FXUS63 KEAX 241106
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
505 AM CST THU DEC 24 2009
.DISCUSSION...
...SIGNIFICANT WINTER STORM TO AFFECT THE AREA DURING PEAK TRAVEL
TIME TODAY THROUGH FRIDAY...
POTENT STORM SYSTEM NOW SHIFTING INTO THE SOUTHERN PLAINS THIS
MORNING...SETTING THE STAGE FOR A HIGH IMPACT EVENT ACROSS PORTIONS
OF EASTERN KANSAS AND MISSOURI FOR THE UPCOMING HOLIDAY TRAVEL.
DISTINCT PV ANOMALY AND WELL DEFINED WAVE NOW ENTERING THE SRN TEXAS
PANHANDLE...WITH A CLASSIC BAROCLINIC LEAF STRUCTURE BLOSSOMING
THROUGH THE SRN PLAINS. WELL IN ADVANCE OF THIS FEATURE...DEEP
CONVECTION HAS BEEN SUSTAINED BY AN INFLUX OF HIGH MOISTURE AND LLJ
AXIS...WHILE ADDITIONAL ELEVATED CONVECTION HAS ERUPTED CLOSER TO
THE COLD CORE ALOFT IN SRN OKLAHOMA...AND ACTUALLY IS PASSING ACROSS
THE FRONTAL BOUNDARY INTO NEAR FREEZING SFC AIR. STRONGER JET AXIS
ENTERING CNTRL TEXAS NOW BEGINNING TO SHOW SIGNS OF CURVATURE TO THE
NORTH...WHICH WILL EVENTUALLY GUIDE THIS PV ANOMALY INTO CNTRL
MISSOURI LATER TONIGHT. SECONDARY PV ANOMALY DIVING SOUTH THROUGH
THE NRN ROCKIES WILL INTERACT WITH THE SRN STREAM ANOMALY THROUGH
THE NEXT 48 HOURS...ALL OF WHICH WILL CREATE A VERITABLE POTPOURRI
OF WINTER WEATHER ACROSS THE FORECAST AREA.
INVERTED SFC TROUGH HAS PROGRESSED TO NEAR A NEVADA TO LAMONI LINE
EARLY THIS MORNING...WITH A SHARPENING TEMPERATURE AND DEWPOINT
GRADIENT ABOUT THIS BOUNDARY. SUBFREEZING AIR WAS LAGGING THE TROUGH
SOMEWHAT...AND WAS NOW ENTERING FAR NORTHWEST MISSOURI.
HOWEVER...SURGE OF MUCH COLDER AIR ASSOCIATED WITH THE NRN STREAM
WAVE WAS RACING SOUTHEAST THROUGH CNTRL NEBRASKA...AND WILL BEGIN TO
REACH THE INVERTED TROUGH AXIS BISECTING THE CWA THIS
AFTERNOON...CREATING ENHANCED LOW LEVEL BAROCLINICITY AND SETTING
THE STAGE FOR EXPLOSIVE CYCLOGENESIS OVER ERN MISSOURI LATER TODAY.
SOME MINOR INITIALIZATION ERRORS WERE APPARENT ON 00Z MODEL
RUNS...THOUGH RECTIFIED ON SUBSEQUENT 06Z RUNS...CREATING SMALL
DISCREPANCIES IN THE POSITION AND INTENSITY OF THE MOST PREFERRED
DEFORMATION BANDING AND TROWAL POSITION.
MERIDIONAL COMPONENT TO THE FLOW ALOFT CAN BE SEEN ON REGIONAL RADAR
IMAGERY...AND AS ANOMALY CENTER MAKES THE TURN TO THE NORTH AND
STRONGER CYCLOGENESIS COMMENCES...MORE AGGRESSIVE TROWAL DEVELOPMENT
WILL OCCUR A TOP A DEEPENING COLD BOUNDARY LAYER WEST OF THE
INVERTED TROUGH AXIS. THUS...WITH STRONG SUPPORT FROM MODEL
SOUNDINGS AND PARTIAL THICKNESS METHODS...SLEET LOOKS TO BECOME THE
PREDOMINANT PRECIPITATION TYPE ALONG THE I-35 CORRIDOR BY THE EARLY
AFTERNOON HOURS. STRONG UVV COINCIDENT WITH MARGINALLY FAVORABLE
MIDLEVEL LAPSE RATES ALSO SUGGEST THE POSSIBLE FOR THUNDER WITHIN
THESE BANDS OF SLEET (ENHANCING THE PRECIPITATION RATE AS WELL).
EASTERN CWA MAY WELL SEE ENTIRELY LIQUID (REMAINING EAST OF THE
INVERTED TROUGH) THROUGH THE LATE AFTERNOON...AS SFC LOW DEEPENING
ACTS TO HELP STALL THE EWD PROGRESSION OF THE TROUGH...ALONG WHICH
THE BAROCLINICITY TIGHTENS.
SOMEWHAT PROBLEMATIC IN MODEL SOLUTIONS IS THE PERIODIC INTRODUCTION
OF DRY AIR ALOFT...LIMITING PRECIPITATION PROCESSES...AND ESPECIALLY
DENDRITIC GROWTH. IT IS UNCERTAIN WHETHER THIS IS OCCURRING BECAUSE
OF CONVECTIVE RESPONSE AND SUBSIDENCE...OR INTRODUCTION OF DRIER AIR
FROM THE NORTHWARD CURVING TEXAS JET...OR EVEN AN AIR STREAM
UNDERCUTTING FROM THE NRN PV ANOMALY. REGARDLESS...NAM-WRF FORECASTS
HAVE LATCHED ONTO THE EXTENDED PRESENCE OF THIS DRY AIR...WITH THE
GFS ALSO PRESENTING SIMILAR EVIDENCE (LOCALLY LIMITING QPF TOTALS).
FEEL WHILE THERE WILL BE SOME DRY AIR PRESENT...THIS WILL BE MORE OF
A TRANSIENT FEATURE...MATCH CLOSER TO A CONCEPTUAL MODEL OF A
MATURING DEEP MIDLATITUDE CYCLONE.
CHANGE OVER TO COMPLETELY SNOW SHOULD OCCUR ALONG THE STATE LINE
SOMETIME IN THE LATE AFTERNOON OR EARLY EVENING...WITH ONLY A SLOW
EWD PROGRESSION INTO CNTRL AND NERN MISSOURI TONIGHT. AS TROWAL
DEVELOPMENT BECOMES QUITE INTENSE...A SIGNIFICANT INFLUX OF WARM AIR
IN THE H8-H7 LAYER MAY BE MAINTAINED THROUGH THE ERN CWA FOR MUCH OF
THE EVENING. HAVE SIGNIFICANT CONCERNS FOR SUBSTANTIAL SLEET
ACCUMULATIONS ACROSS THE ERN HALF OF THE CWA...AND HAVE EXPANDED THE
WINTER STORM WARNING FOR THE ENTIRE AREA. LOCATIONS OF THE HEAVIEST
SNOW IS VERY DIFFICULT TO PINPOINT AT THIS TIME...BECOMING HIGHLY
DEPENDENT ON THE EXACT POSITION AND FORMATION OF THE EXPECTED
DEFORMATION BAND. MOST PREFERRED LOCATION WOULD BE FROM SERN KANSAS
TO NORTH CENTRAL MISSOURI...EAST OF THE I-35 CORRIDOR...THOUGH GIVEN
THE EXPANSE OF THE ENTIRE STORM SYSTEM...JUST ABOUT EVERYONE CAN
EXPECT SOME SNOW AND SLEET...AND HORRIBLE TRAVEL CONDITIONS FOR THE
HOLIDAY.
CONSOLIDATION OF THE PV ANOMALIES WILL OCCUR FRIDAY THROUGH
SATURDAY...KEEPING MUCH OF THE AREA IN SATURATED CYCLONIC FLOW.
WINDS WILL BE QUITE PROBLEMATIC WITH RESPECT TO BLOWING AND DRIFTING
SNOW...AS WELL AS REDUCED VISIBILITIES. MAY NEED TO EXTEND WARNING
OUT THROUGH SATURDAY FOR ADDITIONAL LIGHT SNOW AND BLOWING SNOW
EFFECTS. WITH THE ENTIRE COLUMN QUITE COLD BY FRIDAY AFTERNOON...AND
SNOW SHOWER ACTIVITY WILL BECOME QUITE EFFICIENT WITH SLR EASILY
BETTER THAN 15:1. AS SUCH...SEVERAL MORE INCHES OF LIGHT FLUFFY SNOW
IS VERY LIKELY ACROSS THE NRN CWA FRIDAY AFTERNOON THROUGH SATURDAY.
21
&&
.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/RESULT IN A BAND OF HEAVIER RAIN
MOVING NORTHEAST.
SF
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST
FRIDAY FOR MOZ007-008-016-017-024-025-032-033-039-040-045-046.
WINTER STORM WARNING FROM 3 PM THIS AFTERNOON TO 6 PM CST
FRIDAY FOR MOZ006-015-023-031-038-044-054.
WINTER STORM WARNING FROM NOON TODAY TO 6 PM CST FRIDAY FOR
MOZ005-014-022-029-030-037-043-053.
WINTER STORM WARNING FROM 9 AM THIS MORNING TO 6 PM CST FRIDAY
FOR MOZ003-004-013-020-021-028.
WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR MOZ001-002-011-
012.
KS...WINTER STORM WARNING FROM 9 AM THIS MORNING TO 6 PM CST FRIDAY
FOR KSZ025-057-060-103>105.
WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR KSZ102.
&&
$$
