Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 302002
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
302 PM CDT MON MAR 30 2015

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SYNOPSIS...
ISSUED AT 302 PM CDT MON MAR 30 2015

SOME LIGHT MIXED PRECIPITATION TONIGHT...THEN SHOWERS AND POSSIBLY
SOME THUNDERSTORMS WEDNESDAY NIGHT INTO THURSDAY.

PROGRESSIVE AND ENERGETIC BAND OF WESTERLIES WILL CONTINUE ACRS
MUCH OF THE CONUS AND SRN CANADA THROUGHOUT THE PERIOD. THE
AMPLITUDE OF THE LARGE SCALE PATTERN WL REMAIN LIMITED FOR MOST IF
NOT ALL OF THE FCST PERIOD. THAT WL RESULT IN WX PRIMARILY BEING
CONTROLLED THE SYNOPTIC SYSTEMS MIGRATING ACRS THE CONUS...WITH
CONSIDERABLE DAILY TEMPERATURE VARIATIONS DUE TO THE PASSAGE OF
EACH SYSTEM. OVERALL...READINGS WL PROBABLY END UP AVERAGING A
LITTLE ABV NORMAL FOR THE PERIOD. THERE WL BE ENOUGH OPPORTUNITIES
AND SUFFICIENT AVAILABLE MOISTURE TO RESULT IN NR NORMAL PCPN FOR
THE PERIOD.
&&

.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 302 PM CDT MON MAR 30 2015

MAIN FORECAST CONCERN WILL BE THE UPPER LEVEL DISTURBANCE MOVING
THROUGH TONIGHT.

AFTERNOON SURFACE ANALYSIS SHOWED A WEAK AREA OF LOW PRESSURE
MOVING INTO WESTERN MINNESOTA. THIS SYSTEM WILL PUSH INTO
NORTHEAST WISCONSIN TONIGHT AS IT COUPLES WITH AN UPPER LEVEL
SHORTWAVE AND JETSTREAK...BRINGING WITH IS THE CHANCE FOR
PRECIPITATION. MODELS HAVE TRENDED SOUTH WITH THE TRACK OF THE LOW
AND PRECIPITATION...MAINLY MOVING ALONG AN 850MB BAROCLINIC ZONE.
COMPARING CURRENT 850MB TEMPERATURES...PRECIPITATION TRENDS OVER
THE PAST 6 HOURS...AND SFC LOW POSITIONS TO MODEL SOLUTIONS FOR
18Z MONDAY...SEEMS LIKED THE NAM12 AND GFS WERE HANDLING THE
DEVELOPMENT OF THIS SYSTEM THE BEST. LEANED TOWARDS A BLEND OF
THESE SOLUTIONS FOR THE OVERNIGHT FORECAST. THIS LOWERED
PRECIPITATION CHANCES IN THE NORTH AND NORTHEAST CORNER. THIS
MATCHED UP WELL FORCING COMING THROUGH AS THE SHORTWAVE SWINGS
SOUTHEAST THROUGH THE STATE. LOOKS LIKE THE BEST CHANCE FOR
PRECIPITATION WILL BE IN CENTRAL WI TOWARDS HE FOX VALLEY AND
THE CENTRAL LAKESHORE AROUND 06Z TONIGHT AS THE BEST FORCING AND
MOISTURE MOVES THROUGH. AFTER 06Z...MOVED PRECIP AREA TO THE
NORTHEAST AND DIMINISHED CHANCES TOWARDS DAYBREAK.

WHILE PRECIPITATION SHOULD START OFF AS RAIN ACROSS THE CWA...A
CHANGE OVER IS EXPECTED IN THE FAR NORTH AND NORTHEAST. KEPT CLOSE
TO PREVIOUS FORECAST WITH PRECIP TRANSITION. WHILE MODEL GUIDANCE
HAD TRENDED WARMER AT THE SURFACE...MIDLEVELS WERE COOLER ON ALL
THE MODELS WITH ADDED EVAPORATIONAL COOLING. A MIXTURE OF RAIN AND
SNOW...THEN A CHANGE TO ALL SNOW WILL START IN THE FAR NORTHEAST
AROUND 03Z TONIGHT...AND GRADUAL WORK ITS WAY SOUTHWEST THROUGH
THE NIGHT. AREAS NORTH OF A WAUSAU TO GREEN BAY LINE SHOULD REMAIN
ALL RAIN THROUGH AT LEAST 09Z TUESDAY BEFORE MIXING WITH SNOW
TUESDAY MORNING. NOT MUCH ACCUMULATION IS EXPECTED...WITH AROUND
AN INCH POSSIBLE TO THE NORTH.

PRECIPITATION SHOULD COME TO AN END IN MOST LOCATION THROUGH
TUESDAY MORNING. LIGHT PRECIP IS STILL POSSIBLE IN NORTHERN
WISCONSIN AS ANOTHER WEAK IMPULSE MOVES THROUGH THE MEAN UPPER
LEVEL FLOW. MODELS ARE HAVING AN ISSUE RESOLVING THIS FEATURE AND
THEREFORE DO NOT AGREE ON PRECIPITATION CHANCES. LOWERED CHANCES A
BIT IN THE AFTERNOON AS ANY FORCING THAT MOVES THROUGH SHOULD BE
QUICK HITTING AND SHORT LIVED.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 302 PM CDT MON MAR 30 2015

THE MAIN WEATHER MAKER WILL BE THE CYCLONE AND ASSOC FRONTAL
SYSTEMS CROSSING THE REGION MID-WEEK. MODELS HAVE TRENDED A LITTLE
SLOWER WITH THE ARRIVAL OF THE PCPN WITH THE SYSTEM COMPARED TO
YDA...SO ADJUSTED THE FCST ACCORDINGLY. WITH THE PCPN BAND NOW
ARRIVING LATE IN THE NGT...SOME OF THE MODELS SUGGEST IT MAY BE
DISSIPATING AS IT CROSSES THE RGN. THAT WOULD BE MORE TYPICAL OF A
SYSTEM LATER IN THE WARM SEASON...WHEN FORCING IS TYPICALLY
WEAKER. FORCING FM THE SHRTWV STILL LOOKS PRETTY STG...SO CARRIED
LIKELY POPS ACRS THE RGN...THOUGH DID NOT PLACE THEM IN THE E
UNTIL THURSDAY MORNING. THE SPC DAY 3 CONVECTIVE OUTLOOK ISSUED
EARLY THIS MORNING CARRIED A MARGINAL RISK OF SVR INTO FAR WRN
WI...AND GENERAL THUNDER ACRS THE AREA. MID-LVL LAPSE RATES
PROGGED TO BE FAIRLY STEEP...SO HELD ON TO MENTION OF THUNDER
DESPITE THE LATER ARRIVAL OF THE MAIN PCPN BAND.

TEMPS TAKEN FROM BLEND OF TOP PERFORMING GUIDANCE PRODUCTS...WITH
SOME EXTRA WEIGHT ON THE ECMWF/ECMWF MOS AND THEIR RELATED BIAS-
CORRECTED PRODUCTS.

THE REMAINDER OF THE FORECAST IS DOMINATED BY SMALLER/WEAKER
SHRTWVS EMBEDDED IN THE FAIRLY LOW-AMPLITUDE LARGE SCALE FLOW. AS
SUCH...TIMING AND PLACEMENT WAS QUITE DIFFERENT AMONG THE MODELS.
GIVEN THE PATTERN...STUCK WITH THE STANDARD EXTENDED FORECAST
INITIALIZATION GRIDS BASED ON A BROAD BLEND OF GUIDANCE PRODUCTS.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1209 PM CDT MON MAR 30 2015

CLOUDS WILL INCREASE ACROSS THE AREA THIS AFTERNOON AS A WEAK
DISTURBANCE MOVES INTO THE STATE...HOWEVER CIGS SHOULD STAY IN THE
VFR CATEGORY FOR MUCH OF THE AFTERNOON. THERE IS A CHANCE FOR
LIGHT RAIN THIS AFTERNOON IN CENTRAL TAF SITES...BUT THE REST OF
THE AREA SHOULD REMAIN DRY UNTIL THIS EVENING. THIS SYSTEM WILL
THEN OVERSPREAD LIGHT RAIN AND SNOW TO THE AREA TONIGHT WITH
CEILINGS AND VISIBILITY LOWERING TO IFR CONDITIONS. NORTHERN
WISCONSIN SHOULD SEE THE LONGEST PERIOD OF SNOW...WITH AROUND AN
INCH OF ACCUMULATION POSSIBLE. FURTHER SOUTH AND EAST...RAIN WILL
MIX WITH SNOW AND ACCUMULATIONS WILL BE LESS THAN A HALF INCH.

PRECIP WILL MOVE OUT TUESDAY MORNING...HOWEVER CONTINUED MVFR TO
IFR CIGS ARE EXPECTED THROUGH THE MORNING.
&&

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

$$

SYNOPSIS.......SKOWRONSKI
SHORT TERM.....ALLEN
LONG TERM......SKOWRONSKI
AVIATION.......ALLEN





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