Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 240913
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
413 AM CDT FRI APR 24 2015

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SYNOPSIS...
ISSUED AT 407 AM CDT FRI APR 24 2015

STILL COOL THE NEXT COUPLE DAYS...THEN SUNNY AND WARMER SUNDAY.

THE FCST AREA WL REMAIN ON THE SW FLANK OF A COMPLEX BLOCKING
PATTERN OVER NERN NOAM AND THE NRN ATLANTIC. TEMPS WL START OUT
BELOW NORMAL...THEN MODERATE BACK CLOSE TO SEASONAL NORMALS BY
EARLY NEXT WEEK. THE BLOCK WL DEFLECT THE BULK OF THE ENERGY WITH
PCPN PRODUCING WX SYSTEMS ARND THE FCST AREA TO THE S. SO
ALTHOUGH SOME LGT PCPN IS POSSIBLE AT TIMES...PCPN AMNTS FOR THE
NEXT 7 DAYS ARE EXPECTED END UP WELL BLO NORMAL.
&&

.SHORT TERM...TODAY...TONIGHT...AND SATURDAY
ISSUED AT 407 AM CDT FRI APR 24 2015

WX SYSTEM FM THE PLAINS WL HEAD TOWARD THE AREA TDA...BEFORE
GETTING DEFLECTED ARND THE AREA TO THE S TOMORROW. AREA OF SHRA
AND SOME TSRA WAS SLOWLY ADVANCING E TOWARD NRN WI THIS MORNING.
NOT A LOT OF PCPN SHOWING UP ON SFC OBS...SO MUCH OF THE PCPN IS
PROBABLY EVAPORATING BEFORE REACHING THE GROUND. THAT AREA OF PCPN
SEEMS TIED TO SOME WK ISENT LIFT AND FRONTOGENETIC FORCING IN RRQ
OF SPEED MAX OVER THE GREAT LAKES RGN. FARTHER S...A SEPARATE AREA
OF PCPN WAS DEVELOPING OVER IA IN RGN OF STRONGER ISENT LIFT AND
AHEAD OF WK MID-LVL SHRTWV. MODELS SHOW BOTH THESE AREAS OF PCPN
MOVG TOWARD THE AREA TDA. THE MAIN QUESTIONS ARE HOW QUICKLY THE
MID-CLDS PRODUCING THE PCPN MV INTO THE AREA...AND WHEN THEY
DO...HOW MUCH PCPN CAN WORK THROUGH THE DRY AIR AND REACH THE
GROUND. 00Z RAOBS FM KGRB/KMPX/KINL WERE IMPRESSIVELY DRY...WITH
NWLY FLOW AT LOW LEVELS. SO THERE WL BE DRY AIR AT LOW-LEVELS TO
EVAPORATE THE INITIAL PCPN. BUT WITH LOW-LEVEL RIDGE SHIFTG ACRS
THE RGN...THE LOW-LEVEL FLOW WL BE WEAK. SO AS PCPN KEEPS FALLING
FM THE MID CLDS...THERE WL BE AN OPPORTUNITY TO ACHIEVE SATURATION
SINCE THERE WL NOT BE A CONTD STG INFLUX OF DRY AIR INTO THE AREA.
THE MOST PERSISTENT FORCING LOOKS TO SET-UP ACRS THE FAR N...SO
THAT AREA WL HAVE THE BEST CHC OF GETTING MEAS PCPN. THE IA PCPN
COULD ALSO WORK INTO THE SW PART OF THE CWA DURING THE LATE AFTN.
THERE IS A RGN FM ABOUT AIG SEWD...HOWEVER...WHERE A MIN IN THE
PCPN CHCS WL EXIST. STRUCTURED FCST WITH LOW CHC POPS NR THE UPPER
MICHIGAN BORDER...AND TRACE EVENT POPS ACRS THE W/SW PART OF THE
AREA. TEMPS WL BE A LITTLE WARMER THAN YDA...BUT INCRG CLDS AND
COOL START TO THE DAY WL TEMPER THE WARMING.

CYCLONE WL STRENGTHEN OVER THE ERN PLAINS TNGT...AS HIGH PRESSURE
BUILDS SEWD ACRS ONTARIO. THAT WL LEAD TO STRENGTHENING ELY FLOW AT
LOW-LEVELS. AT THE SAME TIME...THE FRONTOGENETIC FORCING IN THE
RRQ OF THE UPR SPEED MAX WL WEAKEN AS THE JET SHIFTS E. EXPECT
MID-CLDS TO LINGER OVER THE AREA...BUT PCPN WL DIMINISH AND THE
INFLUX OF FRESH-DRY AIR AT LOW-LEVELS WILL STRENGTHEN. FOR THE
FCST...ALLOWED LOW POPS TO ADVANCE NEWD SOME DURING THE
EVENING...THEN PUSHED THEM BACK FM THE NE LATER IN THE NGT. TEMPS
ALOFT COULD BE COLD ENOUGH FOR SNOW OVER THE N. NOT SURE MUCH PCPN
WL BE LEFT BY THEN...BUT WENT WITH CHC R--/S-- WHERE BOUNDARY
LAYER TEMPS WERE COLD ENOUGH TO SUPPORT SNOW REACHING THE SFC.

THE CYCLONE WL TRACK ESE ACRS IL ON SATURDAY. KEPT CHC POPS ACRS
THE FAR S INTO THE AFTN...THOUGH THE N SHOULD BE FIRMLY UNDER THE
CONTROL OF THE DRY HIGH TO THE NE. CLDS SHOULD DECR FM N-S DURING
THE DAY. WINDS WL CONT TO INCR...AND COULD BE QUITE GUSTY IN ERN
WI LATE IN THE DAY AS THEY COME ARND THROUGH THE 040 DIRECTION
WHICH FAVORS FUNNELING DOWN THE BAY OF GREEN BAY INTO THE FOX
VALLEY. THE CLDS ACRS THE S AND STRENGTHENING ELY WINDS WL KEEP
TEMPS ACRS THE S AND E A FEW DEGREES COOLER THAN TDA.

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY
ISSUED AT 407 AM CDT FRI APR 24 2015

MODELS FORECAST A SHARP MID LEVEL RIDGE OVER THE WESTERN GREAT
LAKES REGION...ALONG WITH SURFACE HIGH PRESSURE...AT THE START OF
THIS PERIOD. NOT THE GREATEST CONSISTENCY AMONG THE MODELS BUT
THE 00Z GFS...00Z ECMWF AND 00Z GEM-NH ALL TRIED TO BRING A
SIGNIFICANT MID LEVEL SHORT WAVE ACROSS THE AREA
TUESDAY/WEDNESDAY. TIMING...SURFACE DETAILS AND QPF FIELDS
DIFFER...LOWERING CONFIDENCE. THE GEM WAS PRETTY MUCH DRY WHILE
THE EC AND GFS BOTH PRODUCED QPF ACROSS PART OF THE FORECAST
AREA. THE GOING FORECAST WAS DRY...SO LEFT IT THAT WAY RATHER
THAN BROAD-BRUSHING BY ADDING A FEW PERIODS OF SLIGHT CHANCE
POPS. THE RETURN OF THE SURFACE RIDGE AND AN APPROACHING MID
LEVEL RIDGE SHOULD KEEP THE REST OF THE LONG TERM DRY AS WELL.

A WARMING TREND IS EXPECTED WITH THIS PATTERN. HIGHS SHOULD BE
NEAR NORMAL FOR THIS TIME OF YEAR BY THE MIDDLE OF NEXT WEEK AND
THEN CLIMB SEVERAL DEGREES ABOVE NORMAL BY THE END OF THE WEEK.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 407 AM CDT FRI APR 24 2015

DRY AIR AT LOW LEVELS SHOULD MAINTAIN FAIRLY GOOD FLIGHT
CONDITIONS /VFR EXPECTED/ THROUGH THE PERIOD DESPITE THE CHC FOR
SOME LGT PCPN THIS AFTN/EVE.
&&

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

$$

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







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