Hail and Damaging Winds in Missouri, March 22, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1235 PM CDT TUE MAR 22 2011

...UPDATED AVIATION DISCUSSION...

.DISCUSSION...

SHORT TERM (TONIGHT-THURSDAY)...

POWERFUL MID LEVEL TROUGH EXTENDING FROM SE IDAHO INTO THE GREAT
BASIN WILL BE THE MAIN FORECAST CHALLENGE AS THIS FEATURE SHIFTS
INTO THE PLAINS BY EARLY THIS EVENING. AHEAD OF THIS FEATURE...A
BROAD WARM SECTOR EXTENDS SOUTH OF STRONG WARM FRONT THAT HAS
LIFTED TO NEAR I-80. DESPITE UNSEASONABLY MILD AIR EARLY THIS
MORNING ACROSS THE REGION...HIGH PRESSURE OVER THE GULF AND RECYCLED
CONTINENTAL AIR HAS MAINTAINED DEWPOINTS IN THE UPPER 50S AND NO
CHANGE TO THIS HOMOGENEOUS AIRMASS IS EXPECTED TODAY.

00Z SOUNDINGS SHOW A PRONOUNCED ELEVATED MIXED LAYER ACROSS THE
PLAINS THAT WILL HOLD FOR MUCH OF THE DAY WITH VERY WARM
TEMPERATURES AGAIN EXPECTED THROUGH FILTERED SUNSHINE AND GUSTY
SOUTH WINDS. EXPECT THE REGION TO BE GENERALLY PRECIPITATION FREE
THROUGH LATE AFTERNOON...WITH JUST A SLIGHT CHANCE THAT ISENTROPIC
ASCENT GENERATED BY A WEAK WARM ADVECTION WING COULD YIELD A BAND OF
ELEVATED CONVECTION EARLY THIS AFTERNOON.

HI RESOLUTION MODEL OUTPUT PLACE A MODIFIED PACIFIC DRYLINE/
PRE-FRONTAL TROUGH ALONG THE KS/MO BORDER AROUND 00Z...EXTENDING
SOUTH FROM A SFC LOW AND TRIPLE POINT OVER WRN IOWA. POINT FORECAST
SOUNDINGS BRING UP SEVERAL CONCERNS WITH RESPECT TO THE POTENTIAL
FOR DEEP MOIST CONVECTION ACROSS THE CWA EARLY THIS EVENING...
INCLUDING LIMITED MOISTURE DEPTH AND POOR MID LEVEL LAPSE RATES. IN
THE PRESENCE OF VERY STRONG DEEP LAYER SHEAR...BUOYANCY POTENTIAL
SEEMS GREATLY UNDERWHELMED WHICH COULD LEAD TO UPDRAFTS BEING
SHEARED APART ESPECIALLY IN AREAS AWAY FROM STRONGLY FORCED ASCENT.
BOUNDARY LAYER FLOW WILL ALSO TEND TO VEER WITH TIME AS THE SURFACE
LOW REACHES MATURITY BY MID AFTERNOON ALONG WITH A NORTHEASTERLY
MOVEMENT THAT WILL MAINTAIN ONLY A SMALL CORRIDOR OF PRESSURE FALLS
ACROSS IOWA INTO EXTREME NW MO. IT IS NOT SURPRISING THAT THE 00Z
NAM-WRF ALONG WITH SEVERAL CONVECTION ALLOWING RUNS LIKE THE 00Z
NSSL WRF GENERATE NO DEEP MOIST CONVECTION OUTSIDE OF A NARROW ARC
AHEAD OF THE TRIPLE POINT.

BASED ON CURRENT DATA...THINK A NARROW WINDOW OF OPPORTUNITY FOR
SEVERE WEATHER EXISTS ACROSS FAR NW MO AND FAR NE KS BETWEEN 23Z AND
03Z WHERE PARAMETERS ARE MAXIMIZED CLOSEST TO THE SFC LOW. WEAKER
FORCING FOR ASCENT WOULD TEND TO LIMIT THE COVERAGE OF CONVECTION
FURTHER SOUTH TO SCATTERED AT BEST (MORE LIKELY ISOLATED). FOR ANY
STORMS THAT DO DEVELOP...STRONG DEEP LAYER SHEAR LARGELY NORMAL TO
THE DRYLINE WOULD LIKELY YIELD DISCRETE SUPERCELLS WITH A FAVORABLE
MOVEMENT OFF THE BOUNDARY INTO THE WARM SECTOR. MID LEVEL LAPSE RATE
ISSUES WOULD TEND TO KEEP HAIL SIZE OUT OF THE DESTRUCTIVE
CATEGORY...WITH WIND THE PRIMARY THREAT. LOW LEVEL HODOGRAPHS ARE
CERTAINLY IMPRESSIVE TOWARD THE IOWA BORDER...SO A TORNADO THREAT
CANNOT BE DISCOUNTED IN THE NWRN CWA DESPITE MARGINAL LCL HEIGHTS.
AS 850MB FLOW QUICKLY VEERS AFTER DARK...ANY STORMS THAT DO MANAGE
TO FIRE ALONG THE SOUTHWARD EXTENSION OF THE DRYLINE SHOULD RAPIDLY
DISSIPATE FROM SOUTH TO NORTH AS THE BOUNDARY LAYER BECOMES
RE-CAPPED AND MOISTURE IS SCOURED.

STRONG COLD ADVECTION WILL BRING US BACK TO REALITY FOR THE NEXT
COUPLE OF DAYS WITH HIGHS SOME 15 DEGREES COLDER WEDNESDAY AND
ANOTHER 10 DEGREES COLDER STILL THURSDAY WITH HIGHS IN THE MID 40S
TO LOW 50S. DRY WEATHER IS EXPECTED BOTH DAYS. A QUICK SWING OF
EVENTS WILL TAKE SHAPE THURSDAY NIGHT AS SURFACE AND SHORTWAVE
RIDGING ALOFT BOTH SHIFT EAST ALLOWING FOR A RAPID SURGE OF
WARM/MOIST AIR BACK INTO THE REGION ABOVE THE SHALLOW COLD SURFACE
LAYER. EXPECT PRECIPITATION TO BREAK OUT QUICKLY BY DAYBREAK
FRIDAY...WITH SURFACE CONDITIONS RIGHT NOW WARM ENOUGH FOR JUST A
COLD RAIN.

BOOKBINDER

MEDIUM RANGE (FRIDAY THROUGH MONDAY)...

VERY LOW CONFIDENCE THROUGHOUT MOST OF THE MEDIUM RANGE PERIOD...AS
OPERATIONAL AND ENSEMBLE MEMBERS CONTINUE TO DISPLAY SIGNIFICANT
SPREAD IN THEIR RESPECTIVE SOLUTIONS. WHILE A GENERAL OMEGA TYPE
PATTERN OVER THE WRN HEMISPHERE IS RATHER WELL AGREED UPON BY MODELS
(FEATURING HIGHLY AMPLIFIED FLOW AND STRONG POSITIVE HEIGHT
ANOMALIES GREATER THAN 2 NORMALIZED STANDARD DEVIATIONS SITUATED
OVER THE NUNAVUT ARCHIPELAGO)...THE PROGRESSION AND STRENGTH OF
WAVES IN THE SRN STREAM UNDERCUTTING THE AFOREMENTIONED RIDGE (AND
INTERACTION WITH ENHANCED BAROCLINICITY THROUGH THE REGION) LEADS TO
NUMERICAL GUIDANCE SPREADS IN EXCESS OF 20F...AND LARGE QUESTIONS AS
TO THE TIMING AND PHASE OF PRECIPITATION AFFECTING THE FORECAST
AREA. LITTLE TO NO MODEL RUN TO RUN CONTINUITY ONLY EXACERBATES THE
UNCERTAINTY...WITH 00Z ECMWF NOW MATCHING THE ENSEMBLE MAJORITY
VERSUS THE 00Z OPERATIONAL GFS (OPPOSITE OF LAST NIGHTS 00Z
SOLUTIONS).

GIVEN THE OVERALL PATTERN AND PROCLIVITY FOR AMPLIFIED RIDGING OVER
CNTRL CANADA TO PROMOTE PERSISTENT SFC PRESSURE RISES IN THE GREAT
LAKES AND UPPER MIDWEST...HAVE TRENDED TEMPERATURES TOWARDS THE
COLDER END OF THE GUIDANCE SPECTRUM. HAVE KEPT THE FORECAST LARGELY
AROUND 1 SIGMA LEVEL BELOW AVERAGE...AS FREQUENT DENSE CLOUD COVER
MAY ACTUALLY NARROW THE DIURNAL SPREAD AND KEEP OVERNIGHT LOWS FROM
FALLING MORE THAN OTHERWISE WOULD BE EXPECTED. OBVIOUS CAVEAT IS
ANY NIGHTTIME PERIOD WITH CLEARING SKIES AND PRESSURE RIDGING
BUILDING SOUTH WOULD BE IN THE MUCH BELOW NORMAL CATEGORY.

OTHERWISE...WITH SUCH A SPREAD IN SHORTWAVE TIMING AND
INTENSITY...LOW POPS WERE SPREAD THROUGH A MUCH LONGER TIME FRAME
THAN NORMALLY WOULD BE DESIRED. IN REALITY...THERE WILL BE PERIODS
WHERE PRECIPITATION CHANCES WILL NEED TO BE ADVERTISED EVEN
STRONGER...AND THOSE PERIODS WHERE DRIER AIR DOMINATES THE
ATMOSPHERIC COLUMN. PRECIPITATION PHASE ALSO REMAINS IN HIGH
UNCERTAINTY...WITH PARTIAL THICKNESS METHODS FROM BOTH THE GFS AND
ECMWF SUGGESTING PERIODS WITH MIXED WINTRY PRECIPITATION...IF NOT
ENTIRELY SNOW FOR CERTAIN PERIODS LATER IN THE WEEKEND AND EARLY
NEXT WEEK. CERTAINLY...ANY DEEPER AND MORE DEFINED SHORTWAVE WOULD
PROMOTE DEFORMATION AND FRONTOGENETICAL BANDING WITHIN THE NORTHWEST
SECTOR OF THE CYCLONE...THOUGH GIVEN THE TIME OF YEAR...IT BECOMES
SOMEWHAT MORE DIFFICULT TO ACHIEVE THESE PROCESSES.
NEVERTHELESS...THE CHANCE DOES EXIST AND IS CERTAINLY NOT WITHOUT
PRECEDENT (EVEN ALL THE WAY INTO THE MIDDLE OF APRIL FOR THAT
MATTER).

21

&&

.AVIATION...

FOR THE 18Z TAFS...MARGINAL MVFR CEILINGS ARE BEGINNING TO SPREAD
INTO THE TERMINALS EARLY THIS AFTERNOON. ALREADY GUSTY SOUTHWEST
WINDS MAY INCREASE IN THE LATE AFTERNOON/EARLY EVENING HOURS AS
SKIES CLEAR NEAR THE APPROACHING DRY-LINE AND DEEPER LAYER MIXING
OCCURS. SPEAKING OF THE DRY-LINE...STORMS ARE EXPECTED TO FIRE UP IN
NORTHEASTERN KANSAS AND SOUTHEASTERN NEBRASKA LATE THIS
AFTERNOON...AND QUICKLY MOVE EAST. WINDOW OF OPPORTUNITY FOR STORMS
AT THE TERMINALS LOOKS TO BE VERY NARROW...LIMITED TO BETWEEN 22Z AND
01Z. THE KSTJ TERMINAL HAS THE BEST POTENTIAL TO SEE STORMS...BUT
HAVE INCLUDED VCTS FOR THE KANSAS CITY TERMINALS. A COLD FRONT WILL
THEN CLEAR ANY STORMY ACTIVITY OUT FROM WEST TO EAST TONIGHT...WITH A
GUSTY NORTHWEST WIND THEN EXPECTED TO SPREAD ACROSS THE REGION
WEDNESDAY MORNING.

CUTTER

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

WFO EAX

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
510 AM CDT TUE MAR 22 2011

KSZ025-057-060-102>105-MOZ001>008-011>017-020>025-028>033-037>040-
043>046-053-054-221800-
ATCHISON KS-MIAMI-LINN KS-DONIPHAN-LEAVENWORTH-WYANDOTTE-JOHNSON KS-
ATCHISON MO-NODAWAY-WORTH-GENTRY-HARRISON-MERCER-PUTNAM-SCHUYLER-
HOLT-ANDREW-DE KALB-DAVIESS-GRUNDY-SULLIVAN-ADAIR-BUCHANAN-CLINTON-
CALDWELL-LIVINGSTON-LINN MO-MACON-PLATTE-CLAY-RAY-CARROLL-CHARITON-
RANDOLPH-JACKSON-LAFAYETTE-SALINE-HOWARD-CASS-JOHNSON MO-PETTIS-
COOPER-BATES-HENRY-
510 AM CDT TUE MAR 22 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHWEST...NORTH CENTRAL AND
WEST CENTRAL MISSOURI...AS WELL AS EXTREME EASTERN KANSAS.

.DAY ONE...TODAY AND TONIGHT

 A POTENTIALLY ACTIVE SEVERE WEATHER DAY IS EXPECTED ACROSS THE
 REGION AS A POTENT STORM SYSTEM MOVES INTO THE PLAINS LATER
 THIS AFTERNOON. A WARM AND SEASONABLY MOIST AIRMASS WILL PERSIST
 TODAY AHEAD OF A DRYLINE THAT WILL APPROACH THE KANSAS AND
 MISSOURI BORDER LATE THIS AFTERNOON. CONDITIONS APPEAR FAVORABLE
 FOR THE DEVELOPMENT OF SCATTERED SEVERE THUNDERSTORMS AHEAD OF THE
 DRYLINE...WITH THESE STORMS IMPACTING WESTERN MISSOURI AND EASTERN
 KANSAS BETWEEN 6  AND 10 PM.

 MODERATE INSTABILITY AND VERY STRONG VERTICAL WIND SHEAR WILL
 SUPPORT THE DEVELOPMENT OF SCATTERED SUPERCELL THUNDERSTORMS WITH
 THE POTENTIAL FOR UP TO GOLF BALL SIZE HAIL AND DAMAGING WIND
 GUSTS. ISOLATED TORNADOES WILL ALSO BE POSSIBLE...WITH THE GREATEST
 THREAT TOWARD THE IOWA AND NEBRASKA BORDERS.

 THUNDERSTORMS WILL GRADUALLY DIMINISH IN INTENSITY AND COVERAGE
 BY MID EVENING AS THEY SHIFT INTO CENTRAL AND NORTH CENTRAL
 MISSOURI.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

 IN THE WAKE OF A COLD FRONT LATE TONIGHT...GUSTY NORTHWEST WINDS
 WILL USHER IN DRIER AIR INTO THE REGION. AS TEMPERATURES WARM
 BACK INTO THE 60S...THIS MAY LEAD TO A HEIGHTENED FIRE DANGER
 ACROSS CENTRAL MISSOURI WEDNESDAY AFTERNOON.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE THIS AFTERNOON AND EARLY THIS
EVENING...ESPECIALLY WEST OF A CHILLICOTHE TO WARRENSBURG LINE.

BOOKBINDER