205
FXUS63 KARX 250448
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1148 PM CDT FRI MAY 24 2013
UPDATE
ISSUED AT 646 PM CDT FRI MAY 24 2013
QUICK UPDATE TO REFLECT THE FASTER TIMING OF PRECIPITATION
CURRENTLY ACROSS WESTERN/CENTRAL MINNESOTA. THIS ACTIVITY IS
RIDING ALONG MID LEVEL FRONTOGENESIS AND WARM AIR
ADVECTION...AND COMBINED WITH SOME DECENT UPPER LEVEL FORCING / PV
ADVECTION. MOST OF THE MESO-MODELS AND 18Z GUIDANCE SHOWS THIS
SLIDING SOUTH/EAST MAINLY ALONG AND WEST OF THE MISSISSIPPI RIVER
THROUGH THE OVERNIGHT. SO HAVE SPED UP PRECIPITATION WORDING TO
ACCOUNT FOR THIS. OTHERWISE...FORECAST REMAINS ON TRACK.
SHORT TERM
(THIS EVENING THROUGH SATURDAY)
ISSUED AT 334 PM CDT FRI MAY 24 2013
AT 3 PM...A 1003 MB HIGH PRESSURE SYSTEM...CENTERED OVER LAKE
MICHIGAN...KEPT SKIES PARTLY SUNNY ACROSS THE UPPER MISSISSIPPI
RIVER VALLEY. MEANWHILE FURTHER WEST...A SHORT WAVE WAS PRODUCING
SHOWERS AND THUNDERSTORMS ACROSS THE EASTERN QUARTER OF THE
DAKOTAS AND WESTERN MINNESOTA. THE MESO AND DETERMINISTIC MODELS ARE
CONTINUING TO STRUGGLE WITH THE EASTWARD PROGRESS OF THIS
PRECIPITATION TONIGHT. THE ECMWF AND HRRR MOVE THIS PRECIPITATION
ACROSS MOST OF FORECAST AREA BY 25.06Z. MEANWHILE THE
NMM...ARW...GFS...GEM...RAP... AND NAM MAINLY CONFINE THE
PRECIPITATION WEST OF THE MISSISSIPPI RIVER THIS EVENING...AND
THEN MOVES IT ACROSS THE REMAINDER OF THE AREA OVERNIGHT. SINCE
THE CONVECTION ACROSS THE DAKOTAS WILL BE MOVING INTO AN AREA WITH
LESS FRONTOGENETIC FORCING...MOISTURE TRANSPORT...WEAK ISENTROPIC
LIFT...AND DRIER AIR...DECIDED TO TREND THE FORECAST TOWARD THE
LATTER MODEL SET. IN ADDITION...THE RADAR ECHOS ACROSS WESTERN
MINNESOTA ARE SHOWING A DECREASING TREND. EVEN BY DOING
THIS...THERE IS SOME VARIATIONS AMONGST THEM...SO TRIED TO GO WITH
AN ENSEMBLE APPROACH WHEN ASSIGNING THE HOURLY PRECIPITATION
CHANCES. THE HIGHEST PRECIPITATION CHANCE AND AMOUNTS /UP TO A
HALF INCH/ WILL BE FOUND ACROSS ACROSS SOUTHEAST MINNESOTA AND
NORTHEAST IOWA.
ON SATURDAY...THE SHORT WAVE WILL MOVE EAST SOUTHEAST ACROSS IOWA.
AS THIS OCCURS...THE 850 MB MOISTURE TRANSPORT AND ISENTROPIC LIFT
WILL GRADUALLY WEAKEN. AS A RESULT...WENT WITH A DECREASING TREND
IN THE PRECIPITATION TRENDS FROM LATE MORNING INTO THE AFTERNOON.
ADDITIONAL RAINFALL AMOUNTS WILL BE LESS THAN 2 TENTHS OF AN INCH.
WITH THE 24.12Z AND 24.18Z MODELS IN GOOD AGREEMENT THAT THERE
WILL BE LESS THAN 100 J/KG CAPES...JUST KEPT AN ISOLATED
THUNDERSTORM CHANCE MAINLY WEST AND SOUTH IF THE INTERSTATE 94
CORRIDOR.
LONG TERM
(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 334 PM CDT FRI MAY 24 2013
FROM SATURDAY NIGHT THROUGH SUNDAY NIGHT...THE WARM FRONT WILL
REMAIN WELL SOUTHWEST OF THE FORECAST AREA. AS A RESULT...
SOUTHEAST MINNESOTA...NORTHEAST IOWA...AND SOUTHWEST WISCONSIN
WILL REMAIN CLOUDY WITH PERIODIC SHOWERS AND MAYBE AN ISOLATED
THUNDERSTORM. OVER THE PAST 3 DAYS...THE CONSALL HAS CONTINUED
TO TREND TOWARD COOLER HIGH TEMPERATURES FOR SUNDAY. IT NOW HAS
HIGH TEMPERATURES AROUND 60. MEANWHILE THE ECMWF ONLY HAS HIGH
TEMPERATURES IN THE LOWER 50S FOR THESE AREAS. SINCE THE ECMWF
TYPICALLY VERIFIES THE BEST FOR THIS TIME PERIOD...WENT WITH A
BLEND OF THE CONSALL...CONSALLBC...AND ECMWF.
FROM MEMORIAL DAY INTO TUESDAY...THE MODELS ARE CONTINUING TO SHOW
THAT A WARM FRONT WILL MOVE NORTHWARD INTO THE AREA. THIS WILL
ALLOW ML CAPES TO CLIMB INTO THE 1K TO 3K J/KG RANGE. AS A
RESULT...EXPECT THE THUNDERSTORM CHANCES TO INCREASE DURING THIS
TIME PERIOD. THE 0-3KM SHEAR WOULD BE FAVORABLE FOR THE
POSSIBILITY THAT A FEW THUNDERSTORMS MAY BE CAPABLE OF PRODUCING
LARGE HAIL AND DAMAGING WINDS.
FROM TUESDAY NIGHT INTO FRIDAY...THE MODELS CONTINUE TO STRUGGLE
ON WHERE THE WARM SECTOR WILL BE LOCATED. THIS GREATLY AFFECTS
THE WHERE THE PRECIPITATION MAY BE LOCATED. IN ADDITION...IT WILL
ALSO AFFECT THE SHEAR AND INSTABILITY...THUS...THERE IS A LOT OF
UNCERTAINTY ON WHETHER THERE WILL BE ANY SEVERE WEATHER.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1148 PM CDT FRI MAY 24 2013
A BAND OF LIGHT TO MODERATE RAIN HAS SET UP ALONG AND JUST TO THE
WEST OF THE MISSISSIPPI RIVER AND IS EXPECTED TO PERSIST THROUGH
THE OVERNIGHT HOURS. AS THE FORCING WEAKENS LATER THIS
MORNING...EXPECT THAT THE RAIN WILL COME TO AN END THOUGH SOME
MVFR CEILINGS WILL BECOME POSSIBLE AT RST. CURRENT THINKING IS
THAT CONDITIONS SHOULD MAINLY BE DRY THROUGH THE REST OF THE DAY
WITH OVERALL FORCING BEING WEAK INTO THE NIGHT. THE MAIN QUESTION
WILL BE WHETHER THERE WILL BE ENOUGH LOW LEVEL MOISTURE TRAPPED
UNDER THE SHALLOW INVERSION AROUND 3KFT TO PRODUCE SOME MVFR
CEILINGS...PARTICULARLY AT RST. WITH CONFIDENCE NOT AS HIGH AS IT
PREVIOUSLY WAS...HAVE REMOVED IT FROM THE FORECAST.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
UPDATE...ZT
SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...HALBACH
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