Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 201747
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1247 PM CDT SUN JUL 20 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 408 AM CDT SUN JUL 20 2014

VERY WARM AND INCREASINGLY HUMID THE NEXT COUPLE DAYS...THEN A
ROUND OR TWO OF THUNDERSTORMS EARLY IN THE WORK WEEK.

LARGE SCALE UPR TROF WL BECOME ESTABLISHED NR THE WEST COAST THE
NEXT FEW DAYS...ALLOWING SUBTROPICAL RIDGE TO EXPAND NWD ACRS THE
CONUS. A WEAKNESS IN THE RIDGE BETWEEN ANTICYCLONE CENTERS OVER
THE DESERT SW AND THE WRN ATL WL ALLOW SOME TROFFING TO DEVELOP
OVER THE ERN CONUS MID-WEEK. THERE WAS GOOD CONSISTENCY AMONG THE
MED RANGE MODELS IN THE EVOLUTION OF THE FLOW AFTER THAT...BOTH
BETWEEN MODELS AND FROM RUN TO RUN OF EACH MODEL. THE FLOW WILL
TEMPORARILY FLATTEN LATE IN THE WEEK/EARLY NEXT WEEKEND AS A STG
SHRTWV EJECTING OUT OF THE WEST COAST TROF DRIVES THROUGH THE
RIDGE OVER THE N-C CONUS...THEN AMPLIFY STRONGLY AS THE SHRTWV
REACHES THE ERN CONUS EARLY IN THE FOLLOWING WORK WEEK.

THE BUILDING RIDGE ACRS THE RGN EARLY IN THE PERIOD WL ALLOW
TEMPS TO CONT TO EDGE UPWARD EACH DAY...WHILE PERSISENT SLY FLOW
INCREASES THE LOW-LEVEL MOISTURE. VERY WARM AND HUMID CONDITIONS
ARE EXPECTED MONDAY...AND DEPENDING ON THE BEHAVIOR OF CONVECTION
MONDAY NIGHT....POSSIBLY AGAIN ON TUESDAY. TEMPS SHOULD RETURN
CLOSER TO SEASONAL NORMALS FOR THE MIDDLE OF THE WEEK THROUGH THE
UPCOMING WEEKEND...THEN FALL TO BLO NORMAL LEVELS AFTER THAT WHEN
THE ERN U.S. UPR TROF UNDERGOES STG AMPLIFIFICATION. THE GREATEST
CHC OF PCPN WL COME IN THE MON NGT-TUE NGT TIME FRAME AS COLD
FRONT AND SHRTWV CROSS THE AREA AND INTERACT WITH THE VERY MOIST
AND UNSTABLE AIR ACRS THE RGN. AMNTS COULD BE SIGNIFICANT...AND
PCPN AMNTS FOR THE NEXT 7 DAYS WL PRIMARILY DEPEND ON WHAT FALLS
WITH THIS EVENT.
&&

.SHORT TERM...TODAY...TONIGHT...AND MONDAY
ISSUED AT 408 AM CDT SUN JUL 20 2014

MID CLDS FROM REMNANTS OF PCPN BAND THAT WAS ASSOCIATED WITH THE
FRONT THAT STALLED AND WEAKENED AWAY TO OUR W WERE CROSSING THE
AREA EARLY THIS MORNING. THE TREND THE PAST FEW MORNINGS AS BEEN
FOR THE AC DECK TO HANG TOUGH OVERNIGHT...THEN DISSIPATE QUICKLY
AFTER SUNRISE ONLY TO BE REPLACED BY SOME CU. WENT WITH THAT IDEA
AGAIN FOR TDA. STAYED CLOSE TO PREV FCST FOR MAX TEMPS. COULD
STILL SEE DWPTS MIX DOWN A BIT THIS AFTN.

THE NEXT COLD FRONT CROSSING CANADA WL APPROACH THE AREA
TNGT...BUT SHOULD STALL AND WEAKEN BEFORE GETTING HERE. SUPPORT
FOR PCPN TNGT HAS WANED IN THE MODELS...THROUGH STRENGTHENING WLY
FLOW ALOFT TO OUR NW AND AND INCREASINGLY MOIST AND UNSTABLE AIR
MASS ACRS THE AREA HINT AT SOME POSSIBILITY THAT THE REMNANTS OF
ANY STORMS THAT FIRE TO THE W TDA COULD BRUSH THE N TNGT. STAYED
WITH THE PREV FCST AND KEPT SLGT CHC POPS GOING OVER THE FAR N AND
WL LET THE NEXT SHIFT TAKE ANOTHER LOOK. EDGED MINS TOWARD THE
LOWER END OF THE GUIDANCE SPECTRUM ACRS MUCH OF THE FCST AREA
SINCE DWPTS STILL WON/T BE HIGH ENOUGH TO REALLY KEEP IT WARM AT
NIGHT.

THE FRONTAL SYSTEM AND STRONGEST FORCING WL REFOCUS BACK FARTHER
W MONDAY. THAT SHOULD LEAD TO FEWER CLDS AND EVEN WARMER TEMPS.
DEWPOINTS WILL INCREASE AS WELL. HEAT INDICES SHOULD TOP OUT IN
THE MID 90S IN MOST AREAS. THOUGH THAT/S SUB-ADVISORY /ADVISORY
CRITERIA IS 100/...ITS STILL WORTH A MENTION IN THE
HWO...ESPECIALLY SINCE WE HAVEN/T HAD A REAL HOT/HUMID DAY YET
THIS SUMMER.

AS WAS THE CASE FRI AND SAT...SLY FLOW UP THE LENGTH OF LAKE
MICHIGAN WL KEEP ANYONE NR THE LAKESHORE WONDERING WHEN SUMMER
WILL FINALLY ARRIVE. PATCHY FOG/HAZE WL RESTRICT VSBYS OVER THE
LAKE AT TIMES. THAT WL SPREAD INTO THE NRN BAY AS DWPTS INCREASE.
DWPTS WL BE HIGH ENOUGH MON TO MAKE PATCHY DENSE FOG POSSIBLE
OVER THE COLD WATERS OF WRN LAKE MICHIGAN...AND THE FOG COULD
BRUSH SHORELINE AREAS AT TIMES.

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY
ISSUED AT 408 AM CDT SUN JUL 20 2014

THE LATEST GFS ENSEMBLE MEAN INDICATES THAT SOUTHWEST FLOW ALOFT
EARLY IN THE PERIOD WILL BECOME CLOSER TO ZONAL BY NEXT WEEKEND.
AS A RESULT...HOT AND HUMID MID-SUMMER TIME WEATHER WILL BECOME
MORE SEASONABLE AS SUB-TROPICAL RIDGING GETS SHUNTED TO THE SOUTH.
LOOKING AT THE MEDIUM RANGE MODELS THIS EVENING...THEY OFFER
DIFFERENT SOLUTIONS IN REGARDS TO THE TRACK AND STRENGTH OF LOW
PRESSURE PROGGED TO CROSS THE REGION ON TUESDAY. THE ECMWF IS
STRONGER AND FARTHER NORTH THAN THE GEM AND GFS...POSSIBLY DUE TO
CONVECTIVE FEEDBACK. THINK THE ECMWF IS TOO STRONG/NORTH WHILE THE
GFS IS TOO WEAK/SOUTH SO PREFER A COMPROMISE BETWEEN THESE MODELS.
BEYOND THIS SYSTEM...THE FLOW BRIEFLY TURNS NORTHWEST AND IT SEEMS
THE ECMWF HAS A GOOD HANDLE ON THE LARGE SCALE FEATURES.

MONDAY NIGHT THROUGH TUESDAY NIGHT...SHORTWAVE ENERGY WILL BE
MOVING AROUND THE SUB-TROPICAL RIDGING AND ACROSS THE NORTHERN
PLAINS MONDAY NIGHT. AHEAD OF THE SHORTWAVE...LOW PRESSURE WILL
MOVE INTO THE NORTHERN MISSISSIPPI VALLEY WHILE A SHALLOW COLD
FRONT DROPS SOUTH ACROSS LAKE SUPERIOR AND NORTHERN MINNESOTA. A
30-40 KT LLJ ALONG WITH FGEN ALONG THE COLD FRONT WILL BE
INTERACTING WITH AMPLE ELEVATED INSTABILITY IN PLACE TO PRODUCE
MCS ACTIVITY UPSTREAM WHICH SHOULD BE APPROACHING NORTH-CENTRAL OR
CENTRAL WISCONSIN LATE MONDAY NIGHT INTO TUESDAY MORNING. SEEMS
THAT BETTER CHANCES FOR SEVERE WEATHER WILL OCCUR UPSTREAM SINCE
THE LLJ WILL BE VEERING AND/OR WEAKENING BY THE TIME IT PUSHES
INTO N-C WISCONSIN. WILL INCREASE PRECIP CHANCES OVER N-C
WISCONSIN. THE LOW PRESSURE MOVES EAST ON TUESDAY WHILE THE COLD
FRONT DROPS TO THE SOUTHEAST. SOME DISRUPTION TO DAYTIME HEATING
APPEARS POSSIBLE...BUT THE ARRIVAL OF THE FRONT DURING THE
AFTERNOON SHOULD YIELD A CHANCE OF SEVERE WEATHER. THINKING
DAMAGING WINDS AND LARGE HAIL WILL THE MAIN THREATS. THE FRONT
EXITS THE REGION TUESDAY EVENING AND NORTHERLY WINDS BEHIND THE
FRONT WILL USHER IN A COOLER AND LESS HUMID AIRMASS.

REST OF THE FORECAST...HIGH PRESSURE WILL DROP SOUTHEAST ACROSS THE
REGION WEDNESDAY AND THURSDAY...BRINGING QUIET AND SEASONABLE
CONDITIONS.  THE NEXT SYSTEM THEN MOVES IN DURING THE LATE FRIDAY
INTO SATURDAY PERIOD.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1236 PM CDT SUN JUL 20 2014

VFR CONDITIONS EXPECTED TO CONTINUE THROUGH THE PERIOD WITH MAINLY
AFTN CU...THOUGH SOME MID AND HIGH CLOUDS POSSIBLE AT TIMES AS
CONVECTION FIRES OFF TO THE NORTH OR WEST. WITH HUMIDITY
INCREASING THIS PERIOD EXPECT LIGHT FOG OR HAZE AT TIMES
ESPECIALLY ALONG THE LAKE.

&&

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

$$

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






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