Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 271712
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1212 PM CDT WED MAY 27 2015

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 410 AM CDT WED MAY 27 2015

SCATTERED SHOWERS TODAY...THEN QUITE WARM THURSDAY.

THE MAIN WESTERLIES ARE ACRS CANADA...WITH A WEAKER BUT ENERGETIC
SRN STREAM ACRS THE CONUS. WITHIN THE SRN STREAM...THE MEAN TROF
POSN IS OVER THE CENTRAL STATES...WITH A RIDGE NEAR THE EAST
COAST. THE DEGREE OF SEPARATION OF THE STREAMS WL TEMPORARILY
DECREASE DURING THE FIRST HALF OF THE FCST PERIOD AS STG NRN
STREAM SHRTWV SWINGS THROUGH SRN CANADA...AND DRAWS IN SOME SRN
STREAM ENERGY. BUT THE SPLIT IS EXPECTED TO RE-EMERGE NEXT
WK...WITH SRN STREAM UPR TROF POSN NR THE WEST COAST AND BROAD
RIDGING OVER THE CENTRAL AND ERN CONUS.

THESE ARE PRETTY TYPICAL EARLY SUMMERTIME WX PATTERNS.
TEMPERATURES WL START OUT ABV NORMAL...FALL TO BELOW NORMAL
LEVELS FOR THE WEEKEND AS THE NRN STREAM SHRTWV PROGRESSING ACRS
CANADA DRAWS A COOL ANTICYCLONE SEWD INTO GREAT LAKES RGN FM NWRN
CANADA...THEN WARM BACK TO AOA NORMAL FOR NEXT WEEK. THERE WL BE
NUMEROUS OPPORTUNITIES FOR PCPN DURING THE PERIOD...AND THE
PROXIMITY OF THE SRN STREAM WL PROVIDE AMPLE MOISTURE...SO AMNTS
ARE LIKELY TO END UP ABV NORMAL FOR THE PERIOD.
&&

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 410 AM CDT WED MAY 27 2015

UPR SHRTWV RESPONSIBLE FOR THE WET WX OF THE PAST 24 HRS WAS
BEGINNING TO EXIT THE REGION. LINGERING PCPN IN UPR DEFORMATION
ZONE WL WRAP BACK THROUGH THE AREA THIS MORNING. BUT RADAR MOSAIC
SHOWING DECR RETURNS...SO THE VERY EFFICIENT PCPN PRODUCING
CONVECTION WL DIMINISH BACK TO JUST SCT SHOWERS. WK SHRTWV
DROPPING SE ACRS THE AREA THIS AFTN SHOULD COMBINE WITH LINGERING
INSTABILITY TO PRODUCE SCT SHRA/TSRA THIS AFTN. THE BEST CHC WL BE
OVER THE N...WHICH WL ALSO BE CLOSE TO WK FRONTAL BOUNDARY
DROPPING SWD INTO UPPER MICHIGAN. SO PLACED HIGHEST POPS IN THE N.
WLY FLOW TDA SHOULD DRIVE THE MILD AIR RIGHT TO THE LAKESHORE.
USED BLEND OF GUIDANCE PRODUCTS FOR MAX TEMPS...BUT ADJUSTED TEMPS
LAKESIDE UP SOME.

SHOWERS WL PROBABLY LINGER INTO THE EVENING BEFORE ENDING...THEN
SKIES SHOULD CLR. GIVEN THE WK PRESSURE GRADIENT ACRS THE
AREA...WINDS WL BE LGT. AFTER ALL THE RAIN OF THE PAST 24 HRS...
HARD TO BELIEVE THERE WON/T BE SOME FOG...ESPECIALLY IN LOW-LYING
AREAS AND NR RIVERS/STREAMS. MOS GUIDANCE PRODUCTS ONLY HINT AT
THIS...BUT THOUGHT IT DESERVED BEING ADDED TO THE GRIDS.

THE AFOREMENTIONED WK BOUNDARY MAY SAG INTO NRN WI BY EARLY
THU...THEN SHOULD LIFT BACK NWD AS FLOW ALOFT BEGINS TO BACK. THAT
WL ALLOW VERY WARM AIR TO OVERSPREAD THE AREA. WENT WITH BLEND OF
BIAS-CORRECTED PRODUCTS FOR MAXES...WHICH RESULTED IN BUMPING
MAXES UP A COUPLE DEGREES MOST AREA. THE ONE AREA THAT WL BE
COOLER IS THE LAKESHORE...AS GRADIENT SSELY FLOW WL BRING COOLER
AIR INLAND. SOME DESTABILIZATION WL OCCUR DURING THE DAY...WITH
MUCAPES OFF THE NAM IN THE 1.5-2K J/KG RANGE BY MID-LATE AFTN.
ALTHOUGH THAT IS PROBABLY TOO HIGH AS DWPTS MAY MIX OUT
SOME...THERE WL BE ENOUGH INSTABILITY FOR SHRA/TSRA. BUT LARGE
SCALE FORCING WL BE LACKING AS UPR RIDGING STRENGTHENS OVER THE
AREA. THE MOST LIKELY LOCATION FOR DEVELOPMENT WL BE N OF THE
AREA...BUT CARRIED CHC POPS INTO FAR NRN WI DUE TO THE PROXIMITY
OF THE FRONT.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 410 AM CDT WED MAY 27 2015

MAIN FCST FOCUS REMAINS THE ADDITIONAL PCPN POTENTIAL FROM THU NGT
THRU FRI NGT AS A SYSTEM WORKS ACROSS THE REGION. WHILE THE THREAT
OF SEVERE WEATHER ON FRI CANNOT BE RULED OUT...LOCALLY HEAVY
RAINFALL REMAINS THE PRIMARY THREAT DURING THIS TIME PERIOD. A
MORE TRANQUIL AND COOLER PATTERN TO THEN ARRIVE FOR THE WEEKEND
BEFORE TEMPS RETURN CLOSER TO NORMAL EARLY NEXT WEEK.

CLOUDS ARE EXPECTED TO BE ON THE INCREASE OVER NE WI THU EVENING
AS A CDFNT MOVES ACROSS THE UPR MS VALLEY AND A TRAILING SHORTWAVE
TROF PUSHES THRU THE NRN/CNTRL PLAINS. AHEAD OF THESE FEATURES...
A PREVAILING S-SW FLOW INTO WI WL CONT TO USHER WARM/MOIST AIR
INTO THE GREAT LAKES WITH WAA AND A SHORTWAVE COMBINING TO BRING A
DECENT CHC OF SHWRS BACK TO THE AREA AFTER MIDNGT. A MILD NGT IS
ON TAP AS MIN TEMPS TO ONLY DROP INTO THE MID 50S NEAR LAKE MI/
BAY OF GREEN BAY...AROUND 60 DEGS ELSEWHERE.

FRI IS STILL LOOKING LIKE A WET AND POSSIBLY STORMY DAY ACROSS THE
REGION AS THE EWD MOVING CDFNT SLAMS INTO A WARM/UNSTABLE AIR MASS
OVER WI. PLENTY OF INSTABILITY TO BE IN PLACE WITH CAPES RISING TO
AROUND 1500 J/KG...LI`S DROP AS LOW AS -5 AND MID-LEVEL LAPSE
RATES ARE FAIRLY STEEP AT 6.5 C/KM. BESIDES THE FNT...THERE WL BE
ADDITIONAL LIFT PROVIDED BY THE RIGHT ENTRANCE REGION OF THE UPR
JET. SHEAR THO IS RATHER WEAK AND THERE WL BE CONSIDERABLE CLOUD
COVER OVERHEAD THAT WOULE LIMIT THE INSTABILITY. UNLESS WE CAN GET
SOME KIND OF BRIEF CLEARING (DOUBTFUL)...THE MAIN WORRY ON FRI
WOULD BE HEAVY RAINFALL WITH DEW POINTS IN THE UPR 50S TO LWR 60S
AND PW VALUES IN THE 1.5 TO 1.75 INCH RANGE (+2 STANDARD DEVIATION
FROM NORMAL). MAX TEMPS WL OBVIOUSLY BE IMPACTED BY THE PCPN WITH
READINGS RANGING FROM AROUND 70 DEGS N-CNTRL/LAKESHORE...UPR 70S
ACROSS E-CNTRL WI.

THE MAIN QUESTION HEADED INTO FRI NGT IS WHETHER A SFC WAVE WL
DEVELOP/MOVE ALONG THE CDFNT AND HOLD PCPN ACROSS THE BULK OF WI
THRU THE NGT. EVEN IF A SFC WAVE DOES NOT DEVELOP...THE WEAKENING
SHOFTWAVE TROF WOULD BE ENUF TO GENERATE ADDITIONAL SHWRS/TSTMS
ACROSS THE FCST AREA. MODELS HAVE BEEN INCONSISTENT WITH EITHER OF
THESE SOLUTIONS...SO HAVE FOCUSED HIGHER POPS FOR FRI EVENING AND
THEN BEGIN TO TAPER POPS DOWN ESPECIALLY ACROSS THE NORTH WHERE
DRIER AIR WL START TO ADVECT INTO WI ON NORTH WINDS. A PRETTY GOOD
BURST OF CAA IS SHOWN BY THE MODELS WHICH WOULD SEND MIN TEMPS
DOWN INTO THE 40-45 DEG RANGE NORTH...45-50 DEG RANGE SOUTH. ANY
SMALL LINGERING PCPN CHC OVER E-CNTRL WI WL END EARLY SAT MORNING
AS A LARGE CANADIAN AREA OF HI PRES MOVES ACROSS ONTARIO AND FEEDS
DRIER AIR INTO WI ON BRISK NE WINDS. EVEN WITH THE RETURN OF
SUNSHINE BY SAT AFTERNOON...PREVAILING CAA WL LIMIT MAX TEMPS TO
ONLY TO THE MID 50S FAR NORTH AND ALONG LAKE MI...AROUND 60 DEGS
CNTRL/E-CNTRL WI.

THE HI PRES IS FCST TO SETTLE SOUTH INTO THE GREAT LAKES FOR THE
LATTER HALF OF THE WEEKEND AND KEEP THE COOL/QUIET WEATHER INTACT.
SAT NGT CONTS TO LOOK DOWNRIGHT CHILLY WITH POTENTIAL FROST
HEADLINES FOR AT LEAST NRN WI AS TEMPS DIP INTO THE 30S. SUNDAY
APPEARS TO BE A FEW DEGS WARMER THAN SAT AS WINDS VEER MORE EAST
THAN NE. THIS WOULD PLACE MAX TEMPS IN THE UPR 50S NEAR LAKE MI...
60-65 DEG RANGE ELSEWHERE. EVEN THO THE SFC HI LW SHIFT EAST
TOWARD THE CANADIAN MARITIMES/NE CONUS BY THE START OF THE WORK
WEEK...NE WI TO STILL BE ON THE WRN PERIPHERY OF THE SFC HI SO
EXPECT A CONTINUATION OF DRY WEATHER WITH GRADUALLY MODERATING
TEMPS AS 8H TEMPS RISE TO GREATER THAN +10C. THIS WOULD ALLOW FOR
MAX TEMPS ON MON TO REACH NEAR NORMAL FOR THE FIRST DAY OF JUNE
(UPR 60S TO LWR 70S...BUT COOLER LAKESIDE).

BY THE END OF THE FCST PERIOD...THE ATMOSPHERE APPEARS TO BE IN
THE PROCESS OF RELOADING AS A NEW UPR TROF TO BE LOCATED OVER THE
WRN CONUS...A W-SW MEAN FLOW TO DEVELOP OVER THE CNTRL CONUS AND A
CDFNT TO BE DRAPED FROM THE NRN PLAINS E-NE TO ROUGHLY LAKE
SUPERIOR. THE EXACT LOCATION OF THIS FRONTAL BOUNDARY WL
EVENTUALLY DETERMINE PCPN CHCS...MAINLY FOR NRN WI MON NGT INTO
TUE. HAVE FOLLOWED MODEL CONSENSUS WHICH IMPINGES SMALL POPS
TOWARD NRN WI. MAX TEMPS WL CONT TO SLOWLY WARM WITH READINGS BY
TUE REACHING THE LWR TO MID 70S (60S NEAR THE BAY AND LAKE).
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1211 PM CDT WED MAY 27 2015

LIGHT RAIN SHOWERS WILL EXIT NORTHEAST WISCONSIN EARLY
THIS AFTERNOON...WHICH WILL RETURN ANY LINGERING MVFR CIGS/VSBYS
BACK TO VFR.  CLOUDS WILL BUILD AGAIN MID TO LATE AFTERNOON ACROSS
NORTHERN WISCONSIN WHERE SHOWERS AND A FEW THUNDERSTORMS ARE
EXPECTED TO DEVELOP.  EXPECTED COVERAGE TO BE A LITTLE TOO SPARSE TO
MENTION AT RHI EXPLICITLY.  COVERAGE WILL DIMINISH THIS
EVENING...BUT THE RECENT RAINFALL AND LIGHT WINDS WILL FAVOR FOG
DEVELOPMENT LATE TONIGHT.
&&

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

$$

SYNOPSIS.......SKOWRONSKI
SHORT TERM.....SKOWRONSKI
LONG TERM......KALLAS
AVIATION.......MPC



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