Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 111948
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
248 PM CDT FRI APR 11 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND SATURDAY
ISSUED AT 248 PM CDT FRI APR 11 2014

THE LATEST RUC ANALYSIS AND RADAR/SATELLITE IMAGERY SHOW A WEAK
SHORTWAVE TROUGH MOVING ACROSS WISCONSIN THIS AFTERNOON...AND IS
HELPING TO KICK OFF LIGHT RAIN SHOWERS FROM MARINETTE TO WISCONSIN
RAPIDS.  TEMPS HAVE BEEN HELD BACK BECAUSE OF THE RAIN OVER N-C
WISCONSIN WHERE READINGS REMAIN IN THE LOWER TO MIDDLE 40S.
ANTICIPATE THIS SHORTWAVE AND SHOWER ACTIVITY TO BE EXITING THE
REGION BY LATE THIS AFTERNOON...AND A PARTIAL CLEARING TREND SHOULD
THEN TAKE PLACE HEADING INTO THIS EVENING.  THEN ATTENTION TURNS TO
THE NORTHERN PLAINS WHERE MID AND HIGH CLOUDS ARE ALREADY MOVING
ACROSS THE WESTERN DAKOTAS AHEAD OF THE NEXT LOW PRESSURE SYSTEM.
TIMING RAIN CHANCES AND AMOUNTS WITH THIS SYSTEM ARE THE MAIN
FORECAST CONCERNS IN THE SHORT TERM.

TONIGHT...SHORTWAVE ENERGY MOVING ACROSS MONTANA AND NORTH DAKOTA
WILL GENERATE SURFACE LOW PRESSURE THAT WILL SHIFT ACROSS SOUTH
DAKOTA.  AHEAD OF BOTH FEATURES...A LLJ UPWARDS OF 50 KTS WILL BE
DEVELOPING AND SHIFTING EAST TOWARDS THE MISSISSIPPI VALLEY BY 12Z
SATURDAY.  MOISTURE TRANSPORT WILL BE VERY GOOD WITHIN THE
LLJ...ADVECTING PWATS GREATER THAN 0.75 INCHES INTO THE NORTHERN
MISSISSIPPI VALLEY.  AS A RESULT...SHOULD SEE AN AREA RAIN DEVELOP
ON THE NOSE OF THE LLJ AND PUSH EAST ACROSS CENTRAL MINNESOTA AND
INTO FAR NORTHWEST WISCONSIN BY LATE TONIGHT.  A POSSIBILITY THAT
SOME RAIN CAN SNEAK INTO CENTRAL AND NORTH-CENTRAL WISCONSIN BY
DAYBREAK...AND WILL LEAVE A CHANCE IN THE FORECAST.
OTHERWISE...SHOULD SEE A BRIEF PERIOD OF MOSTLY CLEAR TO PARTLY
CLOUDY CONDITIONS THIS EVENING ONCE WEAK SHORTWAVE ENERGY AND RAIN
SHOWERS EXIT.  THEN CLOUDS WILL BE INCREASING LATE THIS EVENING AND
THROUGH THE OVERNIGHT.  LOWS RANGING FROM THE LOWER 30S NORTH TO
LOWER 40S SOUTH.

SATURDAY...LOW PRESSURE WILL MOVE EAST ACROSS SOUTHERN MINNESOTA.
NOSE OF THE WELL-DEVELOPED LLJ WILL BE LIFTING EAST-NORTHEAST ACROSS
THE STATE OF WISCONSIN ALONG THE 850MB THETAE GRADIENT.  MOISTURE
TRANSPORT WILL REMAIN VERY GOOD WITHIN THE LOW LEVEL JET...WITH
PWATS INCREASING TO GREATER THAN AN INCH OVER EAST-CENTRAL WISCONSIN
BY SATURDAY AFTERNOON.  MODELS ADD A LITTLE UNCERTAINTY HOW PRECIP
WILL EVOLVE TOMORROW...AS A RESULT OF INCREASING ELEVATED
INSTABILITY OVER CENTRAL AND SOUTHERN PARTS OF THE STATE.  LEANING
TOWARD AN AREA OF RAIN FOLLOWING THE NOSE OF THE LLJ AND LIFTING
NORTHEAST ACROSS NORTH-CENTRAL AND NORTHEAST WISCONSIN.
REDEVELOPMENT OF SHOWERS IS POSSIBLE OVER EAST-CENTRAL WISCONSIN
DURING THE AFTERNOON.  CANNOT RULE OUT A FEW THUNDERSTORMS GIVEN THE
MAGNITUDE OF THE FORCING AND MID-LEVEL LAPSE RATES UPWARDS OF 6.5
C/KM...MAINLY SOUTH OF A MERRILL TO STURGEON BAY LINE.  RAIN AMOUNTS
LOOK TO BE AROUND A HALF AN INCH AT SPOTS...WHICH IS NOT QUITE HIGH
ENOUGH FOR AN ISSUANCE OF AN AREAL FLOOD WATCH.  HIGHS RANGING FROM
THE MID 40S NORTH TO THE LOWER 60S SOUTH.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
ISSUED AT 248 PM CDT FRI APR 11 2014

MAIN FCST CONCERNS INCLUDE PCPN TRENDS FOR THE WEEKEND INTO EARLY
MONDAY...AND THE THREAT OF HEAVY RAINFALL...THUNDERSTORMS...AND
EVENTUALLY ACCUMULATING SNOW SUNDAY NIGHT INTO EARLY MONDAY.

MODELS HAVE BACKED OFF ON QPF AMOUNTS ON SATURDAY NIGHT...WITH ONLY A
QUARTER TO HALF OF RAIN EXPECTED IN THE SE PORTION OF THE FORECAST
AREA...AND MUCH LESS FARTHER NW. WILL KEEP A CHANCE OF ELEVATED TSTMS
IN THE FCST...ESPECIALLY IN THE EVG. EXPECT A DECREASING TREND IN THE
SHOWER ACTIVITY OVERNIGHT INTO SUNDAY MORNING.

SHOWERS SHOULD INCREASE RAPIDLY AGAIN LATE SUNDAY INTO SUNDAY NIGHT...
AS A SFC WAVE LIFTS NORTH ALONG THE SLOW MOVING FRONT...AND
DYNAMICS RAMP UP DUE TO THE RRQ OF AN UPPER LEVEL JET AND DEEP
FRONTOGENETIC FORCING. THIS PERIOD OF RAIN SHOULD BE MORE SIGNIFICANT...
WITH QPF AMOUNTS OF A HALF INCH TO AN INCH ACROSS THE SE THIRD OF
GRB CWA. COLD AIR WILL WORK ITS WAY SE ACROSS THE FCST AREA SUNDAY
NIGHT...CAUSING THE RAIN TO MIX WITH THEN CHANGE OVER TO SNOW. SNOW
WILL PULL OUT OF EASTERN WI MONDAY MORNING. RIGHT NOW...ONLY EXPECTING
1 TO 2 INCHES OF ACCUMULATION IN MOST PLACES...BUT WILL NEED TO KEEP
AN EYE ON THE FOX VALLEY AND LAKESHORE AREAS...IN THE EVENT THE SNOW
IS SLOWER TO EXIT THE REGION MONDAY MORNING.

CHILLY CONDITIONS WILL AFFECT THE REGION FROM MONDAY THROUGH
WEDNESDAY...FOLLOWED BY SLIGHT MODERATION INTO THURSDAY. THERE
WILL BE A CHANCE OF LIGHT MIXED PCPN FROM WEDS NGT INTO FRIDAY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1229 PM CDT FRI APR 11 2014

A WEAK DISTURBANCE WILL PASS OVER THE CENTRAL AND
EASTERN PARTS OF THE STATE EARLY THIS AFTERNOON AND WILL GENERATE
SCATTERED LIGHT SHOWERS THAT COULD DROP VSBYS INTO MVFR RANGE
BRIEFLY.  A PERIOD OF CLEARING WILL THEN OCCUR ONCE THE WEAK
DISTURBANCE DEPARTS LATER THIS AFTERNOON.  THEN A POTENT STORM
SYSTEM WILL BE GATHERING STRENGTH ACROSS THE NORTHERN PLAINS
TONIGHT.  CLOUDS WILL BE BUILDING AND LOWERING THROUGH THE NIGHT AS
THE SYSTEM MOVES CLOSER.  RAIN WILL ARRIVE ACROSS THE REGION EARLY
TO MID-MORNING...WITH CIGS/VSBYS DROPPING QUICKLY WHEN THE RAIN
ARRIVES.
&&

.HYDROLOGY...
ISSUED AT 248 PM CDT FRI APR 11 2014

CONSIDERED ISSUING AN AREAL FLOOD WATCH FOR AREAS SOUTH OF A LINE
FROM MERRILL TO MARINETTE...BUT DECIDED TO HOLD OFF FOR NOW...SINCE
PCPN AMOUNTS ARE NOT EXPECTED TO BE AS HIGH AS EARLIER THOUGHT ON
SATURDAY AND SATURDAY NIGHT. WE ARE STILL ANTICIPATING SOME HEAVY
PCPN OVER EAST CENTRAL WI LATE SUNDAY INTO SUNDAY NIGHT...WITH A
HALF INCH TO AN INCH OVER THE FOX VALLEY AND LAKESHORE AREAS. WILL
LET THE HYDRO FOCAL POINT TAKE A CLOSER LOOK AT THE SITUATION
TONIGHT...AND ASSESS WHETHER A FLOOD WATCH IS WARRANTED FOR LATER IN
THE WEEKEND. WILL CONTINUE WITH AN ESF FOR NOW.
&&

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

$$

SHORT TERM.....MPC
LONG TERM......KIECKBUSCH
AVIATION.......MPC
HYDROLOGY......KIECKBUSCH






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