Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 291927
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
227 PM CDT FRI MAY 29 2015

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND SATURDAY
ISSUED AT 227 PM CDT FRI MAY 29 2015

THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A STRONG
COLD FRONT MOVING ACROSS NORTHWEST WISCONSIN EARLY THIS AFTERNOON.
SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE TO DEVELOP AHEAD OF THE
FRONT WITH HELP FROM WEAK SHORTWAVES...ONE OVER SOUTHWEST
WISCONSIN...AND ANOTHER OVER SOUTHERN MINNESOTA.  AS THE WAVE OVER
SOUTHEAST WISCONSIN LIFTS NORTHEAST...SCATTERED STORMS SHOULD SPREAD
ACROSS THE FOX VALLEY AND LAKE SHORE AREAS WHERE ML CAPES ARE
BUILDING TO GREATER THAN 400 J/KG.  SHOWERS AND A FEW THUNDERSTORMS
WILL ALSO BECOME MORE WIDESPREAD OVER N-C WISCONSIN AHEAD OF THE
FRONT THIS AFTERNOON.  GUSTY WINDS AND SMALL HAIL WILL BE POSSIBLE
WITHIN ANY STORMS...ALONG WITH A POTENTIAL QUICK INCH OF RAIN. WITH
A JUICY AIRMASS IN PLACE...PRECIP TRENDS AND AMOUNTS ARE THE MAIN
FORECAST CONCERNS AS THE FRONT SLOWLY MOVES ACROSS THE REGION.

TONIGHT...THE STRONG COLD FRONT WILL MOVE SOUTHEAST ACROSS CENTRAL
AND NORTHEAST WISCONSIN DURING THE EVENING.  AHEAD OF THE
FRONT...SCATTERED SHOWERS AND THUNDERSTORMS WILL BE OCCURRING IN AN
AREA OF DIMINISHING INSTABILITY.  IN ADDITION...THERE WILL BE A
MINIMUM OF SHEAR RIGHT AHEAD OF THE FRONT.  SO POTENTIAL FOR ANY
SEVERE WEATHER REMAINS LOW...BUT GUSTY WINDS TO 40 MPH AND SMALL
HAIL LOOKS REASONABLE WITHIN ANY THUNDERSTORMS.  BEHIND THE
FRONT...STRONG MID-LEVEL FGEN COMBINED WITH UPPER DIVERGENCE IN THE
RIGHT REAR QUAD OF AN UPPER JET...AND PWATS IN EXCESS OF 1.50 WILL
LEAD TO A BAND OF MODERATE TO HEAVY RAIN SLOWLY MOVING ACROSS THE
FORECAST AREA.  THE SLOW MOVEMENT OF THE RAIN WITH SOME INTERACTION
FROM DAYTIME INSTABILITY LEADS ME TO THINK THE HIGHEST RAINFALL
TOTALS WILL BE ACROSS NORTH-CENTRAL WISCONSIN WHERE A WIDESPREAD
INCH...LOCALLY UP TO 2 INCHES WITHIN THUNDERSTORMS...COULD FALL.
ELSEWHERE...A WIDESPREAD HALF INCH TO INCH LOOKS REASONABLE.  NORTH
WINDS WILL BECOME GUSTY LATE BEHIND THE FRONT AS COLDER AIR RUSHES
IN.  LOWS RANGING FROM THE LOWER 40S NORTH TO MID 50S SOUTH.

SATURDAY...THOUGH THE FRONT WILL BE EXITING THE REGION BY THE START
OF SATURDAY MORNING...RIGHT REAR QUAD OF THE UPPER JET AND MID-LEVEL
FGEN WILL BE HANGING OVER EASTERN WISCONSIN.  HAVE INCREASED PRECIP
CHANCES THERE FOR THE MORNING.  MODELS ARE ALSO SLOWER EXITING
PRECIP IN THE AFTERNOON...AND HAVE KEPT A SMALL CHANCE OVER EAST-
CENTRAL WISCONSIN THROUGH 21Z.  AS A COLD CANADIAN AIRMASS BUILDS
INTO THE REGION...TEMPERATURES WILL BE SIGNIFICANTLY COOLER THAN
TODAYS READINGS.  WITH BLUSTERY CONDITIONS...HIGHS WILL RANGE FROM
THE MID 50S NORTH TO LOW 60S SOUTH.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
ISSUED AT 227 PM CDT FRI MAY 29 2015

THE POTENTIAL FROST AND FREEZE HEADLINES WILL BE THE PRIMARY
ISSUE THIS WEEKEND AS A VERY COOL DRY HIGH PRESSURE SYSTEM WILL
DRIFT OVER THE GREAT LAKES REGION IN THE WAKE OF A STRONG COLD
FRONT. NEXT PCPN CHANCES FOR NEXT WEEK WILL BE THE NEXT ISSUE AS
TEMPERATURES GRADUALLY WARM.

THE RIDGE AXIS OF THE A CANADIAN HIGH PRESSURE SYSTEM IS PROGGED
TO BE OVER NORTHERN WISCONSIN DURING THE LATE SATURDAY NIGHT
HOURS. THE LIGHT WINDS...CLEAR SKIES...DRY AIR AND H850 TEMPS LESS
THAN +2 C PROVIDE A LIKELY SCENARIO OF FROST OR FREEZING
TEMPERATURES. ANTICIPATE A HEADLINE WILL BE NEEDED IN THE NEXT 24
HOURS AFTER DEALING WITH THE STRONG COLD FRONT AND CONVECTION.
AIR MASS MAY STILL SUPPORT SOME FROST OVER THE FAR NORTHEAST
SUNDAY NIGHT BUT NOT AS WIDESPREAD.

TEMPERATURES WILL GRADUALLY WARM FOR THE START OF THE NEW WEEK AS
AN UPPER RIDGE SETTLES OVER THE GREAT LAKES REGION. THE CANADIAN
SURFACE HIGH WILL CONTINUE TO RIDGE INTO THE REGION WHILE THE RETURN
WARM AIR ADVECTION FLOW AND CHANCES OF CONVECTION IS PRIMARILY
CONFINED TO THE NORTHERN PLAINS IN THE SOUTHWEST FLOW OF A BROAD
UPPER TROUGH OVER THE WESTERN STATES. SOME DEBRIS CLOUDS FROM THIS
NORTHERN PLAINS CONVECTION MAY BE ABLE TO DRIFT INTO NORTHERN
WISCONSIN MONDAY AND TUESDAY TO AFFECT TEMPERATURES.

CONVECTION MAY BEGIN TO SPREAD INTO AT LEAST THE NORTHWEST PORTION
OF WISCONSIN ON WEDNESDAY AND THURSDAY WITH THE UPPER RIDGE
PROGGED TO SHIFT A BIT MORE EAST. RETURN FLOW 850 WARM AIR
ADVECTION CONTINUES TO INCREASE OVER THE NORTHERN PLAINS AS WELL
AS INTO THE FAR WESTERN GREAT LAKES REGION. EASTERN SECTIONS MAY
CONTINUE TO BE PROTECTED BY THE DEPARTING HIGH PRESSURE SYSTEM SO
HIGH PCPN CHANCES WILL BE CONFINED OVER THE NORTHWEST. PROGS IN
SOME AGREEMENT WITH THE UPPER RIDGE SUBSIDING AND A RETURN TO A
SOUTHWEST FLOW ALOFT AND PCPN CHANCES SPREADING EASTWARD LATE NEXT
WEEK.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1214 PM CDT FRI MAY 29 2015

A STRONG COLD FRONT WILL MOVE ACROSS THE TAF SITES LATE
THIS AFTERNOON AND THIS EVENING.  AHEAD OF THE FRONT...SCATTERED
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON.  SHOWERS
AND STORMS ARE EXPECTED TO BECOME MORE WIDESPREAD RIGHT ALONG AND
ALSO BEHIND THE FRONT.  HEAVY RAIN WILL BE POSSIBLE WITHIN ANY
THUNDERSTORMS.  AS THE RAIN INTENSITY INCREASES...UPSTREAM OBS SHOW
CIGS FALLING TO IFR BEHIND THE FRONT.  THE RAIN WILL CONTINUE INTO
THE OVERNIGHT HOURS...BEFORE ENDING LATE TONIGHT OVER CENTRAL AND
NORTH-CENTRAL WISCONSIN...AND BY LATE MORNING OR EARLY AFTERNOON
OVER EASTERN WISCONSIN.
&&

.HYDROLOGY...
ISSUED AT 227 PM CDT FRI MAY 29 2015

MOST RIVERS LEVELS PRIOR TO THE NEXT ROUND OF RAIN TODAY/TONIGHT
WERE MAINLY STEADY OR SLOWLY FALLING. AN ANTICIPATED WIDESPREAD 1
INCH RAINFALL THROUGH SATURDAY MORNING WILL REVERSE THAT TREND
WITH SOME RIVERS LIKELY RISING TO NEAR FS AND PERHAPS A FEW
EXCEEDING INTO THE MINOR FS LEVELS BY SATURDAY MORNING. LOCALLY
HIGHER 2 INCHES AMOUNTS POSSIBLE WITH THUNDERSTORMS. ISOLATED TO
SCATTERED STORMS WITH LOCALLY HEAVY RAINFALL ANTICIPATED AHEAD OF
THE COLD FRONT THROUGH THIS EVENING. A MORE WIDESPREAD 1 INCH
RAINFALL IN THE WAKE OF THE COLD FRONT OR POST FRONTAL REGION...WITH
LOCALLY HIGHER AMOUNTS OF 2 INCHES DUE TO EMBEDDED STORMS.



TDH.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......MPC
HYDROLOGY......TDH



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