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000
FXUS63 KGRB 122116
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
316 PM CST THU DEC 12 2013

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SYNOPSIS...
ISSUED AT 316 PM CST THU DEC 12 2013

A COLD PERIOD WITH SOME LIGHT SNOW AT TIMES.

OVERALL HIGH UPR HEIGHTS IN THE ERN PAC WL FAVOR THE CONTINUED
GENERATION OF FRIGID AIR ACRS MUCH OF CANADA. ACRS NOAM...UPR
TROF POSN WL REMAIN IN THE E FOR MOST OF THE PERIOD...THEN IS
LIKELY TO BEGIN A TRANSITION BACK TO THE W LATE IN THE PERIOD AS
RIDGING SHARPENS OFF THE WEST COAST. ALTHOUGH COLD AIR WILL
CONTINUE TO DOMINATE CANADA...THERE WL PROBABLY BE A COUPLE DAYS
WERE SOME MODIFIED PAC AIR IS ABLE TO BREAK THROUGH ACRS THE CONUS
BETWEEN THE ARCTIC SURGES. SO TEMPS WL START OUT WELL BLO
NORMAL...MODERATE BACK CLOSE TO NORMAL FOR A COUPLE DAYS NEXT
WK...THEN DROP OFF AGAIN LATE IN THE PERIOD.

THE FAST UPR FLOW WL BRING NUMEROUS DISTURBANCES EWD IN THE STG
BAROCLINIC ZONE ACRS THE RGN. THAT COMBINED WITH A FAVORABLE
TRAJECTORY FOR LAKE-EFFECT AT TIMES WL LEAD TO SEVERAL ROUNDS OF
LGT SNOW. BUT MOISTURE WL BE LIMITED...PCPN AMNTS WL MOST LIKELY
END UP BLO NORMAL FOR THE PERIOD.
&&

.SHORT TERM...TONIGHT AND FRIDAY
ISSUED AT 316 PM CST THU DEC 12 2013

SKIES BASICALLY CLR ACRS THE AREA EARLY THIS AFTN...BUT THE NEXT
BATCH OF CLDS WAS RACING IN FM THE W. MODELS HINT AT LGT QPF ACRS
MAINLY THE N TNGT. THINK THIS WL BE ANOTHER ONE OF THOSE SITNS
LIKE LAST NGT WHERE WE GET A FAIRLY LARGE AREA OF S-...BUT WITH
ONLY MINOR ACCUMS. BASED ON INCRG RETURNS ON THE RADAR MOSAIC...
BROUGHT THE CHC OF SN ACRS THE N FAIRLY QUICKLY THIS EVENING...
THEN TOOK POPS UP TO LIKELY ACRS THE N OVERNIGHT. TEMPS PROBABLY
WON/T FALL TOO FAR WITH PRETTY SOLID LOOKING MID CLD DECK
OVERSPREADING THE AREA ARND SUNSET. USED BLEND OF GUID TO CREATE 3
HOURLY TEMP GRIDS...THEN TOOK MIN FROM THOSE.

OCNL LGT SNOW AND FLURRIES WL LIKELY CONT FRI MORNING. THEN MAIN
CONCERN SHIFTS TO THE POTENTIAL FOR LAKE-EFFECT DEVELOPING OVER E-
C WI AS WINDS SHIFT TO THE NE. AIR/LK SFC TEMP DIFFERENCE FAIRLY
SIG. PREV FCST SEEMED TO HAVE SITN HANDLED PRETTY WELL WITH
LIKELY POPS IN THE AFTN...AND A GENERAL SNOWFALL OF 1/2 TO 1 INCH
IN THE LAKESIDE COUNTIES. THAT/S A GOOD STARTING POINT...THOUGH
NEED TO KEEP A CLOSE WATCH FOR ANY ORGANIZED SNOW BANDS COMING
INLAND. ONE OF THOSE COULD EASILY DROP A FEW INCHES OF SNOW OVER A
SMALL AREA DURING THE AFTN.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY
ISSUED AT 316 PM CST THU DEC 12 2013

STILL SOME DIFFERENCES NOTED AMONG MODELS REGARDING THE SYSTEM
THAT WILL IMPACT THE AREA FRIDAY NIGHT INTO SATURDAY. MODELS KEPT
THE HIGHEST QPF/SNOWFALL TOTALS TO THE SOUTH OF THE FORECAST AREA
AS THE INVERTED TROUGH PASSES ACROSS THE WESTERN GREAT LAKES
REGION. HPC GUIDANCE BROUGHT AROUND 2 INCHES OF SNOW TO SOUTHEAST
MANITOWOC COUNTY...BUT THAT TOTAL SEEMS RATHER LOW CONSIDERING THE
FAVORABLE FETCH OVER LAKE MICHIGAN FRIDAY NIGHT ALONG WITH SOME
UPPER LEVEL DIVERGENCE ASSOCIATED WITH A COUPLED JET STRUCTURE AT
250MB. EVEN WHEN WINDS SHIFT TO SOUTHEAST THE AIR MASS SHOULD STILL
BE COLD ENOUGH FOR LAKE ENHANCEMENT/EFFECT AS THE SYSTEM DEPARTS.
HAVE GONE WITH TOTALS MAINLY IN THE 3 TO 5 INCH RANGE IN THE
LAKE SHORE COUNTIES FOR FRIDAY NIGHT THROUGH SATURDAY. TOTALS IN
THAT RANGE ARE SHORT OF ADVISORY CRITERIA...BUT IF A BAND OF LAKE
EFFECT SNOW DOES DEVELOP...LOCALLY HEAVIER AMOUNTS CAN BE
EXPECTED.

THERE DOES NOT APPEAR TO BE A REAL BREAK IN THE ACTION BETWEEN THE
SOUTHERN BRANCH SYSTEM AND SNOWFALL ASSOCIATED WITH A SHORT WAVE
IN THE NORTHERN BRANCH AT MID LEVELS. A DEVELOPING SURFACE LOW
SHOULD PASS JUST NORTH OF WISCONSIN SATURDAY NIGHT. AS A
RESULT...A CHANCE FOR SNOW HAS BEEN CONTINUED THROUGH SATURDAY
NIGHT...WITH SOME LAKE EFFECT POSSIBLE IN FAR NORTH CENTRAL
WISCONSIN AND DOOR COUNTY ON SUNDAY BEHIND THIS FEATURE AS IT
DEPARTS.

UPPER LEVEL FLOW GRADUALLY SHIFTS TO A MORE ZONAL PATTERN DURING
THE LATTER HALF OF NEXT WEEK. UNTIL THEN...CLIPPER SYSTEMS REMAIN
AN ISSUE AND AT OR BELOW NORMAL TEMPERATURES WILL PERSIST WHILE
THE NORTHWEST FLOW CONTINUES.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1131 AM CST THU DEC 12 2013

LOOKS LIKE ANOTHER ROUND OF LIGHT SNOW LATE TNGT...THIS TIME MORE
ACRS THE N. IT DOESN/T TAKE MUCH FORCING/SNOW TO GET VSBYS TO COME
DOWN SIG IN THE COLD AIR MASS ACRS THE RGN...AS MANY SITES WERE
AOB 2SM THIS MORNING. SO WENT WITH LOWER-END MVFR AND SOME IFR
VSBYS IN THE TAFS.
&&

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

$$

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