Area Forecast Discussion
Issued by NWS Green Bay, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KGRB 211614
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1114 AM CDT TUE APR 21 2015

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 353 AM CDT TUE APR 21 2015

CLOUDY AND CHILLY WITH RAIN AND SNOW SHOWERS THROUGH TOMORROW.
RELATIVELY TRANQUIL FOR THE REST OF THE WORK WEEK AND THE UPCOMING
WEEKEND...BUT WITH CONTINUED BELOW NORMAL TEMPERATURES.

LARGE SCALE PATTERN ACRS NOAM IS HIGHLY AMPLIFIED...WITH A SHARP
FULL-LATITUDE RIDGE JUST INLAND FM THE WEST COAST...AND A DEEP
TROF OVER THE GREAT LAKES RGN. THE PATTERN IS EXPECTED TO EVOLVE
INTO A BLOCKING REGIME AS STG POSITIVE UPR HEIGHT ANOMALY BUILDS
WWD FM THE NORTH ATLANTIC...SETTLING IN N OF NEGATIVE ANOMALY
WITH THE GREAT LAKES UPR TROF. THOUGH IT MAY MORPH IT/S STRUCTURE
SOME OVER TIME...ONCE IN PLACE...THE BLOCK IS EXPECTED TO PERSIST
THROUGH THE REST OF THE FCST PERIOD...AND PROBABLY BEYOND.

GETTING LOCKED IN NR THE NEGATIVE ANOMALY OF A BLOCK GENERALLY
RESULTS IN BELOW NORMAL TEMPERATURES...AND THIS CASE WILL BE NO
DIFFERENT. THE COLDEST DAYTIME TEMPERATURES WILL OCCUR THE NEXT
COUPLE DAYS WHILE THERE ARE CLOUDS AND PRECIPITATION.
CONSIDERABLY BELOW NORMAL TEMPERATURES WILL PERSIST FOR THE REST
OF THE WORK WEEK. SOME MODERATION IS LIKELY DURING THE WEEKEND.
DESPITE THE SCT SHOWERS THE NEXT COUPLE DAYS...PCPN AMNTS ARE
LIKELY TO END UP BELOW NORMAL FOR THE PERIOD.
&&

.SHORT TERM...TODAY...TONIGHT...AND WEDNESDAY
ISSUED AT 353 AM CDT TUE APR 21 2015

COLD CYCLONIC UPR FLOW WL DOMINATE THE SHORT-TERM PERIOD. THAT
WILL LEAD TO SCATTERED TO NUMEROUS SHOWERS...A LOT OF WHICH WILL
FALL AS SNOW. TRAJECTORIES TURN NLY ENOUGH AND AIR/WATER
TEMPERATURE DIFFERENCES INCREASE TO THE POINT WHERE SOME LAKE-
EFFECT IS ALSO LIKELY IN THE LAKE SUPERIOR SNOWBELT OVERNIGHT.
ADDITIONAL SHRTWV ENERGY WL LIKELY BE DROPPING SWD AT THAT TIME.
THE COMBINATION OF FACTORS WL LIKELY RESULT IN AN INCH OR TWO OF
SNOW IN THE SNOWBELT.

OTHERWISE...BUILT TEMP GRIDS FROM A BLEND OF THE TOP-PERFORMING
GUIDANCE PRODUCTS. PRECIPITATION TYPE WL PRETTY MUCH COME DOWN TO
BOUNDARY LAYER TEMPERATURES...AS TEMPS ALOFT WL BE COLD ENOUGH
FOR SNOW THROUGHOUT. SO GENERATED PRECIP TYPE IN WX GRIDS USING
HOURLY TEMPS.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
ISSUED AT 353 AM CDT TUE APR 21 2015

A MID LEVEL CYCLONE ACROSS EASTERN NOAM WILL KEEP THE AREA IN
NORTHWEST FLOW FOR AT LEAST THE REST OF THE WORK WEEK. THE FLOW
IS FORECAST TO BECOME MORE ZONAL OVER THE WEEKEND AS A RIDGE
MOVES INTO THE REGION FROM THE WEST. ANOTHER TROUGH IS EXPECTED TO
QUICKLY FOLLOW THE RIDGE...BUT MODELS WERE SHOWING SIGNIFICANT
DIFFERENCES IN ITS STRENGTH AND TIMING.

COLD AIR IN NORTHWEST FLOW OVER THE WARMER WATERS OF LAKE SUPERIOR
WILL BRING A CHANCE FOR SNOW SHOWERS ACROSS MAINLY NORTH CENTRAL
WISCONSIN INTO THURSDAY MORNING BEFORE WINDS BECOME UNFAVORABLE
FOR LAKE EFFECT IN THE FORECAST AREA. PRECIPITATION CHANCES FOR
THE REST OF THE FORECAST PERIOD ARE LOW DUE TO MODEL DIFFERENCES
IN TIMING AND STRENGTH OF SYSTEMS.

HIGH TEMPERATURES ARE EXPECTED TO BE ABOUT 5 TO 10 DEGREES BELOW
NORMAL FOR THIS TIME OF YEAR. THE WARMEST DAYS SHOULD BE SUNDAY
AND MONDAY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1102 AM CDT TUE APR 21 2015

LOW-END VFR TO MVFR CONDITIONS EXPECTED IN CENTRAL AND EASTERN
WISCONSIN THROUGH TONIGHT AS AN UPPER LEVEL DISTURBANCE BRINGS
CLOUDS AND SCATTERED SHOWERS TO THE AREA. SHOWERS SHOULD DIMINISH
AFTER SUNSET. FURTHER NORTH...SNOW SHOWERS AND MVFR CONDITIONS WILL
PREVAIL TODAY AND OVERNIGHT.

MORE CLOUDS ARE EXPECTED WEDNESDAY WITH MVFR CONDITIONS LIKELY.
SHOWERY ACTIVITY SHOULD BE LESS WIDESPREAD FOR MOST OF NORTHEAST
WISCONSIN...EXCEPT IN NORTHERN WISCONSIN WHERE SNOW SHOULD
CONTINUE INTO AT LEAST THE AFTERNOON.

GUSTY WEST WINDS WILL SUBSIDE TONIGHT BEFORE INCREASING AGAIN
WEDNESDAY.

&&

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

$$

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






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.