Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 270239
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
939 PM CDT FRI SEP 26 2014

.UPDATE...

PATCHY FOG IS DROPPING VSBYS AT KSBM...KRAC AND KENW...THOUGH WEB
CAMS SHOW IT IS NOT YET WIDESPREAD. CURRENT FORECAST HAS POTENTIAL
AREAS OF FOG WELL OUTLINED PER SREF VSBY PROBABILITY FORECAST AND
LATEST NAM VSBY PROG...AFFECTING THE LAKE SHORE COUNTIES AND
ADJACENT PORTIONS OF THE NEXT TIER OF COUNTIES TO THE WEST.

WILL KEEP AN EYE ON OBS AND SATELLITE FOG PRODUCT FOR ANY CHANGES
BUT PLAN TO HOLD ON TO CURRENT FORECAST...WITH SOME MINOR
TEMPS/DEW POINT TWEAKS.

&&

.AVIATION/06Z TAFS/...

PATCHY FOG BEGINNING TO DEVELOP IN THE EASTERN FORECAST AREA NEAR
LAKE MICHIGAN...WITH VSBYS DROPPING AT KSBM...KRAC AND KENW IN
GROUND FOG...WITH OTHER OBS AND WEB CAMS SHOWING FOG IS NOT
WIDESPREAD. EXPECT IFR CONDITIONS OVERNIGHT AT KENW...AND AT KMSN
FOR A FEW HOURS AROUND DAWN. OTHER TAF SITES EXPECTED TO GO NO
LOWER THAN MVFR. MOST FOG DISSIPATES BY 13Z-14Z SATURDAY...BUT MAY
BE SLOWER TO CLEAR NEAR THE LAKE. VFR CONDITIONS THROUGH THE
REMAINDER OF THE FORECAST...THOUGH AREAS OF FOG EXPECTED IN THE
EAST AGAIN LATE SATURDAY NIGHT WITH PATCHY FOG ELSEWHERE.

&&

.PREV DISCUSSION... /ISSUED 328 PM CDT FRI SEP 26 2014/

TONIGHT - CONFIDENCE...MEDIUM

SURFACE HIGH CONTINUES TO DOMINATE. BROAD 500 MILLIBAR CIRCULATION
ACRS NRN MO/SRN IA PROGGD TO RETROGRADE A BIT TO THE NORTHWEST. MAIN
CONCERN WILL BE FOG DEVELOPMENT. NOT MUCH CHANGE FROM LAST NIGHT
OTHER THAN SLIGHTLY HIGHER DEWPOINTS. ALSO NOTICING AN INCREASE IN
SE WINDS WITHIN A FEW OF THE LOWER GATES ON RAP SOUNDINGS. FOG WILL
BE QUITE SHALLOW AS COLUMN IS MOISTURE STARVED. NAM MOS A LITTLE
MORE ROBUST THAN THE GFS MOS BUT THIS IS TYPICAL. SREF PROBS NOT TOO
EXCITED BUT OVERALL PERSISTENCE SEEMS PRUDENT GIVEN THE OVERALL
STAGNANT PATTERN. WILL NOT HOIST AN ADVISORY AT THIS TIME AS
CONFIDENCE IN WIDESPREAD DENSE NOT HIGH AT THIS TIME...BUT POTENTIAL
THERE FOR AT LEAST PATCHY DENSE FOG.

SATURDAY - CONFIDENCE...HIGH

UPPER LOW PROGGD TO BE AROUND NW IA/SW MN. HIGH PRESSURE RIDGE
DOMINATES WITH THE DRY AND STABLE AIRMASS PERSISTING. MORNING FOG
TRENDS WILL BE THE MAIN FOCUS WITH ANY LINGERING FOG LIKELY TO BURN
OFF IN MUCH THE SAME FASHION AS FRIDAY MORNING. 925 TEMPS AROUND 17-
18C...SO HIGHS WELL INTO THE 70S.

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

MORE FOG POSSIBLE SATURDAY NIGHT AS BOUNDARY LAYER WINDS REMAIN
AROUND 10 KNOTS OR LESS.  SFC DEWPTS CONTINUE TO SLOWLY RISE EACH
DAY DUE TO THE STAGNATING AIR MASS.  HENCE THE LIGHT WINDS AND
MOSTLY CLEAR SKIES SHOULD ALLOW OVERNIGHT TEMPS TO FALL BELOW THE
DAYTIME CROSS OVER TEMP ONCE AGAIN.

OTHERWISE...THE QUIET CONDITIONS WILL CONTINUE THROUGH MONDAY
MORNING.  MOST OF THE SHORT TERM GUIDANCE SHOWING AN AMPLIFYING
SHORT WAVE TROUGH FURTHER STRENGTHENING ALONG BAROCLINIC ZONE DRAPED
ACROSS NORTHERN GTLAKES SUN NGT AND MON.  THIS HIGHER AMPLITUDE WAVE
AND LOW PRESSURE RESULTS IN QUICKER SOUTHWARD MOVEMENT OF BACKDOOR
COLD FRONT ACROSS WESTERN GTLAKES ON MONDAY.  ELEVATED MOISTURE
STILL LIMITED AS FRONT CROSSES REGION SO FOR NOW...WL CONTINUE SCHC
WORDING IN THE NORTHEAST CWA...CLOSER TO UPPER LEVEL CIRCULATION.
LATER PERIODS OF NAM REMAIN OUTLIER WITH ITS SLOWER SWD MOVEMENT.
IF THIS TREND CONTINUES WL NEED TO BUMP UP WINDS AND SPEED UP MORE
ABRUPT WIND CHANGE LATER MONDAY INTO MONDAY EVENING.

MONDAY NIGHT THROUGH FRIDAY...FORECAST CONFIDENCE - MEDIUM TRENDING
TOWARD LOW.

AS MENTIONED ABOVE...MEDIUM RANGE GUIDANCE IN GOOD AGREEMENT ON
AMPLIFYING SHORT WAVE TROUGH OVER WESTERN GTLAKES CONTINUING TO
STRENGTHEN AS IT TRACKS EWD MONDAY AND MONDAY NIGHT.  STRONGER SHORT
WAVE WILL PULL BACKDOOR CDFNT SWD ACROSS SRN WI ABOUT 12 HOURS
EARLIER THAN THOUGHT 24 HOURS AGO.  HENCE CDFNT NOW EXPECTED TO
ADVANCE SOUTH OF SRN WI/LAKE MI BY 00Z/TUE.  WL KEEP A CHANCE FOR -
SHRA IN THE EVE IN PARTS OF EAST BUT DRIER...COOLER AIR WILL END
THREAT OVERNIGHT.  LIKELY SOME LOW CLOUDS/STRATUS WL ACCOMPANY PUSH
OF COLDER AIR POST FRONTAL PASSAGE.

SHORT WAVE RIDGING SHOULD RESULT IN QUIET AND DRY CONDITIONS
RETURNING AT LEAST TEMPORARILY TUE/TUE NGT.

MEANWHILE...BROADENING LONG WAVE TROUGH OVER WRN CONUS WILL RESULT
IN INCREASING SLY WINDS OVER THE WRN GTLAKES AROUND MID WEEK AS
SEVERAL PIECES OF SHORT WAVE ENERGY ROTATE NORTHWARD ACROSS THE
NORTHERN PLAINS/UPPER MIDWEST.  AS A RESULT...COLUMN PRECIPITABLE
WATER INCREASES TO AROUND 1.5 INCHES BY 00Z/THU.  INITIAL SURGE OF
MOISTURE MAY SET OFF PRECIPITATION ON WED...WITH BETTER CHANCE IN
THU/THU NGT TIME FRAME WHEN STRONG CDFNT AND SHARP MID-LEVEL SHORT
WAVE PASS ACROSS THE REGION.  00Z MEDIUM RANGE GUIDANCE RAPIDLY
DIVERGED AFTER THAT AS GFS CONTINUED TO CARVE OUT COLD LONG WAVE
TROUGH OVER THE REGION...WHILE ECMWF RETURNS TO WARMER...MORE ZONAL
FLOW FOR THE WEEKEND.  HOWEVER 12Z ECMWF/GFS FLIP FLOPPED SOMEWHAT
WITH ECMWF NOW SHOWING COLD AIR SURGING INTO SRN WI FOR THE
WEEKEND...WHILE GFS TRENDS TOWARD MORE ZONAL FLOW.  HENCE LOW
CONFIDENCE IN LATE PERIODS

DISAGREEMENT BEGINS UPSTREAM OVER WRN CONUS AND NORTHERN PACIFIC WRT
AMOUNT OF AMPLIFICATION OF NORTHERN PACIFIC TROF AND RIDGING OVER
WRN CONUS.  GFS ENSEMBLE MEMBERS SHOWING LARGE VARIABILITY IN UPPER
LEVEL FEATURES DURING THIS PERIOD...SO WOULD OPT FOR AN AVERAGE OF
ALL GUIDANCE FOR NEXT WEEKEND.

AVIATION/00Z TAFS/...MOSTLY VFR PERIOD WITH SURFACE HIGH HAVING
STRONG INFLUENCE WITH DRY AND STABLE AIRMASS. WATER VAPOR/RAP SHOWS
RATHER BROAD CIRCULATION CENTER VCNTY NW MO/SE IA. WILL WATCH FOR
MORE FOG DEVELOPMENT TONIGHT WITH SOME IFR VSBYS POSSIBLE. ANY FOG
WILL DISSIPATE SATURDAY MORNING AS HEATING KICKS IN.

MARINE...FOG WILL LIKELY DEVELOP ONCE AGAIN OVER EASTERN WI THIS
EVENING AND OVERNIGHT AND SOME OF THIS FOG MAY DEVELOP OVER THE
NEARSHORE WATERS AS WELL.

&&

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

$$

UPDATE...REM
TONIGHT/SATURDAY AND AVIATION/MARINE...COLLAR
SATURDAY NIGHT THROUGH FRIDAY...MBK



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