Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 240844
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
344 AM CDT SUN AUG 24 2014

.TODAY AND TONIGHT...FORECAST CONFIDENCE IS HIGH.

THE MID/UPPER LEVEL RIDGE FROM THE SOUTHEAST U.S. TO THE LAKE
MICHIGAN AREA WILL PUSH OFF INTO LOWER MICHIGAN BY NOON AS THE
SOUTHWEST UPPER JET LIFTS NORTH ACROSS THE DAKOTA/MINNESOTA BORDER
WITH LIGHT SOUTHWEST FLOW ACROSS SOUTHERN WISCONSIN. NOT MUCH IN
THE WAY OF UPPER DIVERGENCE OR 700 MB UPWARD MOTION UNTIL SOME
WEAK UPPER DIVERGENCE AND UPWARD MOTION AFFECTS SOUTHERN WISCONSIN
LATE TONIGHT.

THE 700 MB WIND FLOW IS VERY WEAK THIS MORNING AND BECOMES WEST
THEN SOUTHWEST LATE TONIGHT...INCREASING TO AROUND 20 KNOTS MAINLY
TOWARDS THE DELLS LATE TONIGHT. THE 850 MB FLOW IS A LITTLE
STRONGER INTO FAR WESTERN WISCONSIN BY EVENING...BUT REMAINS
RATHER WEAK ACROSS SOUTHERN WISCONSIN. 850 MB TEMPERATURES RISE TO
AROUND 21 CELSIUS THIS AFTERNOON AND TONIGHT.

NAM ZERO TO 1 KM MIXED LAYER CAPE RISES TO AROUND 3400 JOULES/KG
OVER WESTERN PORTIONS OF SOUTH EAST WISCONSIN AND 4600 JOULES/KG
TOWARDS THE DELLS. A RATHER STRONG CAP EXISTS OVER SOUTHEAST
WISCONSIN...BUT THE NAM DOES WEAKEN IT IN THE FAR NORTHWEST
SECTIONS BY THE DELLS WHERE THE LOW LEVELS BECOME FAIRLY WELL
MIXED. THUS WE HAVE THE MOISTURE AND INSTABILITY...BUT WE LACK A
GOOD LIFTING MECHANISM.

A SOUTHEAST FLOW OFF LAKE MICHIGAN MAY KEEP AREAS NEAR LAKE
MICHIGAN IN STRATUS...ESPECIALLY NORTH OF MILWAUKEE WITH MUCH
COOLER TEMPERATURES THAN INLAND AREAS. IN AREAS WEST OF MADISON
HEAT INDEX VALUES MAY APPROACH HEAT ADVISORY LEVELS...BUT SHOULD
REMAIN BELOW 100 OVER MOST AREAS.

THE MODELS BRING MOIST CONVECTION CLOSE TO THE FORECAST AREA
LATER TONIGHT...BUT THE NAM AND 4 KM WRF KEEP OUR FORECAST AREA
DRY. WILL HAVE A CHANCE WORDING FOR THUNDERSTORM POTENTIAL LATER
TONIGHT ESPECIALLY NORTHWEST AND NORTH OF MADISON.

.SHORT TERM...MONDAY THROUGH TUESDAY NIGHT...FORECAST CONFIDENCE
IS MEDIUM.

MODELS BRING COLD FRONT SOUTHEASTWARD TOWARD THE AREA
MONDAY...THEN ACROSS THE AREA MONDAY NIGHT INTO TUESDAY...SAGGING
SOUTH OF THE AREA TUESDAY NIGHT. NAM/ECMWF/CANADIAN MODELS ALL
SHOWING THIS TREND. THE GFS SHOWS LOW PRESSURE SHIFTING NORTHEAST
INTO IOWA TUESDAY NIGHT...WHICH BRINGS FRONT BACK NORTH AS A WARM
FRONT. THIS IS AN OUTLIER SOLUTION. MODEST 850 MB LOW LEVEL JET
AXIS SHIFTS ACROSS THE AREA MONDAY...THEN WEAKENS MONDAY NIGHT
INTO TUESDAY. MODELS ALSO BRING 500 MB VORTICITY MAXIMUM THROUGH
THE AREA TUESDAY.

KEPT HIGHER END CHANCE TO LOW END LIKELY POPS FOR THIS
PERIOD...WITH BEST CHANCES IN THE FAR WEST MONDAY NIGHT WITH
FRONTAL APPROACH AND TUESDAY NIGHT ACROSS MOST OF THE AREA WITH
ELEVATED CONVECTION FORMING NEAR 850 MB CONFLUENCE/CONVERGENCE.

AREA FORECAST SOUNDINGS FROM NAM SHOWING HIGH MEAN LAYER AND
ELEVATED CAPES GREATER THAN 3000 J/KG MONDAY...TO 1000 TO 2000
J/KG MONDAY NIGHT INTO TUESDAY...LOWERING MORE TUESDAY NIGHT.
DEEP LAYER SHEAR IS MODEST AROUND 20 KNOTS MONDAY...THEN IS
SOMEWHAT STRONGER AROUND 30 KNOTS ON TUESDAY.

PRECIPITABLE WATER VALUES REMAIN IN THE 1.70 TO 1.80 INCH RANGE
DURING THE MONDAY THROUGH TUESDAY NIGHT PERIOD. CWASP VALUES FROM
NAM MODEST DURING THIS PERIOD. ISOLATED LARGE HAIL AND GUSTY
WINDS ARE POSSIBLE FROM ANY STORMS...AS WELL AS HEAVY RAINFALL
PRODUCING SOME LOCALIZED FLOODING.

HEAT INDEX VALUES MONDAY WILL REACH THE 95 TO 99 DEGREE RANGE
ACROSS A GOOD PORTION OF THE AREA...AND WILL HAVE TO BE WATCHED
FOR A POSSIBLE HEAT ADVISORY IN LATER FORECASTS. WARM AND HUMID
CONDITIONS WILL CONTINUE THROUGH THIS PERIOD.

.LONG TERM...WEDNESDAY THROUGH SATURDAY...FORECAST CONFIDENCE IS
MEDIUM.

GFS AND ECMWF DIFFER QUITE A BIT WITH TIMING AND PLACEMENT OF
FEATURES DURING THIS PERIOD. SECONDARY SURFACE LOW ON GFS HELPS TO
SLOW DOWN SYSTEM AND LINGERS PRECIPITATION WEDNESDAY INTO
THURSDAY ACROSS THE AREA. MAIN 500 MB SHORTWAVE TROUGH MOVES
THROUGH THE AREA DURING THIS TIME. HIGH PRESSURE THEN BRINGS QUIET
WEATHER FOR FRIDAY INTO SATURDAY.

ECMWF BRINGS HIGH PRESSURE INFLUENCE INTO THE AREA WEDNESDAY INTO
THURSDAY...BEFORE NEXT SYSTEM FROM THE WEST MOVES INTO THE REGION
FOR THURSDAY NIGHT INTO FRIDAY. FOR NOW...WILL USE CONSENSUS BLEND
OF MODEL POPS FOR THIS PERIOD UNTIL BETTER AGREEMENT AMONG THE
MODELS CAN BE REACHED. COOLER AND LESS HUMID CONDITIONS ARE
POSSIBLE ONCE MAIN COLD FRONT MOVES THROUGH THE REGION.

&&

.AVIATION/12Z TAFS/...

AREAS OF IFR CIGS AND MVFR VSBYS THIS MORNING...WITH PATCHY LIFR
CIGS/IFR VSBYS. MOIST LOW LEVELS WITH A LIGHT SOUTH FLOW. THEN
EXPECT MAINLY VFR CONDITIONS WITH SCATTERED CUMULUS BY AFTERNOON
FOR MUCH OF THE AREA. HOWEVER A SOUTHEAST FLOW OFF LAKE MICHIGAN
MAY KEEP AREAS NEAR LAKE MICHIGAN IN IFR STRATUS/MVFR
FOG...ESPECIALLY NORTH OF MILWAUKEE.

&&

.MARINE...

A VERY MOIST AIR MASS AND LIGHT SOUTHEAST WINDS OVER THE
RELATIVELY COOLER WATERS OF LAKE MICHIGAN HAS LED TO CONTINUED FOG
OVER THE SOUTHEAST WISCONSIN NEARSHORE WATERS OF LAKE MICHIGAN.
AREAS NORTH OF MILWAUKEE WOULD BE MOST LIKELY TO EXPERIENCE DENSE
FOG.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

$$

TODAY/TONIGHT AND AVIATION/MARINE...HENTZ
MONDAY THROUGH SATURDAY...WOOD



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