Area Forecast Discussion
Issued by NWS Green Bay, WI

Home | Current Version | Previous Version | Graphics & Text | 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 210923
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
423 AM CDT MON JUL 21 2014

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SYNOPSIS...
ISSUED AT 409 AM CDT MON JUL 21 2014

VERY WARM AND HUMID THE NEXT COUPLE DAYS...WITH A CHANCE OF
THUNDERSTORMS TONIGHT THROUGH TUESDAY EVENING.

SUBTROPICAL DOMINATING MUCH OF THE CONUS AT THE START OF THE FCST
PERIOD...WITH UPR ANITCYCLONES CENTERED OVER THE DESERT SW AND THE
WRN ATL. A WEAKNESS IN THE RIDGE EXISTS OVER THE ERN CONUS. THE
MAIN BELT OF WESTERLIES WL SAG SWD A BIT THE NEXT COUPLE DAYS AS
SHRTWV CROSSES SRN CANADA AND AMPLIFIES INTO THE ERN NOAM WEAKENSS
IN THE RIDGE. THE PATTERN WL FLATTEN AGAIN LATE IN THE WEEK AND
DURING THE WEEKEND AS A STRONGER SHRTWV MIGRATES EWD ACRS SRN
CANADA AND THE FAR NRN CONUS. THAT FEATURE IS EXPECTED TO
INITIATE A MAJOR AMPLIFICATION OF THE LNGWV PATTERN WHEN IT
REACHES THE ERN CONUS LATE NEXT WEEKEND. THE RESULT WL BE A RATHER
BLOCKY PATTERN WITH A MODESTLY DEEP TROF CENTERED NR THE LOWER
GREAT LAKES...S OF A POSITIVE HEIGHT ANOMALY NR HUDSON BAY. THAT
PATTERN LOOKS VERY STABLE...AND SEEMS LIKELY TO PERSIST MUCH OF
THE FOLLOWING WEEK.

A COUPLE VERY WARM/HUMID DAYS ARE EXPECTED AT THE START OF THE
FCST PERIOD...THEN HUMIDITIES WL DROP AND TEMPERATURES WL SETTLE
BACK CLOSE TO SEASONAL NORMALS FOR THE REST OF THE PERIOD. A
RETURN TO BLO NORMAL TEMPS SEEMS LIKELY BEYOND THE END OF THE FCST
PERIOD. THE MAIN OPPORTUNITIES FOR PCPN WL BE LATE TNGT INTO TUE
EVENING AS COLD FRONT SAGS SWD INTO THE MOIST UNSTABLE AIR ACRS
THE AREA...AND AGAIN DURING THE UPCOMING WEEKEND AS UPR SHRTWV
CROSSING THE NRN CONUS AND SRN CANADA ARRIVES IN THE AREA.
&&

.SHORT TERM...TODAY...TONIGHT...AND TUESDAY
ISSUED AT 409 AM CDT MON JUL 21 2014

AS WAS THE CASE THE PAST SEVERAL MORNINGS...PATCH OF CLDS FM THE
W WL EDGE INTO THE FCST AREA EARLY THIS MORNING. EXPECT THE CLDS
TO DISSIPATE AFTER SUNRISE AND BE REPLACED BY SOME CU.

THE MAIN FCST ISSUE IS FIGURING OUT THE EVOLUTION OF CONVECTION
AND IT/S IMPACT ON THE OTHER SENSIBLE WX ELEMENTS. MODELS PRETTY
MUCH AGREE ON CONVECTION FIRING OVER THE NRN PLAINS THIS AFTN...
THEN GROWING UPSCALE INTO A SVR MCS AND TRACKING EWD AND INTO FAR
NW WI/WRN LAKE SUPERIOR BY LATE TNGT. THIS SEEMS ENTIRELY
REASONABLE...AND WAS ACCEPTED BY SPC IN PLACING THEIR MODERATE
RISK OF SVR WX OVER THE NRN PLAINS FOR TDA. IN ADDITION TO THE
SVR MCS... SOME OF THE MODELS ALSO DEVELOPED CONVECTION SWD ACRS
MN AND BROUGHT IT INTO THE FCST AREA LATE TNGT. THIS IS MORE
QUESTIONABLE. WHILE IT COULD HAPPEN...FCST SOUNDINGS FM THE AREA
WHERE THE STORMS FORM SUGGEST A STG CAP WL BE IN PLACE. WHILE A
MATURE MCS CAN EASILY BREAK SUCH A CAP...THE CAP LOOKS STG ENOUGH
TO INHIBIT THE DEVELOPMENT OF NEW STORMS AWAY FM THE MAIN
CONVECTIVE SYSTEM. IF THAT/S THE CASE...THE ONLY SIG CHC FOR
STORMS IN THE FCST AREA TNGT WL BE ACRS THE FAR N. OPTED TO PUSH
THE FCST IN THIS DIRECTION...BUT ALSO LEFT THE DOOR OPEN FOR THE
POSSIBILITY OF SOMETHING DEVELOPING FARTHER S.

EXPECT THE MAIN MCS...WEAKENING BY THIS TIME...TO BRUSH ACRS THE
N TUE MORNING...THEN PULL OFF TO THE NE. ADDITIONAL STORMS ARE
LIKELY TO FIRE ON OUTFLOW BOUNDARY FM THE MCS OR POSSIBLY RESULT
FM THE INTENSIFICATION OF SOME CONVECTION LINGERING SW OF THE
DEPARTING SYSTEM. IN EITHER CASE...THE BEST CHC SEEMS TO BE IN E-C
WI DURING THE LATE AFTN INTO THE EVENING. ALTHOUGH CONFIDENCE IN
THESE STORMS DEVELOPING IS DECENT...DID NOT GO BEYOND CHC POPS
SINCE CONVERAGE MAY BE LIMITED AS THE FLOW IN LOW LEVELS VEERS
WLY... GENERALLY UNFAVORABLE FOR GETTING SIG LOW-LEVEL
CONVERGENCE AND WIDESPREAD STORMS IN ERN WI.

THERE WL OBVIOUSLY BE A SVR RISK OVER FAR N-C WI IF THE PLAINS MCS
CAN REACH THAT AREA BEFORE WEAKENING TOO MUCH. THE MAIN THREAT WL
BE WIND. THE SECOND SVR RISK WL BE ANY REDEVELOPMENT OVER MAINLY E-C
WI TUE AFTN/EVENING. COMPLETELY CONCUR WITH THE DEPICTION OF
THESE RISKS IN THE SPC DAY 1 AND 2 CONVECTIVE OUTLOOKS.

STAYED CLOSE TO BLEND OF GUIDANCE FOR TEMPS TDA/TNGT/TUE. TEMPS
TUE ESPECIALLY TRICKY DUE TO QUESTIONS ABOUT MORNING TSTM
COVERAGE AND THE LCN OF DEBRIS CLDS FM THE DEPARING MCS...BUT
STUCK WITH VERY WARM READINGS BASED ON THE IDEA THAT THE OVERNIGHT
MCS IS MOST LIKELY TO AFFECT ONLY THE FAR N.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
ISSUED AT 409 AM CDT MON JUL 21 2014

THE LATEST GFS ENSEMBLE MEAN INDICATES THAT THE UPPER AIR PATTERN
WILL REORGANIZE NEXT WEEKEND WHEN AN EASTERN NOAM LONGWAVE TROUGH
IS ESTABLISHED. UNTIL THIS OCCURS...WEAK TROUGHING INITIALLY OVER
THE GREAT LAKES WILL FLATTEN BY THE END OF THE WORK WEEK. SOME
DIFFERENCES REMAIN WITH THE DETAILS TUESDAY EVENING BUT
OTHERWISE... THE GFS AND ECMWF ARE IN VERY GOOD AGREEMENT THROUGH
THE MEDIUM RANGE. WILL SIDE WITH THE ECMWF TUESDAY NIGHT AS MODELS
APPEAR TO BE TRENDING TOWARDS ITS GENERAL SOLUTION.

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...THE COLD FRONT WILL
CONTINUE TO MARCH SOUTHEAST ACROSS NORTHEAST WISCONSIN EARLY
TUESDAY EVENING. SHOWERS AND THUNDERSTORMS WILL BE LIKELY AHEAD OF
THE FRONT FROM THE FOX VALLEY AND BAY OF GREEN BAY ON EAST. THE
POTENTIAL FOR STRONG TO SEVERE THUNDERSTORMS WILL CARRY OVER TO
THE START OF THE EVENING...BUT SHOULD WANE QUICKLY AS ONGOING
CONVECTION STABILIZES THE ATMOSPHERE. WILL TRIM PRECIP CHANCES
BACK OVER THE WESTERN FORECAST AREA...AND ADD A LITTLE MORE
TEMPORAL RESOLUTION TO THE FORECAST. THINKING THE GFS IS A LITTLE
TOO SLOW EXITING THE PRECIP...AND WILL START SCALING BACK PRECIP
CHANCES AFTER 03Z. BEHIND THE FRONT...COOLER AND DRIER AIR WILL
PUSH SOUTHWARD ACROSS THE REGION OVERNIGHT. THEN HIGH PRESSURE
WILL BUILD INTO THE AREA ON WEDNESDAY AND STICK AROUND FOR
WEDNESDAY NIGHT. HIGHS WL RETURN TO THE 70S ON WEDNESDAY...WITH
TEMPERATURES DROPPING BACK INTO THE 40S AND 50S WEDNESDAY NIGHT.

REST OF THE FORECAST...HIGH PRESSURE WILL ENSURE A CONTINUATION
OF PLEASANT AND DRY CONDITIONS ON THURSDAY. THEN MID-LEVEL
MOISTURE STARTS TO RETURN LATE THURSDAY NIGHT INTO FRIDAY. THE
ECMWF SPITS OUT LIGHT QPF DURING THIS PERIOD BUT LOW LEVELS WILL
REMAIN DRY DUE TO THE PROXIMITY OF THE SURFACE HIGH. WILL KEEP
THURSDAY NIGHT DRY BUT EXPAND FRIDAY PRECIP CHANCES SOUTH AND
EAST. AMOUNTS SHOULD BE LIGHT AS FORCING IS WEAK. MUCH BETTER
CHANCES OF PRECIP WILL ARRIVE FRIDAY NIGHT WITH THE APPROACH OF A
SURFACE WARM FRONT AND CONTINUE THROUGH THE WEEKEND AS LOW
PRESSURE SLOWLY CROSSES THE REGION. &&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 409 AM CDT MON JUL 21 2014

HAZE/PATCHY MVR FOG EXPECTED IN E-C WI AGAIN EARLY THIS MORNING.
ONCE THAT DISSIPATES...OVERALL GOOD FLIGHT CONDITIONS ARE EXPECTED
UNTIL TSTMS ARRIVE TNGT OR TUE. WINDS ABV THE SFC TNGT WL BE
MARGINAL FOR LLWS...WL MAKE ISSUANCE TIME DECISION ON THAT.
&&

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

$$

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








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