Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 290855
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
355 AM CDT MON SEP 29 2014

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SYNOPSIS...
ISSUED AT 348 AM CDT MON SEP 29 2014

SOME SHOWERS AND TURNING SHARPLY COLDER TODAY.

UPR FLOW ACRS NOAM CURRENTLY DOMINATED BY CLOSED AND NEARLY CUT-
OFF LOW OVER THE WRN CONUS...AN EXPANSIVE RIDGE OVER THE ERN
CONUS...AND THE MAIN WESTERLIES ACRS CANADA. THE WRN LOW WL GET
RE-ENERGIZED AS ANOTHER UPR LOW CURRENTLY OVER THE GULF OF AK
DIGS SE AND PHASES WITH IT...WITH THE RESULTING UPR TROF BECOMING
PROGRESSIVE. THE TROF WL REACH ERN NOAM BY NEXT WEEKEND...WHILE A
RIDGE FORMS OUT WEST. THE NEW PATTERN WL HAVE MODEST AMPLITUDE.

STG COLD FRONT DRIVING SWD ACRS THE AREA TDA WL BRING AN ABRUPT
END TO THE STRING OF UNSEASONABLY WARM WX. TEMPS WL CRASH TO BLO
NORMAL LEVELS BY TOMORROW...RECOVER TO NR OR A LITTLE ABV NORMAL
FOR A BRIEF PERIOD MID-WK...THEN DROP OFF TO A LITTLE BLO NORMAL
BY THE WEEKEND. PCPN IS LIKELY TO END UP AOA NORMAL FOR THE
PERIOD. WHILE SOME RN IS EXPECTED TDA...THE BULK OF THE PCPN WL
FALL DURING THE MIDDLE-LATTER PART OF THE WORK WEEK WHEN THE LARGE
SCALE UPR TROF CROSSES THE AREA.
&&

.SHORT TERM...TODAY...TONIGHT...AND TUESDAY
ISSUED AT 348 AM CDT MON SEP 29 2014

THE OVERALL FCST IS PRETTY STRAIGHTFORWARD. STG COLD FRONT WL DROP
S ACRS THE AREA THIS MORNING AND EARLY THIS AFTN. FRONTOGENETIC
FORCING COMBINED WITH QG FORCING FM FAIRLY STG SHRTWV DROPPING SE
WL RESULT IN LIFT BACK OVER THE FRONTAL SFC...AND A BAND OF POST-
FRONTAL SHOWERS. BUT THERE WERE PLENTY OF FCST DETAILS TO WORK OUT
IN THE GRIDS INCLUDING TIMING OF PCPN AND POPS...THE NON-DIURNAL
TEMPERATURE TREND TDA...WINDS IN ERN WI...AND THE POTENTIAL FOR
SOME LAKE-EFFECT CLDS AND PCPN TNGT INTO EARLY TUE.

THE FRONT IS ALREADY INTO THE FCST AREA...AND EXPECT IT TO CLR THE
AREA ARND 16Z. SHRA JUST ENTERING NW VILAS COUNTY. WENT WITH CAT
POPS FOR THE FAR N THIS MORNING...THEN STUCK WITH LIKELIES AT
BEST LATER TDA AS COVERAGE OF SHRA MIGHT NOT BE COMPLETE...ESP
OVER THE SW CORNER OF THE FCST AREA. BASED ON THE REACTION OF THE
WINDS ON ERN LAKE SUPERIOR THIS MORNING...EXPECT A PRETTY STG SWD
PUSH OF THE FRONT DOWN THE BAY. SO ADDED SOME GUSTY N-NE WINDS
MID-DAY OVER ERN WI IMMEDIATELY IN THE WAKE OF THE FRONT.

LIKED THE WAY THE RAP HELD ONTO SHRA OVER E-C WI INTO THE EARLY
EVENING...AS SHRTWV DROPPING SWD BEHIND THE FRONT WL BE PRETTY
STG. A MORE PROLONGED PERIOD OF STRONGER NNE FLOW IS LIKELY
OVERNIGHT AS 925 MB FLOW COMES ARND TO THE NNE AND COLD AIR ALOFT
RESULTS IN STG INSTABILITY OVER THE RELATIVELY WARM WATERS OF THE
LAKE AND BAY.

WAS MORE PESSIMISTIC THAN THE MAJORITY OF THE GUIDANCE IN GETTIG
RID OF THE CLDS LATER TDA/TNGT. EARLY MORNING STLT SHOWED AN
EXPANSIVE LOW-DECK BEHIND THE FRONT...AND N/NELY FLOW DOWN ACRS
LAKES SUPERIOR/MICHIGAN WL LIKELY GENERATE MORE CLDS. WOULD NOT
EVEN BE SURPRISED TO GET SOME LGT LAKE-EFFECT SHRA. JUST CARRIED
AS SPRINKLES FOR NOW. A FROST/FREEZE WOULD BE LIKELY ACRS ABOUT
THE NWRN 1/2 OF THE FCST AREA IF CLDS CLEAR OUT COMPLETELY...BUT
JUST HAVE A HARD TIME SEEING THAT HAPPENING. WENT A BIT ABV GUID
WITH MINS PRIMARILY IN THE MIDDLE 30S NW...TO MIDDLE 40S SE. DAY
SHIFT SHOULD HAVE THE BENEFIT OF TRACKING THE CLD TRENDS DURING
THE DAY...AND CAN ADJUST MINS AND POST ANY NEEDED FROST/FREEZE
HEADLINES THIS AFTN IF NECESSARY.

QUIETER WX WL RETURN TUE...BUT THE CANADIAN AIR MASS WL BE
ENTRENCHED ACRS THE AREA BY THEN SO WENT TOWARD THE LOWER END OF
THE GUIDANCE MAX TEMPS.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
ISSUED AT 348 AM CDT MON SEP 29 2014

STILL LOOKING FOR A PATTERN CHANGE TO TAKE PLACE LATER THIS WEEK AS
MEAN TROUGHING SETTLES OVER THE GREAT LAKES.  AS THE TRANSITION
OCCURS...A PERIOD OF UNSETTLED WEATHER WILL ARRIVE DURING THE
WEDNESDAY THROUGH FRIDAY TIME PERIOD.  THE MEDIUM RANGE MODELS STILL
HAVE A FEW DETAILS TO GET WORKED OUT...SINCE EACH SOLUTION HAS A
SLIGHTLY DIFFERENT TIMING/STRENGTH OF SMALLER SCALE FEATURES.  WILL
LEAN ON THE MORE CONSISTENT ECMWF...THOUGH WILL ALSO WORK IN THE
GEM.  BOTH THE ECMWF AND GEM ARE PREFERRED BY HPC.

TUESDAY NIGHT THRU WEDNESDAY NIGHT...LOW PRESSURE WILL BE MOVING
NORTH OVER THE NORTHERN PLAINS WHILE HIGH PRESSURE WILL BE SHIFTING
EAST INTO THE EASTERN GREAT LAKES.  WILL HAVE EASTERLY WINDS
EMANATING OUT OF THE HIGH TUESDAY NIGHT...FEEDING DRY AIR INTO THE
EASTERN HALF OF WISCONSIN WHICH WILL TRY TO FIGHT BACK SHOWERS
WITHIN A MID-LEVEL THETAE AXIS OVER WESTERN WISCONSIN. THINK THE DRY AIR
WILL WIN OUT AND WILL STICK WITH A DRY FORECAST.  THE BAND OF
SHOWERS WILL STALL ON WEDNESDAY AS IT LOSES ITS FORWARD PUSH.  BUT
THE EASTERN EXTENT OF THE SHOWERS COULD IMPACT NORTH-CENTRAL
WISCONSIN SO WILL INCREASE PRECIP CHANCES.  THE EAST SHOULD REMAIN
DRY WITH EAST WINDS CONTINUING.  THE BAND OF SHOWERS WILL GET SOME
FORWARD MOMENTUM WEDNESDAY NIGHT AS HEIGHT FALLS TAKE PLACE OVER THE
GREAT LAKES.  THIS SHOULD PUSH THE CHANCE OF PRECIP INTO EASTERN
WISCONSIN.  COULD SEE A FEW RUMBLES OF THUNDER BUT IN
GENERAL...INSTABILITY IS RATHER MARGINAL.  WILL DROP HIGHS OVER
CENTRAL AND NORTH-CENTRAL WISCONSIN ON WEDNESDAY DUE TO PRECIP AND
CLOUDS BUT SHOULD STILL REMAIN IN THE 60S EVERYWHERE. NO CHANGES TO
LOW TEMPS.

REST OF THE FORECAST...A CHANCE OF SHOWERS WILL CONTINUE ON THURSDAY
BUT SOME INDICATIONS OF ANOTHER SHORTWAVE ARRIVING THURSDAY
AFTERNOON THAT COULD PROVIDE ANOTHER ROUND OF WIDESPREAD PRECIP.
THE BASE OF THE AMPLIFYING WESTERN TROUGH REACHES THE STATE THURSDAY
NIGHT WHICH WILL MARK THE ARRIVAL OF A STRONG SECONDARY FRONT.  THE
CHANCE OF SHOWERS WILL CONTINUE ON FRIDAY BENEATH THE TROUGH.  THEN
PRECIP CHANCES START TO FALL FRIDAY NIGHT INTO SATURDAY WHEN THE
TROUGH AXIS SHIFTS EAST OF THE REGION.  BUT COLDER AIR WILL BE
ARRIVING BY THIS TIME...WHEN HIGH TEMPS WILL STRUGGLE TO RISE ABOVE
50 DEGREES IN SPOTS.  SOME MODERATING OCCURS ON SUNDAY BEFORE
RETURNING MOISTURE CREATES ANOTHER CHANCE OF LIGHT RAIN LATER SUNDAY
OR NEXT MONDAY.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 348 AM CDT MON SEP 29 2014

IFR CIGS ARE LIKELY ACRS NRN WI IMMEDIATELY BEHIND A COLD FRONT
DROPPING SWD ACRS THE AREA THIS MORNING. THEN CIGS ACRS THE ENTIRE
AREA SHOULD SETTLE INTO THE MVFR RANGE FOR LATER TDA INTO TNGT.
SUSPECT THE MVFR CIGS WL BE SLOWER TO DEPART THAN DEPICTED ON MANY
OF THE FCST MODELS DUE TO THE FLOW OF COLD AIR SSWWD ACRS THE GREAT
LAKES.
&&

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

$$

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






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