Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 280754
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
254 AM CDT TUE APR 28 2015

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND WEDNESDAY
ISSUED AT 254 AM CDT TUE APR 28 2015

AS HIGH PRESSURE DRIFTS EAST OF THE AREA TODAY...A WEAKENING FRONTAL
BOUNDARY WILL DROP INTO THE NORTHWEST HALF OF THE STATE THIS
AFTERNOON AND EVENING. EARLY THIS MORNING...RADARS TO THE
NORTHWEST SHOW LIGHT SHOWERS OVER NORTHWEST MINNESOTA AND EASTERN
NORTH DAKOTA AND SLOWLY MOVING EASTWARD. ALL MODELS ARE CONSISTENT
WITH WASHING OUT THIS FRONTAL BOUNDARY AND SHOWERS BEFORE REACHING
NORTH CENTRAL WISCONSIN THIS AFTERNOON AND EVENING. LIKELY ONLY
PATCHY MID LEVEL CLOUDS PASSING OVER THIS EVENING.

PRIMARY ISSUE DURING THIS PERIOD CENTERS ON THE SHARP HEIGHT FALLS
ON WEDNESDAY AS A THE CENTER OF A COLD UPPER LOW SYSTEM DROPS
SOUTHWARD OVER EASTERN WISCONSIN. SURFACE DEW POINTS ONLY IN THE
30S ON WEDNESDAY AND CAA ALREADY ONGOING AS THIS COLD CORE TRACKS
OVER. ADDED SMALL CHANCE OF SHOWERS IN THE AFTERNOON FOR THIS
FEATURE AND DID ADD A SMALL AFTERNOON MENTION OF TSRA WITH
FORECAST SOUNDINGS OF EACH THE NAM AND GFS SHOWING STEEP LAPSE
RATES AND TOTAL TOTALS IN THE 50 TO 56 RANGE. CONFIDENCE OF A
TSRA LOW DUE TO THE RELATIVELY DRY AIR MASS BUT HARD TO IGNORE
THIS INSTABILITY...COMPACT LOW WITH VORT FIELD...ALONG WITH SOME
SOME POTENTIAL OF MID LEVEL MOISTURE POOLING WITH THE LOW CENTER.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
ISSUED AT 254 AM CDT TUE APR 28 2015

SOMEWHAT OF AN AMPLIFIED FLOW AT MID-WEEK WITH A CLOSED UPR LOW
MOVING ACROSS THE ERN CONUS INTO THE WRN ATLANTIC AND A WEAKENING
UPR RDG OVER THE CNTRL CONUS. BY THE START OF THE WEEKEND...THE
MEAN FLOW IS ESSENTIALLY ZONAL ACROSS THE CONUS. THIS TRANSLATES
TO A FASTER SERIES OF SYSTEM/FRONTAL BOUNDARIES...BUT A LACK OF
MOISTURE WOULD LIMIT PCPN COVERAGE. A BETTER CHC OF PCPN MAY
ARRIVE LATE SUNDAY INTO MON AS A NRN STREAM SHORTWAVE TROF MOVES
ACROSS THE NRN TIER OF STATES. INITIALLY...TEMPS TO BE SLIGHTLY
BELOW NORMAL...HOWEVER AS THE MEAN FLOW FLATTENS...TEMPS WL RISE
TO ABOVE NORMAL LEVELS.

MODELS ARE STILL STRUGGLING WITH THE LOCATION OF THE CLOSED UPR
LOW WED NGT. NAM IS FARTHEST WEST BY TAKING THE UPR LOW SWD THRU
ERN WI. THE GFS IS FARTHEST EAST BY TAKING THE UPR LOW SWD THRU
CNTRL LWR MI. EVEN IF THE NAM ENDS UP BEING CORRECT...THE LOSS OF
DAYTIME HEATING WOULD HELP STABILIZE THE ATMOSPHERE AND LIMIT ANY
PCPN CHCS. AFTER COLLABORATING WITH MKX AND ARX...HAVE DECIDED TO
ADD A SMALL POP TO CNTRL/E-CNTRL WI WED EVENING. MIN TEMPS ARE NO
BARGAIN EITHER DEPENDING ON WHICH MODEL IS CORRECT AS CLOUD COVER
MAY RANGE FROM PARTLY CLOUDY TO CLEAR. FOR NOW...HAVE USED A BLEND
WHICH BRINGS TEMPS DOWN INTO THE LWR 30S NORTH...UPR 30S SOUTH.

THE UPR LOW CONTS TO DROP S-SE AWAY FROM THE GREAT LAKES REGION ON
THU AND WL BE REPLACED BY A WEAK SFC RDG PUSHING INTO WI. WHILE
SKIES ARE EXPECTED TO BE MOSTLY SUNNY...A N-NE WIND WL KEEP ERN WI
COOLER THAN THEIR CNTRL WI COUNTERPARTS. LOOK FOR MAX TEMPS TO
RANGE FROM THE LWR 50S NEAR LAKE MI TO THE LWR TO MID 60S ACROSS
CNTRL WI.

QUIET WEATHER TO PREVAIL THRU THU NGT AS THE SFC RDG OVER THE
GREAT LAKES IS JOINED BY A WEAKENING UPR RDG FROM THE CNTRL PLAINS
TO THE WRN GREAT LAKES. MOSTLY CLEAR SKIES WITH LIGHT WINDS SHOULD
BRING A COOL NGT TO NE WI WITH MIN TEMPS RANGING FROM THE LWR TO
MID 30S NORTH...MID TO UPR 30S SOUTH. ATTENTION TURNS TO THE UPR
MS VALLEY WHERE A WEAK SHORTWAVE TROF/WEAK CDFNT ARE PROGGED TO BE
SITUATED ON FRI. LIFT...FORCING AND MOISTURE ALL APPEAR TO BE
LACKING AND THE 00Z MODEL OUTPUT ALL SHOW A WEAKENING TREND
OVERALL WITH THIS SYSTEM. MAY KEEP A TOKEN MINIMAL POP ACROSS
CNTRL WI AS THE SYSTEM APPROACHES...BUT ANY WIDESPREAD PCPN
APPEARS DOUBTFUL AT THIS POINT. A RETURN TO A SW WIND WL HELP
PROVIDE A BOOST TO TEMPS WITH READINGS REACHING THE MID 50S NEAR
LAKE MI...BUT MID TO UPR 60S FOR INLAND LOCATIONS.

THIS WEAKENING SYSTEM TO MOVE THRU WI FRI NGT AND MAY BRING AN
ISOLATED SHWR/SPRINKLES SOMEWHERE OVER THE FCST AREA. MORE CLOUDS
FRI NGT WL LEAD TO MILDER CONDITIONS WITH MIN TEMPS ONLY DROPPING
INTO THE 40S. THE GFS HAS THROWN A WRENCH INTO SAT`S FCST BY
SENDING A SECONDARY SFC TROF TOWARD THE WRN GREAT LAKES TO
INTERACT WITH INCREASING INSTABILITY OVER WI. THE GEM DOES NOT
SHOW THIS SFC TROF...THUS NO LIFTING MECHANISM FOR PCPN. DO NOT
WANT TO COMPLETELY DISMISS THE GFS AS THE MEAN FLOW FLATTENS AND
THE TIMING OF WEATHER SYSTEMS BECOMES PROBLEMATIC. HAVE PLACED A
SMALL POP OVER NE WI FOR NOW. SAT SHOULD BE A WARM DAY EITHER WAY
WITH MAX TEMPS IN THE LWR 60S NEAR LAKE MI...LWR TO MID 70S CNTRL
WI.

A BETTER CHC FOR PCPN ARRIVES LATE SUNDAY THRU SUNDAY NGT AS A
SHORTWAVE TROF PUSHES ACROSS THE NRN TIER OF STATES AND IS
ACCOMPANIED BY A MORE ROBUST CDFNT. IF ENUF GULF MOISTURE CAN GET
PULLED NORTH BEFORE THE CDFNT ARRIVES...A GOOD SOAKING RAIN WOULD
OCCUR...ESPECIALLY IF THE UPR JET CAN GET ALIGNED PROPERLY. FAIRLY
HI CHC POPS IN PLACE DESPITE BEING DAY 6 INTO DAY 7. GRADUAL
IMPROVING CONDITIONS EXPECTED ON MON AS THIS SYSTEM PULLS AWAY.
TEMPS WL REMAIN ABOVE NORMAL FOR BOTH SUNDAY AND MON.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1057 PM CDT MON APR 27 2015

CLEAR SKIES AND LIGHT WINDS SHOULD ALLOW FOR NICE
FLYING WEATHER TONIGHT THROUGH TUESDAY.
&&

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

$$

SHORT TERM.....TDH
LONG TERM......KALLAS
AVIATION.......RDM





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