Severe Thunderstorm Warning 203, NWS Memphis, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
412 PM CDT MON MAY 17 2010

.DISCUSSION...

ISOLATED STRONG TO SEVERE THUNDERSTORM POTENTIAL LATE THIS
AFTERNOON AND EARLY THIS EVENING IS THE FIRST CONCERN. THE NEXT
CONCERN IS SEVERE THUNDERSTORM...HEAVY RAINFALL...AND FLOODING
POTENTIAL WEDNESDAY NIGHT THROUGH FRIDAY.

LATEST MODELS WERE IN FAIR AGREEMENT. USED A BLEND WITH A SLIGHT
PREFERENCE TOWARDS THE 15Z SREF MODEL.

THE BIGGEST CHANGES WERE TO ADD LOW RAIN CHANCES EARLY THIS
EVENING ACROSS THE AREA...AND INCREASED RAIN CHANCES WEDNESDAY
NIGHT THROUGH FRIDAY.

AT 4 PM CDT ACROSS THE MIDSOUTH AND FORECAST AREA...PARTLY SUNNY
CONDITIONS WERE OCCURRING. ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS WERE OCCURRING MAINLY NORTH OF I-40. A WEAK SURFACE
TROUGH WAS NEAR THE ARKANSAS/MISSOURI AND TENNESSEE/KENTUCKY STATE
LINES AND A MID/UPPER LOW WAS OVER ILLINOIS.

THROUGH 10 PM...EXPECT ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS OVER THE AREA AS THE AIR REMAINS MOIST AND UNSTABLE
SOUTH OF THE MID/UPPER LOW. KEPT RAIN CHANCES IN THE 20 TO 50
PERCENT RANGE. WITH COLD MID LEVEL TEMPERATURES...500 MB -13 TO
-16C...AND LOW WET BULB HEIGHTS AROUND 7000-9000 FT AGL...A FEW
STORMS MAY CONTAIN HAIL...POSSIBLY SEVERE UP TO HALF DOLLARS.
ENVIRONMENTAL SHEAR OF 30 TO 45 KTS SUPPORT SPITTING CELLS WITH
THE LEFT MOVERS HAVING THE BEST POTENTIAL FOR LARGE HAIL. THINK
CONVECTION WILL REMAIN FAIRLY UNORGANIZED...SO DOUBT A SEVERE
THUNDERSTORM WATCH WOULD BE NEEDED. GUSTY WINDS AND LOCALLY HEAVY
DOWNPOURS ARE POSSIBLE AS WELL. ACTIVITY WILL DIMINISH 8 TO 10 PM
WITH THE LOSS OF DAYTIME HEATING.

AFTER 10 PM TONIGHT...RAINFREE AND COOLER CONDITIONS CAN BE
EXPECTED AS SURFACE WINDS SWITCH TO THE NORTHWEST. SOME CLEARING
CAN BE EXPECTED. 12Z MAVMOS LOWS IN THE 50S APPEARED REASONABLE.
WOULD NOT BE COMPLETELY SURPRISED IF PATCHY FOG DEVELOPED WHERE
RAIN OCCURS THIS AFTERNOON...BUT LEFT MENTION OUT WITH LOW
CONFIDENCE.

TUESDAY WILL BE A MOSTLY SUNNY AND PLEASANT DAY WITH HIGHS IN THE
MID TO UPPER 70S. TUESDAY NIGHT WILL BE RAINFREE AND COOL WITH
LOWS MAINLY IN THE 50S. USED A BLEND OF MODEL GUIDANCE FOR
TEMPERATURES.

WEDNESDAY...CLOUDS WILL BE ON THE INCREASE WEST TO EAST. KEPT LOW
CHANCES FOR AFTERNOON SHOWERS AND STORMS WEST OF I-55...BUT THINK
BETTER RAIN CHANCES WILL HOLD OFF UNTIL WEDNESDAY NIGHT.

WEDNESDAY NIGHT THROUGH FRIDAY...SEVERE THUNDERSTORM...HEAVY
RAINFALL...AND FLASH FLOODING POTENTIAL APPEARS TO BE INCREASING.
LATEST MODELS HAVE BEEN HINTING AT STRONG SHEAR...30-50 KTS...AND
A VERY UNSTABLE AIRMASS DEVELOPING WITH A STRONG PRESSURE
DISTURBANCE MOVING THROUGH THE AREA. APPEARS SCATTERED TO
NUMEROUS SHOWERS AND THUNDERSTORMS WILL DEVELOP ALONG A WARM FRONT
WEDNESDAY NIGHT INTO EARLY THURSDAY WHICH WOULD HAVE THE HIGHEST
HEAVY RAINFALL AND FLOODING POTENTIAL AS A STRONG LOW LEVEL JET
AND HIGH PRECIPITABLE WATER VALUES MAY PRODUCE SEVERAL INCHES OF
RAINFALL SOMEWHERE OVER THE AREA...PROBABLY NORTH OF I-40. SEVERE
THUNDERSTORMS MAY BE POSSIBLE AS WELL WEDNESDAY NIGHT INTO EARLY
THURSDAY...BUT THINK THE BETTER SHOT WILL OCCUR THURSDAY AFTERNOON
THROUGH FRIDAY ONCE WARM FRONT SURGES NORTH OF THE AREA. LARGE
HAIL AND DAMAGING WINDS WOULD BE THE MAIN SEVERE STORM HAZARDS...
THOUGH SHEAR MAY BE STRONG ENOUGH FOR TORNADOES. FOR NOW...INCREASED
RAIN CHANCES DURING THIS TIME FRAME. WILL CLOSELY MONITOR THIS
POSSIBLE HIGH IMPACT WEATHER EVENT.

FRIDAY NIGHT THROUGH NEXT MONDAY...MAINLY RAINFREE AND VERY WARM
CONDITIONS ARE EXPECTED AS MID/UPPER RIDGE OF HIGH PRESSURE BUILDS
INTO THE AREA. HIGHS WILL PROBABLY BE AROUND 90 AND LOWS 65 TO
70...ROUGHLY 10 DEGREES ABOVE AVERAGE. WITH VERY WARM/UNSTABLE
AIR...A FEW AFTERNOON/EVENING THUNDERSTORMS MAY BE POSSIBLE...BUT
THINK CHANCES FOR RAIN REMAIN TOO LOW TO ADD LOW CHANCE FOR
SHOWERS/STORMS AT THIS TIME...ESPECIALLY WITH VERY WARM MID LEVEL
TEMPERATURES WHICH MAY CAP THE ATMOSPHERE.

MBS

&&

.AVIATION...

18Z TAF CYCLE.

DUE TO PLENTY OF LOW LEVEL MOISTURE WITH RECENT RAINS...CYCLONIC
FLOW AT BOTH THE SURFACE AND ALOFT WILL KEEP MVFR CLOUDS AROUND
THROUGH THE DAYLIGHT HOURS. HAVE INCLUDED A TEMPO GROUP UNTIL 20Z
FOR MEM AND JBR WITH THE EXPECTATION THAT ENOUGH MIXING WILL RAISE
CEILINGS AFTER THAT TIME. SOME WEAK GUSTS TO NEAR 20KTS POSSIBLE
AS MIXING SHOULD INCREASING THIS AFTERNOON FOR MKL...MEM...AND
JBR. SOME SHOWER OR THUNDERSTORM CHANCE THIS AFTERNOON AS WEAK
500MB TROF ROTATES THROUGH THE AREA. THIS WAS MENTIONED IN THE
PREVIOUS UPDATED AFD DISCUSSION AT 17Z...HOWEVER WILL NOT MENTION
AT 18Z ISSUANCE DUE TO EXPECTED ISOLATED OR SCATTERED COVERAGE.

HIGH PRESSURE AND DIMINISHING WINDS ARE EXPECTED FOR TONIGHT.
THOUGHT ABOUT FOG FOR TAFS...ESPECIALLY MKL...HOWEVER FOR NOW WITH
LOWERING SURFACE DEW POINTS AND WINDS EXPECTED AROUND THE 5KT RANGE
HAVE LEFT OUT FOR NOW.

BELLES

&&

.PRELIMINARY POINT TEMPS/POPS...
MEM  58  76  57  78 /  20   0  10  20
MKL  53  74  50  76 /  20   0   0  10
JBR  54  75  54  74 /  20   0  10  40
TUP  59  77  54  82 /  20   0   0  10

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
MO...NONE.
MS...NONE.
TN...NONE.
&&

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PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE MEMPHIS TN
451 PM CDT MON MAY 17 2010

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0417 PM     HAIL             FISHER                  35.49N 90.97W
05/17/2010  E0.75 INCH       POINSETT           AR   PUBLIC

0440 PM     HAIL             YORKVILLE               36.10N 89.12W
05/17/2010  E0.88 INCH       GIBSON             TN   EMERGENCY MNGR

            NICKEL SIZE HAIL COVERING THE GROUND

&&

PWB

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