Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 220212
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
912 PM CDT THU MAY 21 2015

.UPDATE...SCATTERED SHOWERS SHOWING A DIMINISHING TREND LAST 30
MINUTES OR SO...BUT AT LEAST ISOLATED SHOWERS SHOULD CONTINUE
NEXT SEVERAL HOURS AS LOW LEVEL FRONTOGENETICAL FORCING SLIDES
THROUGH SOUTHEAST WI. GUSTY NORTH TO NORTHEAST IN WAKE OF BACKDOOR
COLD FRONT CURRENTLY MOVING THROUGH MILWAUKEE WILL SLIDE SOUTH
THROUGH REST OF CWA THROUGH 09Z OR SO. OVERNIGHT TEMPS LOOK IN
GOOD SHAPE.

&&

.AVIATION/06Z TAFS/...SCATTERED SHOWERS WILL DIMINISH THROUGH
MIDNIGHT ACROSS SOUTHEAST WI AS LOW LEVEL FRONTOGENETICAL FORCING
WEAKENS AND SLIDES SOUTH OF THE AREA. GUSTY NORTHEAST WINDS WILL
AFFECT ERN TAF SITES FOR SEVERAL HOURS BEFORE SETTLING DOWN. VFR
CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD.

&&

.MARINE...COLD FRONT ACCELERATING SOUTH ACROSS THE NEARSHORE
WATERS IS OVER NORTHERN LMZ645 AND WILL SWEEP SOUTH ACROSS THE
REST OF LMZ645 AND LMZ646 THRU 04-05Z. SOUTHWEST WINDS ABRUPTLY
VEER TO THE NORTHEAST WITH A FEW GUSTS TO 25 TO 30 KNOTS IN ITS
WAKE. EXPECT 1-3 HOURS OF GUSTY WINDS BEFORE THEY SETTLE DOWN. DUE
TO EXPECTED BRIEF NATURE OF THE GUSTINESS...WL HOLD OFF ON SMALL
CRAFT ADVY. CONSULT LATEST MARINE WEATHER STATEMENT FOR MORE
DETAILS. WAVES WILL BRIEFLY RISE TO 2 TO 4 FEET IN GUSTY ONSHORE
FLOW BEFORE SETTLING SUBSIDING.

&&

.PREV DISCUSSION... /ISSUED 323 PM CDT THU MAY 21 2015/

TONIGHT - CONFIDENCE...MEDIUM
DRY AND MILD WESTERLY FLOW WILL PERSIST INTO THE EARLY EVENING
HOURS. FRONTAL BOUNDARY THEN PROGGED TO SWEEP SOUTH AND SHIFT
WINDS TO THE NE. ALREADY SEEING SOME NORTHERLY 20 KNOT PLUS GUSTS
ACRS NRN WI WITH WEAK POST FRONTAL PRESSURE RISES VCNTY U.P. SO NE
GUSTINESS EXPECTED ESPECIALLY NEAR LAKE MICHIGAN. WILL LEAVE
MENTION OF A FEW SHRA IN PARTS OF THE ERN CWA THIS EVENING. KGRB
RADAR SHOWS A FEW SHRA POPPING UP WITHIN AGITATED CU FIELD VCNTY
FRONTAL BOUNDARY. HIGH PRESSURE SETTLES IN LATER IN THE NIGHT.

FRIDAY - CONFIDENCE...HIGH
SURFACE HIGH PRESSURE EXPECTED TO DOMINATE WITH PLENTY OF SUNSHINE AND
LIGHT WIND REGIME. ONSHORE COMPONENT WILL KEEP THE EAST COOLER. 925
TEMPS RISE TO AROUND 9C IN THE EAST AND 14C IN THE WEST...SO EXPECT
A DECENT EAST/WEST GRADIENT IN TEMPS.

SHORT TERM...FRIDAY NIGHT THROUGH SUNDAY NIGHT.

FRIDAY NIGHT AND SATURDAY...FORECAST CONFIDENCE HIGH

SURFACE HIGH CENTERED OVER LOWER MICHIGAN SHIFTS SLOWLY TO THE
SOUTHEAST AND EXPANDS. WARMING 850 MB TEMPS AS COLD POOL MOVES EAST
WITH DEPARTING SRN CANADIAN CLOSED LOW...AND 500 MB HEIGHTS SLOWLY
RISE AS DEEPENING TROUGH MOVES INTO WESTERN U.S. WILL SEE LOWS HOLD
IN THE UPPER 40S IN THE SW THIRD...WITH LOW TO MID 40S ELSEWHERE.

SOME 700 MB MOISTURE AND OMEGA MOVE ACROSS WESTERN WI SATURDAY
AFTERNOON...BUT STRONGER Q-VECTOR CONVERGENCE STAYS TO THE WEST WITH
MORE FOCUSED 850 MB WARM AIR ADVECTION AND LOWER CONDENSATION
PRESSURE DEFICITS. SOUNDINGS ARE ALSO DRY BELOW 5K FT REFLECTING
INFLUENCE OF LOBE OF SURFACE HIGH PRESSURE EXTENDING WESTWARD OVER
SRN WI FROM BROAD HIGH CENTERED OVER THE MID-ATLANTIC STATES. NO
MORE THAN SLIGHT POPS WARRANTED AND WILL KEEP LIMITED TO THE FAR NW.
SOME DIFFERENCES IN HOW WARM 925 MB TEMPS GET SO CONSENSUS HIGHS IN
THE LOWER 70S AWAY FROM LAKE MICHIGAN LOOK GOOD WITH UPPER 60S
LAKESIDE.

SATURDAY NIGHT...FORECAST CONFIDENCE HIGH

JET SHIFTS NWD WITH UPPER RIDGING DEVELOPING OVER CENTRAL SECTIONS
OF THE COUNTRY IN RESPONSE TO DEEP FULL-LATITUDE TROUGH DIGGING INTO
THE SW U.S. PCPN CHANCES ARE PREDICATED ON TIMING OF PRECURSOR SHORT
WAVES EJECTING AHEAD OF DEEP WESTERN U.S. TROUGH AND LIFTING TOWARD
THE WESTERN GREAT LAKES IN MOIST SLY FLOW.

FIRST SHORT WAVE APPROACHES...WITH TIMING DIFFERENCES CAUSING PCPN
CHANCES THROUGH 12Z SUNDAY TO RANGE FROM KEEPING THE ENTIRE CWA
DRY/12Z GFS/...TO BRINGING PCPN INTO THE WEST OR FAR SOUTH/NAM AND
12ZECMWF/...OR OVER ALL BUT THE FAR NORTH AND EAST/12Z CANADIAN.
WILL FOLLOW CONSENSUS POPS WHICH LIMITS CHANCE POPS TO THE SOUTH
CENTRAL AND SLIGHT CHANCE ELSEWHERE WITH LESS THAN 15 PCT IN THE FAR
SOUTHEAST. LOWS WILL HOLD IN THE 50S OVERNIGHT WITH RISING 925 MB
TEMPS

SUNDAY AND SUNDAY NIGHT...FORECAST CONFIDENCE MEDIUM

ALL MODELS SWING INITIAL SHORT WAVE ACROSS SRN WI SUNDAY
MORNING...WITH ANOTHER WARM ADVECTION SURGE APPROACHING THE FAR
SOUTH BY 00Z MONDAY. HIGHER RESOLUTION VERSIONS OF GFS AND NAM
INDICATE THERE WILL PROBABLY SEE A BREAK IN THE PCPN BETWEEN THESE
TWO ROUNDS...BUT MODEL TIMING UNCERTAINTY LEADS TO POPS ALL DAY IN
THE CONSENSUS POPS. BETTER POPS SUNDAY NIGHT WITH WARM ADVECTION
SURGE. HOPEFULLY LATER RUNS WILL LEAD TO BETTER RESOLUTION TO PCPN
TIMING.

IF BREAK IN PCPN IS LONG ENOUGH...AND A BIT OF SUN CAN POP
THROUGH...COULD SEE TEMPS RISE HIGHER THAN UPPER 60S TO LOWER 70S
WITH FORECAST 925 MB TEMPS. INSTABILITY IN SOUNDINGS NOT THAT
IMPRESSIVE SO WILL LIMIT CHANCES OF THUNDER. LOWS WILL ONLY COOL
INTO THE UPPER 50S TO AROUND 60 NEAR THE IL BORDER.

LONG TERM...MONDAY THROUGH THURSDAY...FORECAST CONFIDENCE MEDIUM

AN UNSETTLED AND WET PERIOD IN OVERALL SWLY MID TO UPPER LEVEL FLOW
AS WESTERN TROUGH MOVES OUT INTO THE PLAINS MONDAY...AND THEN
DAMPENS AS IT CROSSES THE UPPER MIDWEST TUESDAY AND IS ABSORBED INTO
A CLOSED LOW OVER HUDSON BAY. MOIST SRLY SURFACE FLOW CONTINUES AS
SURFACE LOW PASSES BY TO THE WEST AND NORTH OF THE STATE. GFS AND
ECMWF BRING ANOTHER SURGE OF MOISTURE WITH A SHORT WAVE TUESDAY
NIGHT...WITH THE GFS DEVELOPING A SURFACE LOW THAT MOVES RIGHT ACROSS
THE STATE WEDNESDAY. ECMWF DRIES AREA OUT WEDNESDAY INTO
THURSDAY...WITH ANOTHER WAVE MOVING IN FOR THURSDAY AFTERNOON/NIGHT.
GFS KEEPS AREA DRY ONCE PCPN ENDS WEDNESDAY EVENING. RESULT IS
CHANCE POPS THROUGH THE EXTENDED WITH BLENDED SOLUTION. LOOKING FOR
ABOVE NORMAL TEMPERATURES THROUGH THE EXTENDED.

AVIATION/00Z TAFS/...VFR THIS PERIOD WITH WESTERLY SURFACE FLOW
AHEAD OF FRONT DROPPING SOUTHWARD FROM NRN WI. PREFER THE DRIER LOOK
OF THE HRRR WITH RESPECT TO PRECIP COVERAGE. LATEST GUIDANCE
SUGGESTS FRONT DROPS THROUGH TAF SITES BETWEEN 01Z-03Z. BRIEF PERIOD
OF GUSTY NE WINDS POSSIBLE. HAVE ALSO KEPT THE EVENING POPS WITH
THIS FEATURE AS WELL. NAM/RAP SOUNDINGS SHOW LITTLE POTENTIAL FOR
POST FRONTAL MVFR CIGS. QUIET HIGH PRESSURE DOMINATES FOR FRIDAY.

MARINE...A COLD FRONT WILL RACE DOWN THE LAKE EARLY THIS
EVENING...REACHING SHEBOYGAN AROUND 7 PM AND KENOSHA BY 9-10PM THIS
EVENING. WINDS WILL SHIFT ABRUPTLY FROM WESTERLY TO NORTHEAST AND
MAY GUST TO AROUND 20KTS POST FROPA FOR A TIME BEFORE SETTLING BACK
DOWN.

&&

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

$$

UPDATE...MBK


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