE LONGEVITY OF THE
INITIAL WARM AIR AND SUBSEQUENT SLOWER TRANSITION TO SNOW MAY LIMIT
ACCUMULATIONS. HOWEVER...WITH MIXED PRECIP LIKELY ACROSS MOST
LOCATIONS...HAZARDOUS TRAVEL CONDITIONS WILL CERTAINLY EXIST. FOR NOW
WILL UPGRADE THE WINTER STORM WATCH TO A WINTER STORM WARNING ALONG
AND WEST OF A BUTLER TO GRANT CITY LINE WHERE THE ONSET OF WINTRY
PRECIP WILL OCCUR FIRST. AREAS FURTHER EAST MAY NEED TO BE UPGRADED
AS WELL OR INCLUDED IN A WINTER WEATHER ADVISORY IN THE NEAR FUTURE.
NORTHER STREAM PV ANOMALY DIVES SOUTH AND WRAPS INTO THE OVERALL
UPPER CIRCULATION BY FRIDAY WITH THE SYSTEM BECOMING MORE BAROTROPIC
WITH TIME. WRAP AROUND MOISTURE WILL CONTINUE THROUGH THE DAY FRIDAY
WITH SNOW SHOWERS LIKELY LEADING TO ADDITIONAL LIGHT ACCUMULATIONS.
OTHERWISE...COLDER AIR WILL CONTINUE TO FILTER SOUTH HEADING INTO
THE WEEKEND WITH LOWS DIPPING INTO THE TEENS ACROSS MOST LOCATIONS BY
FRIDAY NIGHT/SATURDAY MORNING...LIKELY COLDER OVER SNOW PACKED AREAS.
DEROCHE
MEDIUM RANGE (SATURDAY THROUGH WEDNESDAY)...
BY THE TIME THE WEEKEND ARRIVES OUR WINTER WEATHER STORM WILL BE
COMING TO AN END...BUT WILL NOT HAVE COMPLETELY EXITED THE REGION
YET. MID RANGE DETERMINISTIC AND ENSEMBLE RUNS ARE ALL IN REASONABLE
AGREEMENT THAT THIS WEEKS WINTER STORM SYSTEM WILL BE LIFTING
TOWARDS THE LOWER GREAT LAKES SATURDAY. HOWEVER...LATEST RUNS HAVE
SLOWED THE EXIT OF THE SYSTEM...WHICH SEEMS REASONABLE GIVEN THE
STRONG JET STREAK THAT WILL BE DIGGING DOWN THE BACKSIDE OF THE
UPPER LEVEL CUTOFF LOW LATE IN THE WORK WEEK. HAVE DELAYED THE EXIT
OF OUR CHANCE SNOW POPS FOR SATURDAY AS A RESULT. THOUGHTS ARE THAT
ONLY MINOR ADDITIONAL ACCUMULATIONS WILL OCCUR WITH SOME LIGHT SNOW
SHOWERS ACROSS NORTH CENTRAL AND NORTHEAST MISSOURI IN THE WRAP
AROUND ACTIVITY...WITH FLURRIES FARTHER WEST AND SOUTH. SUNDAY MAY
STILL SEE FLURRIES ALONG THE IOWA BORDER...BUT REMAINDER OF THE
FORECAST /THROUGH WEDNESDAY/ IS CURRENTLY DRY.
TEMPERATURE WISE...BY SUNDAY THE SPLIT FLOW AROUND THE RIDGE OVER
THE WESTERN CONUS WILL HAVE RETURNED TO DOMINANCE ACROSS THE CENTRAL
PLAINS...WITH OUR LITTLE SLICE OF THE REGION STUCK BETWEEN THE
NORTHERN AND SOUTHERN WESTERLY STREAMS. SURFACE AND UPPER LEVEL
WINDS WILL PREVAIL FROM THE NORTHWEST...SO COLD CANADIAN AIR WILL
HAVE NO PROBLEMS FILTERING SOUTH THROUGH THE FIRST HALF OF NEXT WORK
WEEK. HAVE HEDGED GOING FORECAST NUMBERS A LITTLE LOWER AS A
RESULT...TOWARDS THE ENSEMBLE LOW GUIDANCE VALUES FOR THE WEEKEND
AND ENSEMBLE MEAN VALUES FOR NEXT WORK WEEK.
CUTTER
&&
.AVIATION...
FOR THE 18Z TAF CYCLE...A NARROW LINE OR CLUSTER OF THUNDERSTORMS
MOVING NORTHEAST IN BETWEEN KMCI AND KMKC TERMINALS. BASED ON
UPSTREAM OBSERVATIONS...CURRENT TREND OF IFR CIGS WILL
CONTINUE...BUT VISIBILITIES WILL INCREASE FROM LIFR TO IFR CATEGORY.
THREAT OF CONVECTION IS SHORT-LIVED...AND EXPECT THREAT OF TSRA TO
END IN THE 19-20Z TIMEFRAME. A PERIOD OF LIGHT TO MODERATE RAIN
WITH IFR CIGS/VSBYS WILL CONTINUE FOR THE THROUGH
MID-AFTERNOON...THEN ALL TERMINALS SHOULD EXPERIENCE A BRIEF LULL IN
PRECIPITATION AS SHORTWAVE PASSAGE WILL BRING SUBSIDENCE...THUS
PRECIPITATION WILL TREND TOWARD DRIZZLE. A PERSISTENT PERIOD OF
MODERATE RAIN AND IFR CIGS/VSBYS WILL REDEVELOP BY 02-04Z AS ANOTHER
SHORTWAVE FEATURE ENHANCES BROADSCALE ISENTROPIC LIFT. PRECIPITATION
WILL CONTINUE INTO THE MORNING HOURS OF THE 24TH...WITH FORECAST
SOUNDINGS INDICATING SLEET MIXING WITH RAIN BY 16-17Z AT KMKC AND
KMCI...AND SNOW AT KSTJ. CIGS/VSESULT IN ABAND OF HEAVIER RAIN
MOVING NORTHEAST ACROSS T
SF
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY
AFTERNOON FOR MOZ005>008-014>017-022>025-030>033-038>040-
044>046-054.
WINTER STORM WARNING FROM 3 PM THURSDAY TO 6 PM CST FRIDAY FOR
MOZ003-004-013-021-028-029-037-043-053.
WINTER STORM WARNING FROM 9 AM THURSDAY TO 6 PM CST FRIDAY FOR
MOZ001-002-011-012-020.
KS...WINTER STORM WARNING FROM 3 PM THURSDAY TO 6 PM CST FRIDAY FOR
KSZ057-060-103>105.
WINTER STORM WARNING FROM 9 AM THURSDAY TO 6 PM CST FRIDAY FOR
KSZ025-102.
&&
$$
