Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 272020
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
320 PM CDT SAT SEP 27 2014

.TONIGHT AND SUNDAY...FORECAST CONFIDENCE - HIGH.

MORE QUIET WEATHER TO FINISH OFF THE WEEKEND. 500 MILLIBAR
CIRCULATION CENTER PROGGD TO PLOD AROUND NW IA OVERNIGHT BEFORE
OPENING UP BEFORE WEAKENING INTO A POSITIVE TILT WEAK OPEN WAVE AND
SLIDING SOUTHEAST ON SUNDAY. MAIN FOCUS ONCE AGAIN WILL BE FOG
TRENDS LATER TONIGHT INTO EARLY SUNDAY MORNING. AIRMASS NOT CHANGING
MUCH AND GRADIENT IS STILL WEAK UNDER THE INFLUENCE OF HIGH
PRESSURE. SREF VSBY PROBS SHOWING BETTER CHANCES IN NRN AND WRN WI.
FOR NOW WILL GO WITH PATCHY FOG DEVELOPMENT. 925 TEMPS SHOW LITTLE
CHANGE FOR SUNDAY SO PERSISTENCE SEEMS PRUDENT ON THE TEMP FRONT.

.SUNDAY NIGHT THROUGH TUESDAY...FORECAST CONFIDENCE - MEDIUM.

WEAKENING UPPER LOW CIRCULATION WILL CONTINUE TO SLIDE SOUTHEAST OF
THE AREA SUN NGT IN RESPONSE TO APPROACHING STRENGTHENING SHORT WAVE
TROF IN SRN CAN.  MORE PATCHY FOG LIKELY SUN NGT AS LITTLE CHANGE IN
AIR MASS AND WINDS REMAIN FAIRLY LIGHT THROUGH A DEEP LAYER.

SHORT TERM GUIDANCE IN POOR AGREEMENT ON STRENGTHEN AND TIMING OF
APPROACHING CAN SHORT WAVE AS IT PASSES ACROSS THE WESTERN GTLAKES
MON/MON EVE. ECMWF MOST AGGRESSIVE WITH TIGHT...COMPACT CIRCULATION
PASSING ACROSS NORTHEAST WI/UP WITH MODERATE PVA CLIPPING EASTERN
CWA IN THE AFTN.  MEANWHILE...GFS AND NAM MUCH WEAKER AND FARTHER
NORTHEAST WITH THIS WAVE.  ECMWF APPEARS TO BE OVERDOING LOW LEVEL
RH ADVECTION FROM THE SOUTH.  HOWEVER ADDITIONAL LIFT FROM MODERATE
FRONTOGENETICAL FORCING VCNTY OF SOUTHWARD SURGING BACKDOOR CDFNT
AND LAYER Q-VECTOR CONVERGENCE TO CONTINUE CHANCE POPS IN NORTHEAST
CWA MON AFTN...ENDING RAPIDLY DURING THE EVE.

SHORT WAVE RIDGING RESULTS IN A QUIET DAY FOR TUESDAY.  STRATUS
SHIELD THAT WILL HAVE SURGED ACROSS SRN WI BEHIND BACKDOOR CDFNT MAY
LINGER FOR A TIME INTO TUE.  NOTICEABLY COOLER TEMPS EXPECTED ON TUE
WITH HIGH TEMPS REMAINING BELOW NORMAL.

.TUESDAY NIGHT THROUGH SATURDAY...FORECAST CONFIDENCE - MEDIUM.

MEDIUM RANGE GUIDANCE IN BETTER AGREEMENT ON TIMING OF MORE
UNSETTLED AND COOLER WEATHER RETURNING TO SOUTHERN WISCONSIN DURING
THIS PERIOD.  INITIALLY...OPEN MID-LEVEL SHORT WAVE TRANSITIONING TO
CLOSED LOW OVER FAR ERN CONUS/FAR WRN ATLANTIC WILL SLOW EWD
PROGRESSION OF LONG WAVE TROFING OVER WESTERN CONUS.  HENCE STRONGER
RETURN FLOW POSTPONED UNTIL WED NGT AND THU.  CONTINUE TO TRIM BACK
POPS FOR WED AFTN IN THE WEST.  BETTER CHANCE FOR PRECIPITATION WED
NIGHT IN INITIAL SURGE OF WARMER...MORE HUMID AIR. HOWEVER A LOT OF
DISAGREEMENT IN EXTENDED GUIDANCE CONCERNING PLACEMENT AND STRENGTH
OF LOW LEVEL JET.  ALSO NOT SEEING MUCH ELEVATED INSTABILITY.
STRENGTHENING LOW PRESSURE MOVING NNE THROUGH SRN CANADA WILL DRAG
SFC CDFNT EWD ACROSS WI THU/THU NGT.  COOLING MID-LEVELS AND PIECES
OF SHORT WAVE ENERGY ROTATING AROUND AMPLIFYING LONG WAVE TROUGH
SHOULD RESULT IN BEST CHANCE FOR PRECIP INCLUDING T DURING THIS PD
AS SYNOPTIC FORCING ELEMENTS COME TOGETHER.  WL CONTINUE LIKELY
WORDING INTO THU NGT.

LONG WAVE TROUGH CONTINUES TO DEEPEN AS IT MOVES ACROSS THE UPPER
MIDWEST/WRN GTLAKES THU NGT/FRI.  THIS WILL ALLOW COLDER AIR TO
OVERSPREAD THE AREA AS 85H TEMPS FALL 10C ON FRI.  A SECOND SURGE OF
COLDER AIR SPREADS IN EARLY IN THE WEEKEND.  DEPENDING ON CLOUD
COVER AND BOUNDARY LAYER MIXING...SAT NIGHT MAY RESULT IN FIRST
PERIOD OF MORE WIDESPREAD FROST ACROSS THE AREA. 00Z ECMWF WAS
OUTLIER WITH REGARD TO AMPLIFICATION OF SHORT WAVE TROUGH TO THE
SOUTH AND SOUTHEAST OF WI OVER THE WEEKEND ALONG BAROCLINIC ZONE.
WL NEED TO WATCH IF THIS TREND CONTINUES AS WOULD HAVE LARGE BEARING
ON FROST POTENTIAL SAT NGT.  GET READY FOR MORE TYPICAL AUTUMN
WEATHER SETTLING IN NEXT WEEKEND.

&&

.AVIATION/00Z TAFS/...

500 MILLIBAR CIRCULATION CENTERED IN NW IA STILL WEAKEN AND SLIDE
SOUTHEAST ON SUNDAY. HIGH LEVEL MOISTURE IN THE FORM OF CIRRUS
WRAPPING NNW INTO SRN WI. SURFACE HIGH WILL CONTINUE TO DOMINATE
INTO SUNDAY WITH A DRY AND STABLE AIRMASS. POTENTIAL FOR MORE PATCHY
FOG DEVELOPMENT LATER TONIGHT AND EARLY SUNDAY. SREF VIS PROBS ARE
SHOWING BETTER POTENTIAL ACRS NRN AND WRN WI WHILE THE MAV/MET MOS
VSBY PROGS ARE AT ODDS. WOULD NOT EXPECT THE SITUATION TO BE MUCH
DIFFERENT THAN LAST NIGHT DUE TO OVERALL STAGNANT PATTERN/LITTLE
AIRMASS MODIFICATION.


&&

.MKX WATCHES/WARNINGS/ADVISORIES...

WI...NONE.
LM...NONE.

&&

$$
TONIGHT/SUNDAY/AVIATION...PC
SUNDAY NIGHT THROUGH SATURDAY..MBK


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