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000
FXUS63 KARX 202026
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
325 PM CDT MON MAY 20 2013

.SHORT TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 325 PM CDT MON MAY 20 2013

SURFACE MAP THIS AFTERNOON HAS A DEEP 995MB LOW OVER NORTHEAST SD
WITH A COLD FRONT/OCCLUSION EXTENDING SOUTHEAST OUT OF THE LOW INTO CENTRAL
MN/WI. DEW POINT ANALYSIS SHOWS DRIER AIR HAS PUSHED INTO THE AREA
TODAY BEHIND THE COLD FRONT. VIS SATELLITE SHOWING GROWING CUMULUS
FIELD GROWING ACROSS THE AREA...WITH LAPS INDICATING 0-1KM MLCAPE
ONLY AROUND 500J/KG AT THIS TIME. MEANWHILE...WATER VAPOR
IMAGERY/RAP H3 ANALYSIS SHOWING A JET MAX LIFTING NORTHEAST OUT OF
KS TOWARD THE AREA. THIS FEATURE IS EXPECTED TO INTERACT WITH A
DRYLINE MOVING NORTHEAST OUT OF NEB THIS EVENING FOR ANOTHER ROUND
OF SHOWERS AND THUNDERSTORMS. RAP13 SHOWS 0-1KM CAPE INCREASING INTO
THE 1300J/KG BY 03Z ALONG WITH AMPLE 0-3KM BULK SHEAR IN THE 35-40KT
RANGE. APPEAR STAGE IS SET FOR ANOTHER SEVERE THREAT WITH DAMAGING
WIND AND LARGE HAIL BEING THE MAIN THREAT. TORNADO THREAT APPEARS
SLIGHTLY DIMINISHED AT THIS POINT DUE TO HIGHER LIFTED CONDENSATION
LEVELS/LCLS.  LOOKING FOR THE CONVECTION TO WANE AFTER MIDNIGHT AS
THE BOUNDARY AND MOISTURE TRANSPORT MOVES NORTHEAST OUT OF THE AREA.

FOR TUESDAY...EXPECTING SLIGHTLY DRIER AIR TO OVERSPREAD MUCH OF THE
AREA IN DRY SLOT OF THE LOW AS IT MOVES THROUGH SOUTHERN MN. FAIRLY
STEEP LAPSE RATES WILL BE IN PLACE...HOWEVER WITH NO DEFINITE
BOUNDARY TO FOCUS CONVECTION...WENT WITH LOWER-END CONVECTION
PROBABILITIES SOUTHWEST OF I-94 WITH HIGHER POPS NORTHEAST OF THIS.
OTHERWISE...PLAN ON COOLER BUT NEAR NORMAL HIGH TEMPERATURES IN THE
70S.

.LONG TERM...(TUESDAY NIGHT THROUGH MEMORIAL DAY)
ISSUED AT 325 PM CDT MON MAY 20 2013

A BREAK IN THE ACTION IS EXPECTED TUESDAY NIGHT AS THE DRY SLOT OF
THE LOW CONTINUES TO WORK NORTHEAST THROUGH THE AREA AND DEFORMATION
SHRA/TS ACTIVITY REMAINS NORTHWEST. FOR WEDNESDAY...LOOK FOR THE LOW
TO SLIP EAST TOWARD SOUTHERN LAKE MICHIGAN WITH THE DEFORMATION
SHRA/ISOLATED THUNDER WORKING SOUTHEAST ACROSS THE AREA. WITH THE
DYNAMIC COOLING OF THE UPPER LOW/CLOUDS/PRECIPITATION...PLAN ON
HIGHS ONLY IN THE 60S. SHOWER CHANCES STAY IN THE FORECAST THROUGH
WEDNESDAY NIGHT/THURSDAY MORNING AS THE LOW SLOWLY MOVES EAST INTO
THE GREAT LAKES REGION.

FOR THURSDAY NIGHT/FRIDAY...APPEARS MUCH DRIER AIR WILL ADVECT INTO
THE AREA ON NORTH/NORTHEAST WINDS FROM HIGH PRESSURE OVER ONTARIO
CANADA. HIGHS COOL TREND CONTINUES THURSDAY/FRIDAY WITH READINGS
TOPPING OFF IN THE 60S.

SHOWER AND THUNDERSTORMS EXPECTED TO RE-ENTER THE PICTURE FRIDAY
NIGHT AND THEN LAST INTO SATURDAY AS A MID-LEVEL TROUGH OF LOW
PRESSURE MOVES THROUGH THE NORTHERN PLAINS INTO IA. APPEARS HIGHEST
PROBABILITY RAIN CHANCES REMAIN SOUTHWEST OF I-94 WITH DRIER
SOUTHEAST OUTFLOW OUT OF HIGH PRESSURE DROPPING INTO THE GREAT LAKES
REGION. RAIN CHANCES GET A LITTLE IFFY THROUGH THE REMAINDER OF THE
WEEKEND WITH THAT WEAK MID-LEVEL WAVE SKIMMING SOUTH OF THE AREA AND
HIGH PRESSURE REMAINING OVER ONTARIO/GREAT LAKES REGION. ONE THING
LOOKS SURE THOUGH...AND THAT COOLER THAN NORMAL TEMPERATURES WITH
HIGHS SATURDAY AND SUNDAY REMAINING IN THE 60S...WARMING SLIGHTLY
INTO THE MID 60S/LOWER 70S FOR MEMORIAL DAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON) ISSUED
AT 1235 PM CDT MON MAY 20 2013

AS UPPER LOW GETS CLOSER TO THE AREA...SOME STRATUS AND CUMULUS
FIELD WRAPPING BACK INTO THE AREA FROM BRIEF CLEARING...BUT MOST
CEILINGS VFR. WATCHING FOR ADDITIONAL CONVECTION THIS AFTERNOON BUT
STORM OCCLUSION AND SLIGHTLY DRIER AIR IN THE FORM OF LOWER CAPE
VALUES MAY KEEP STORMS SLIGHTLY WEAKER THAN YESTERDAY...IN ADDITION
TO A BIT MORE SOUTH AND EAST. WILL KEEP STORMS IN A VICINITY MODE
UNTIL MORE DETAIL CAN BE WORKED IN BUT THREAT SHOULD END BY
OVERNIGHT HOURS AS ANY CAPE DIMINISHES.

GENERALLY A VFR CEILING EXPECTED AS UPPER LOW SPINS AROUND THE AREA
FOR ANOTHER DAY OR TWO BUT SOME MVFR TIME IS POSSIBLE WITH LOWER
STRATUS FIELDS OR ROUNDS OF SHOWERS.

&&

.HYDROLOGY...
ISSUED AT 325 PM CDT MON MAY 20 2013

WITH BETTER FOCUS FOR CONVECTION THIS EVENING BEING ALONG AND EAST
OF THE MISSISSIPPI RIVER....HAVE DECIDED TO DROP THE FLOOD WATCH
THAT WAS IN EFFECT FOR PORTIONS OF SOUTHEAST MN/A PART OF NORTHEAST
IA. HOWEVER...WILL HAVE TO REMAIN ON HIGH ALERT FOR RIVER
FLOODING...PARTICULARLY ALONG THE ROOT RIVER IN SOUTHEAST MN AND THE
CEDAR IN NORTHEAST WHERE RIVER FLOOD WARNINGS ARE IN EFFECT. OTHER
RIVERS AND TRIBUTARIES WILL ALSO HAVE TO WATCHED ACROSS SOUTHEAST
MN/NORTHEAST IA FOR RISING WITHIN BANK LEVELS FROM RECENT HEAVY
RAINFALL ACTIVITY. DRYING EXPECTED FINALLY ON THURSDAY AS HIGH
PRESSURE NOSES IN FROM CANADA.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...DAS
LONG TERM...DAS
AVIATION...SHEA
HYDROLOGY...DAS