Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 200208
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
908 PM CDT FRI SEP 19 2014

NEW INFORMATION ADDED TO UPDATE SECTION

.UPDATE...
ISSUED AT 854 PM CDT FRI SEP 19 2014

FORECAST FROM THE DAY SHIFT APPEARS TO BE ON TRACK. TSTMS HAVE
INCREASED OVER THE PAST HOUR IN WEST CENTRAL WI...WHERE STRONG
0-1 KM MOISTURE CONVERGENCE...THE RRQ OF A 90 KT JET STREAK AND
AN INSTABILITY AXIS (MUCAPE 1000-1500 J/KG) ARE ALIGNED. EXPECT
PCPN TO GRADUALLY SHIFT E/SE ACROSS THE FORECAST OVERNIGHT...
AS THE LLJ VEERS WEST AND THE RRQ OF THE UPPER JET PULLS THROUGH.
NOT SURE ABOUT THE COVERAGE OF THE SHRA/TSRA ACTIVITY YET...SO
WILL STICK WITH HIGH CHC POPS FOR NOW. WILL MONITOR OVER THE NEXT
HOUR AND SEE IF POPS NEED TO BE INCREASED.

STILL ANTICIPATE THE POSSIBILITY OF A FEW STRONG STORMS...AS
DEEP LAYER SHEAR IS 40-50+ KTS AND MID-LEVEL LAPSE RATES ARE
STEEP (7-8 C/KM). THE PRESENCE OF A 40-50 KT LLJ WILL ALSO
ENHANCE THE THREAT OF STRONG TSTM WINDS...ALTHOUGH MOST OF
THE INSTABILITY WILL BE ELEVATED.

&&

.SYNOPSIS...
ISSUED AT 243 PM CDT FRI SEP 19 2014

WARM AND A BIT MORE HUMID EARLY IN THE WEEKEND...THEN BRIEFLY
COOLER BEFORE TURNING MILD AND MAINLY DRY NEXT WEEK.

INITIALLY LOW- AMPLITUDE BAND OF WESTERLIES ACRS SRN CANADA AND
THE NRN CONUS WL UNDERGO AMPLIFICATION DURING THE WEEKEND...WITH
UPR RIDGE BUILDING OVER THE INTERMOUNTAIN WEST AND A TROF
DEEPENING THROUGH THE GREAT LAKES RGN. A SLOW PROGRESSION OF THE
LARGE SCALE FEATURES IS EXPECTED...WITH THE POSITIVE ANOMALY ASSOC
WITH THE WRN RIDGE SHIFTG TO THE JAMES BAY REGION BY THE MIDDLE OF
NEXT WEEK...BEFORE THE PROGRESSION SLOWS. THAT WL LEAVE HIGH UPR
HEIGHTS ACRS THE ERN CONUS LATE NEXT WEEK THROUGH THE FOLLOWING
WEEKEND...WITH THE MAIN WESTERLIES WELL TO THE N ACRS CANADA.

TEMPS WL START OUT ABV NORMAL...BRIEFLY DROP TO BLO NORMAL LEVELS
LATE IN THE WEEKEND...THEN WARM BACK TO ABV NORMAL FOR MOST OF
NEXT WEEK. THE MAIN OPPORTUNITY FOR PCPN WL OCCUR EARLY IN THE
FCST PERIOD. UPR RIDGING DOMINATING THE AREA THEREAFTER WL ALLOW
FOR ONLY SCT LGT SHOWERS AT MOST...AND QUITE POSSIBLY TOTALLY DRY
WEATHER FOR THE MIDDLE TO LATTER PART OF THE PERIOD.
&&

.SHORT TERM...TONIGHT AND SATURDAY
ISSUED AT 243 PM CDT FRI SEP 19 2014

THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW FLATTENED
MID-LEVEL TROUGHING ACROSS THE NORTHERN PART OF THE COUNTRY FROM
MONTANA TO LAKE SUPERIOR.  WITHIN THIS TROUGHING...SEVERAL
SHORTWAVES ARE MOVING TO THE EAST AND ARE CREATING AREAS OF SHOWERS
AND STORMS.  ONE AREA IS LOCATED OVER NORTHERN MINNESOTA WHILE
ANOTHER CLUSTER IS OVER FAR NORTHERN LAKE SUPERIOR.  A FEW SHOWERS
EXTENDING SOUTHWARD FROM THE LATTER CLUSTER ARE PASSING OVER N-C
WISCONSIN EARLY THIS AFTERNOON.  FOR THE REST OF THE AFTERNOON...THE
AREA TO FOCUS ON IS OVER MINNESOTA WHERE PWATS ARE GREATER THAN 1.50
INCHES BUT STILL WAITING FOR INSTABILITY TO ARRIVE.  IF THIS AREA
CAN DESTABILIZE LATER THIS AFTERNOON...COULD SEE SOME STRONG STORMS
DEVELOP.  THE SURFACE COLD FRONT TRAILS THIS AREA AND REMAINS OVER
THE EASTERN DAKOTAS.  AS THE UPSTREAM SHORTWAVES AND COLD FRONT MOVE
THROUGH THE REGION OVER THE NEXT 24 HOURS...PRECIP TIMING AND
THUNDERSTORM POTENTIAL ARE THE MAIN FORECAST CONCERNS.

TONIGHT...PIECES OF SHORTWAVE ENERGY OVER NORTHERN PLAINS WILL MOVE
INTO THE WESTERN GREAT LAKES REGION THIS EVENING.  ALONG THE LEADING
EDGE OF THIS ENERGY...MODELS SHOW A RIBBON OF DEEP MOISTURE WITH
PWATS APPROACHING 1.75 INCHES ALONG WITH INCREASING FORCING IN THE
FORM OF MID-LEVEL FGEN AND UPPER DIVERGENCE WILL SAG SOUTHEAST
ACROSS THE NORTHWEST HALF OF WISCONSIN THIS EVENING AND NORTHEAST
WISCONSIN OVERNIGHT.  VARIOUS MODELS INCLUDING THE RUC/SREF/NAM ALL
DEVELOP MORE WIDESPREAD COVERAGE OF SHOWERS AND STORMS LATE THIS
AFTERNOON OR EARLY THIS EVENING OVER WESTERN WISCONSIN COINCIDENT
WITH A RIBBON OF ELEVATED CAPES UPWARDS OF 1000 J/KG.  SPC
HIGHLIGHTS THIS AREA FOR A THREAT OF STRONG TO NEAR SEVERE STORMS.
THE FORCING AND RIBBON OF DEEP MOISTURE LOOK TO OUTRUN THIS
INSTABILITY AXIS BY LATE IN THE EVENING AND OVERNIGHT...BUT NOT OUT
OF THE QUESTION THAT A FEW STRONG STORMS (IF THEY DEVELOP) COULD
MAKE IT INTO CENTRAL WISCONSIN BY MID TO LATE EVENING BEFORE
WEAKENING THEREAFTER.  WITH THE JET OVERHEAD...STRONG GUSTY WINDS
WOULD BE THE MAIN THREAT FOLLOWED BY SMALL HAIL.  COVERAGE OF
SHOWERS AND STORMS SHOULD DIMINISH TO SCATTERED BY THE TIME THEY
REACH NE WISCONSIN OVERNIGHT.  BEHIND THE STORMS...A LOW STRATUS
DECK SHOULD SPREAD ACROSS THE AREA...WHICH COULD ALSO CREATE PATCHY
FOG IN SPOTS.  A WARM NIGHT WITH LOWS IN THE UPPER 50S TO LOWER 60S.

SATURDAY...A FEW SHOWERS AND ISOLATED STORMS WILL BE EXITING
EAST-CENTRAL WISCONSIN EARLY IN THE MORNING AND MAY ALSO HAVE A FEW
SHOWERS OVER N-C WISCONSIN AS WELL.  BUT OTHERWISE...THE DAY SHOULD
START OUT RATHER CLOUDY WITH A LOW OVERCAST DECK IN PLACE.  THE LOW
STRATUS WILL LIKELY SLOW THE HEATING CURVE FOR A FEW HOURS IN THE
MORNING...BUT SHOULD LIFT WITH MIXING BY MID TO LATE MORNING.  THE
TRAILING SURFACE FRONT WILL BE MOVING ACROSS CENTRAL AND
NORTH-CENTRAL WISCONSIN DURING THIS TIME BUT THE CLOUD COVER SHOULD
KEEP THE FRONT RELATIVELY INACTIVE.  AS IT REACHES NORTHEAST AND
EAST-CENTRAL WISCONSIN BY MIDDAY TO EARLY AFTERNOON...POTENTIAL WILL
BE THERE FOR DAYTIME HEATING TO CREATE SURFACE BASED INSTABILITY
OVER THAT PART OF THE STATE.  THE NAM GENERATES CLOSE TO 1500 J/KG
OF ML CAPE OVER EAST-CENTRAL WISCONSIN ASSUMING TEMPERATURES CAN
REACH INTO THE MIDDLE 70S.  BUT CONVERGENCE ALONG THE FRONT IS
RELATIVELY WEAK AND THERE WILL LIKELY BE A CAP TO OVERCOME.  SO
THINK THE POTENTIAL FOR REDEVELOPMENT OF THUNDERSTORMS IS PRETTY LOW
BECAUSE OF THESE FACTORS.  HIGHS IN THE UPPER 60S NORTH TO MIDDLE OR
UPPER 70S SOUTH.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
ISSUED AT 243 PM CDT FRI SEP 19 2014

UPR SPEED MAX AND SHARPENING SHRTWV WL DIG SE ACRS THE FCST AREA
SAT NGT AS LARGE SCALE AMPLIFICATION OCCURS. THE STG DYNAMICS WL
BE FAVORABLE FOR PCPN...ESP ACRS THE N. RAISED POPS TO
CATEGORICAL THERE...TAPERING TO A HIGH-END CHC ACRS THE S.
INSTABILITY WON/T BE GREAT...BUT WL PROBABLY BE SUFFICIENT FOR
THUNDER GIVEN THE DYANMICS. TRENDED TOWARD THE HIGH QPFS OF THE
MODELS WITH THE BETTER DEFINED SFC REFLECTION.

BLUSTERY...CLDY...AND MUCH COOLER CONDITIONS ARE LIKELY SUN...
WITH LINGERING SHRA OVER MAINLY THE N/NE/E. TRIMMED MAX
TEMPS...BUT WOULD NOT BE SURPRISED IF THEY END UP EVENTUALLY
NEEDING A BIT MORE PRUNING.

TEMPS SUN NGT TRICKY BECAUSE THEY/LL DEPEND ON CLDS. THINK THERE
WL STILL BE ENOUGH OF A NW FLOW DOWN ACRS LAKE SUPERIOR TO KEEP
THINGS A LITTLE CLOUDIER THAN MUCH OF THE GUIDANCE IS
INDICATING...SO DID NOT TAKE LOWS DOWN TOO FAR. A FROST/FREEZE
WOULD CERTAINLY BE POSSIBLE ACRS MUCH OF THE AREA IF WE TOTALLY
CLEAR OUT.

UPR HEIGHTS REBOUND QUICKLY LATER SUN NGT AND MON...SO THE COOLER
WX WL BE SHORT-LIVED. MODELS HINT THAT WK SHRTWVS WORKING ARND
THE WRN FLANK OF THE UPR RIDGE COULD BRUSH THE AREA AT TIMES.
THAT RESULTED IN SOME LOW-CHC POPS IN THE EXTENDED FCST
INITIALIZATION GRIDS. THAT/S CERTAINLY HARD TO RULE OUT SO LET
THOSE RIDE IN THE FCST. BUT OVERALL...FORCING WL BE WEAK AND
MOISTURE LIMITED...SO EXPECTING A MAINLY DRY PERIOD WITH ABV
NORMAL TEMPS.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 644 PM CDT FRI SEP 19 2014

SOUTH WINDS GUSTING TO 25-30 KTS WILL CONTINUE ACROSS THE REGION
EARLY THIS EVENING. LLWS IS EXPECTED TONIGHT...BUT SHOULD WEAKEN
AT THE WESTERN TAF SITES BY 09Z-10Z...AND AT THE EASTERN TAF
SITES BY 12Z-14Z/SAT.

SHOWERS AND SCT TSTMS ARE EXPECTED TO DEVELOP IN ASSOCIATION WITH
A STRONG LOW-LEVEL JET THIS EVENING...AND MAY CONTINUE LATE TONIGHT
INTO EARLY SATURDAY AS AN UPPER LEVEL JET STREAK MOVES THROUGH.
HAVE NOT INCLUDED THUNDER AT ANY OF THE TAF SITES...AS CONFIDENCE
IN THE TRENDS IS TOO LOW AT THIS TIME. VFR CONDITIONS ARE
EXPECTED BEFORE THE RAIN ARRIVES...BUT MVFR CONDITIONS SHOULD
ACCOMPANY THE FIRST ROUND OF SHOWERS AND STORMS. STRATUS IS EXPECTED
TO DEVELOP OVER NC WI LATE THIS EVG...THEN GRADUALLY WORK ITS WAY
ACROSS THE REST OF THE FORECAST AREA OVERNIGHT INTO EARLY SATURDAY.
IFR CONDITIONS ARE POSSIBLE...ESPECIALLY OVER NC/C WI. EXPECT LOW
CIGS TO GRADUALLY IMPROVE AS A COLD FRONT MOVES THROUGH THE
REGION ON SATURDAY. RIGHT NOW IT DOES NOT APPEAR THAT THERE WILL
BE SIGNIFICANT PCPN ALONG THE FRONT.
&&

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

$$

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





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