Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 172049
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
349 PM CDT SUN AUG 17 2014

.TONIGHT AND MONDAY...FORECAST CONFIDENCE IS MEDIUM.

LOW CLOUDS HAVE MIXED OUT IN ALL BUT THE SOUTHWEST THIRD OF THE
FORECAST AREA...MAINLY SOUTHWEST OF MADISON. PEAK HEATING OVER THE
NEXT HOUR OR SO SHOULD HELP THE REMAINING LOW STRATUS BECOME
SCATTERED TO BROKEN. SOME LOW STRATUS OVER LAKE MICHIGAN SHOULD ALSO
BECOME SCATTERED TO BROKEN AROUND AND SOUTH OF MILWAUKEE.

HIGH PRESSURE INFLUENCE TO THE NORTHEAST OF THE AREA SHOULD HELP
WINDS BECOME LIGHT BY LATER THIS EVENING AND INTO EARLY MONDAY
MORNING. DEW POINT DEPRESSIONS SHOULD BECOME SMALL DURING THIS TIME.
NAM/GFS MOS INDICATING LOW STRATUS DEVELOPING ONCE AGAIN...WITH SOME
FOG AS WELL. GIVEN LAST FEW NIGHTS OF LOW STRATUS...THINK THIS IS
REASONABLE. NOT SURE ABOUT DENSE FOG...AS LOW STRATUS MAY KEEP
VISIBILITIES UP ENOUGH. WENT WITH PATCHY/AREAS OF FOG LATER TONIGHT
AND EARLY MONDAY MORNING ACROSS MOST OF THE AREA. LOWS IN THE UPPER
50S TO LOWER 60S ARE EXPECTED.

SURFACE LOW PRESSURE WILL MOVE EAST SOUTHEAST TOWARD NORTHWEST
WISCONSIN LATER TONIGHT AND MONDAY. LEAD 500 MB VORTICITY MAXIMUM
WILL SHIFT EASTWARD INTO WISCONSIN MONDAY...WITHIN BROADER SHORTWAVE
TROUGH. DIVERGENCE FROM RIGHT ENTRANCE REGION OF 250 MB JET STREAK
ALSO MOVES INTO WISCONSIN BY 00Z TUESDAY. SHOULD BE ENOUGH UPWARD
VERTICAL MOTION TO CONTINUE TRENDING UPWARDS TO LIKELY POPS IN THE
FAR WEST LATER MONDAY AFTERNOON...LOWER IN THE EAST.

AREA FORECAST SOUNDINGS FROM NAM/GFS SHOWING UP TO 1000 J/KG OF MEAN
LAYER CAPE...ADJUSTING MODEL DEW POINTS...WITH AROUND 20 KNOTS OR SO
OF DEEP LAYER SHEAR. PRECIPITABLE WATER VALUES ARE AROUND 1.80
INCHES BY LATE MONDAY...WITH SLOW PROPAGATION VECTORS. THUS...SLOWER
MOVING STORMS MAY PRODUCE BRIEF HEAVY RAINFALL...ALONG WITH SMALL
HAIL AND BRIEF GUSTY WINDS.

.SHORT TERM...MONDAY NIGHT THROUGH WEDNESDAY NIGHT.

MONDAY NIGHT...FORECAST CONFIDENCE HIGH

THUNDERSTORMS WILL BE ONGOING IN THE WEST AT THE START OF THE
PERIOD...SPREADING EAST IN THE EVENING AND LASTING THROUGH THE
OVERNIGHT WITH FORCING FROM A SERIES OF VORTICITY MAXIMA ROTATING
AROUND DEEPENING 500 MB TROUGH.

SOME 0-6KM SHEAR...GENERALLY ON THE ORDER OF 20 TO 25 KNOTS...BUT
MODEST MID-LEVEL LAPSE RATES THAT REMAIN LESS THAN 7C/KM WILL LIMIT
CAPE AND POTENTIAL FOR ROBUST UPDRAFTS FOR WIDESPREAD SEVERE. STORMS
COULD GENERATE HEAVY DOWNPOURS WITH PWS IN THE 1.5 TO 1.7 INCH RANGE
BUT MESO-BETA ELEMENT VELOCITIES ARE 10-15 KNOTS...AND WITH
GENERALLY DRY CONDITIONS AND FLASH FLOOD GUIDANCE ON THE ORDER OF
1.9 TO 2 INCHES FOR ONE HOUR...NO PLANS FOR AN ESF OR WATCH.

TUESDAY AND TUESDAY NIGHT...FORECAST CONFIDENCE MEDIUM.

SHOWERS AND STORMS WILL BEGIN TO SLOWLY TAPER OFF FROM WEST TO EAST
AS TROUGH AND ATTENDANT SURFACE LOW SHIFT EAST...BUT SLOW MOVEMENT
OF CLOSED 500 MB FEATURE IN WEAK FLOW WILL KEEP LIKELY POPS IN THE
EAST AND MID-HIGH CHANCE POPS IN THE WEST THROUGH TUESDAY AFTERNOON.
DRY AIR AND SUBSIDENCE WITH WEAK SHORT WAVE RIDGING TO PUSH PCPN TO
THE EAST BY 12Z WED.

WEDNESDAY AND WEDNESDAY NIGHT...FORECAST CONFIDENCE LOW.

MODELS GENERALLY AGREE THAT WEDNESDAY WILL BE DRY...THOUGH KEPT A
COLLABORATIVE SLIGHT CHANCE IN THE FAR SOUTH IN THE MORNING AND CWA-
WIDE IN THE AFTERNOON DUE TO DIFFERENCES WITH LOCATION OF SURFACE
BOUNDARY AND TIMING OF WAA PCPN WITH RETURN FLOW AS BOUNDARY MAKES A
RETURN AS A WARM FRONT. BETTER CHANCE FOR PCPN WEDNESDAY NIGHT WITH
STRONG FRONTOGENETIC RESPONSE TO 850-700 MB WAA.

.LONG TERM...THURSDAY THROUGH SUNDAY. FORECAST CONFIDENCE LOW

LOW CONFIDENCE FORECAST CONCERNING POPS AS MODELS VARY IN OVERALL
AMPLITUDE OF FEATURES OVER THE MIDDLE OF THE COUNTRY. A ZONAL FLOW
UNDER A BROAD WEAK 500 MB LOW OVER WESTERN ONTARIO BRINGING PERIODIC
VORT MAXES OVER THE REGION IS SHOWN ON THE GEM...WHILE THE GFS AND
ECMWF HOLD A DEEPER TROUGH OFF TO THE WEST...INDUCING WEAK RIDGING
OVER THE WESTERN LAKES WITH THE RESULTING SWLY FLOW DEFLECTING MOST
SHORT WAVE ENERGY TO THE NORTH AND WEST. HOWEVER ALL OF THE
SOLUTIONS KEEP PRECIP CHANCES IN THE FORECAST WITH AN 850 MB
BAROCLINIC ZONE WAVERING OVER THE AREA INTO THE WEEKEND. THEN LOW
CHANCE/SLIGHT CHANCE POPS THROUGH SUNDAY INTO MONDAY WITH LARGE
TIMING DIFFERENCES BETWEEN THE GFS AND ECMWF WITH PROGRESS OF
WESTERN TROUGH ACROSS THE UPPER MIDWEST. WARM FLOW BRINGS ABOVE
NORMAL TEMPS THE END OF THE WEEK INTO THE WEEKEND.

&&

.AVIATION/00Z TAFS/...

MVFR CEILINGS SHOULD GRADUALLY BECOME SCATTERED TO BROKEN AND VFR
CATEGORY BY 00Z MONDAY ACROSS MILWAUKEE AND KENOSHA. NORTHEAST WINDS
WILL LINGER INTO THIS EVENING...WITH SOME GUSTINESS AT MILWAUKEE AND
KENOSHA UNTIL SUNSET.

LIGHT WINDS AND A RELATIVELY MOIST AIRMASS ARE EXPECTED BY LATER
THIS EVENING INTO MONDAY MORNING. MODELS SHOWING ANOTHER BOUT OF LOW
STRATUS DEVELOPMENT...WITH SOME FOG...BETWEEN 09Z AND 15Z MONDAY AT
ALL SITES. CEILINGS AND VISIBILITIES SHOULD COME DOWN TO IFR/MVFR
CATEGORY DURING THIS PERIOD.

VFR CONDITIONS SHOULD RETURN BY LATE MORNING MONDAY...WITH MORE
SCATTERED TO BROKEN CUMULUS DEVELOPMENT DURING THE AFTERNOON. LOW
PRESSURE MOVING EAST TOWARD THE AREA SHOULD GRADUALLY BRING MIDDLE
TO HIGH CLOUDS INTO THE AREA DURING THE AFTERNOON AS WELL.

ANY SHOWERS AND STORMS SHOULD HOLD OFF AT MADISON UNTIL AFTER 00Z
TUESDAY...AND IN THE EAST UNTIL AFTER 03Z TUESDAY. LIGHT EAST TO
SOUTHEAST WINDS ARE EXPECTED AT THE EASTERN SITES MONDAY...WITH
LIGHT SOUTH WINDS AT MADISON.

&&

.MARINE...

NORTHEAST WINDS OF 10 TO 20 KNOTS WILL LINGER INTO THE EARLY EVENING
HOURS ACROSS THE NEARSHORE WATERS OF LAKE MICHIGAN. THIS WILL
CONTINUE TO BRING WAVES OF 2 TO 4 FEET DURING THIS TIME. WINDS AND
WAVES WILL DIMINISH BY LATER TONIGHT.

SHOULD SEE SOME FOG DEVELOPMENT OVER THE WATER TONIGHT...WITH
RELATIVELY LIGHT WINDS AND MOIST AIRMASS OVER THE AREA. LOW CLOUDS
DEVELOPING MAY LIMIT VISIBILITY VALUES.

&&

.BEACHES...

A MODERATE SWIM RISK WILL CONTINUE INTO EARLY THIS EVENING ACROSS
ALL OF THE BEACHES ALONG THE LAKE MICHIGAN SHORELINE. NORTHEAST
WINDS OF 1O TO 20 MPH...WITH WAVES OF 2 TO 4 FEET...MAY LEAD TO
DIFFICULT SWIMMING CONDITIONS AT TIMES. THERE IS ALSO THE
POSSIBILITY FOR DANGEROUS CURRENTS DEVELOPING. WINDS AND WAVES WILL
DIMINISH BY LATER TONIGHT.

&&

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

$$

TONIGHT/MONDAY AND AVIATION/MARINE...WOOD
MONDAY NIGHT THROUGH SUNDAY...REM


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