Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 150923
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
423 AM CDT TUE APR 15 2014

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND WEDNESDAY
ISSUED AT 421 AM CDT TUE APR 15 2014

A POTENTIAL WINTER STORM FOR WEDNESDAY IS THE MAIN FCST CONCERN.

CLEAR TO PARTLY CLOUDY SKIES AND DECRASING WINDS HAVE CAUSED TEMPS
TO DROP OFF EARLY THIS MORNING...WITH READINGS AS COLD AS THE SINGLE
DIGITS ABOVE AND BLO ZERO IN NORTHERN WI.

AN UPPER LEVEL TROF WILL SHIFT EAST OF THE REGION TODAY...BUT A WEAK
S/W TROF AND A 110 KT JET STREAK WILL AFFECT NE WI DURING THE MIDDAY
PERIOD. KEPT A CHANCE OF FLURRIES IN THE FCST OVER NE WI...BUT A VERY
DRY AIR MASS AND WEAK DYNAMICS SHOULD PRECLUDE MUCH MORE THAN THAT.
USED A BLEND OF THE BETTER PERFORMING GUIDANCE SETS FOR TEMPS...
WHICH YIELDED HIGHS IN THE UPPER 20S NORTH TO THE LOWER TO MIDDLE
30S SOUTH...ROUGHLY 20 TO 25 DEGREES BLO NORMAL.

DYNAMICS WILL INCREASE ACROSS WSTRN WI LATE TONIGHT...AS A LOW
PRESSURE SYSTEM MOVES INTO SE SD. THE RRQ OF AN UPPER LEVEL
JET...H8 WAA ON THE NOSE OF A 50 KT LLJ AND INCREASING MID-LEVEL
FRONTOGENETIC FORCING WILL CAUSE SNOW TO DEVELOP OVER NW/WC WI.
PATCHY LIGHT SNOW SHOULD WORK ITS WAY INTO OUR WSTRN COUNTIES
AFTER 09Z...BUT WILL ONLY CARRY SLGT CHC OR CHC POPS FOR NOW.

DYNAMICS WILL TAKE AIM ON GRB CWA ON WEDNESDAY...WITH MODELS ALL
GENERATING SIGNIFICANT PCPN OVER OUR NORTHWEST/NORTHERN COUNTIES...
BUT TAPERING OFF TO LITTLE OR NOTHING IN THE SOUTHERN FOX VALLEY/
LKSHR AREAS. ALTHOUGH THE AIR MASS WILL BE COLD ENOUGH FOR SNOW
OVER THE ENTIRE FORECAST AREA EARLY IN THE DAY...THE RAIN/SNOW LINE
IS EXPECTED TO STEADILY SHIFT NORTH DURING THE DAY. H8 TEMPS AND
LOW-LEVEL THICKNESSES INDICATE THAT THE PCPN SHOULD FALL AS ALL
SNOW OVER THE FAR NORTH...WHERE THE WINTER STORM WATCH IS CURRENTLY
IN PLACE. TEMP/RH/OMEGA TIMESECTIONS OVER NORTHERN WI SHOW A DEEP
DENDRITIC GROWTH ZONE...AND AN IMPRESSIVE CROSSHAIRS SIGNATURE...
WHICH SUPPORTS A THREAT OF MODERATE TO HEAVY SNOWFALL. EXPECT MOST
OF THE WATCH AREA TO RECEIVE 3 TO 6 INCHES OF SNOW DURING THE
DAY...WITH A FEW INCHES OF SLUSHY SNOW EXPECTED IN THE BORDERING
COUNTIES JUST SOUTH OF THE WATCH. AFTER COORD WITH DLH/MQT/ARX...
HAVE DECIDED TO LET THE DAY SHIFT TAKE ANOTHER LOOK AT THE 12Z
MODELS BEFORE MAKING FINAL DECISIONS ON WARNING/ADVISORY
HEADLINES.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
ISSUED AT 421 AM CDT TUE APR 15 2014

THE LATEST GFS ENSEMBLE MEAN INDICATES THAT UPPER RIDGES OVER THE
EASTERN PACIFIC AND WESTERN ATLANTIC WILL TRANSLATE SLOWLY TO THE
EAST OVER THE NEXT WEEK.  DEEP TROUGHING BETWEEN THESE FEATURES WILL
GRADUALLY WEAKEN AS THE PATTERN DEAMPLIFIES...BUT WILL STILL LEAD TO
MOSTLY BELOW NORMAL TEMPERATURES FOR THE PERIOD.  THE MAIN FORECAST
CONCERN IN THIS PERIOD OF THE FORECAST IS THE DIGGING SHORTWAVE
WHICH REINFORCES THE MEAN CENTRAL NOAM TROUGH DURING THE
WEDNESDAY-THURSDAY TIMEFRAME.  LOOKING AT THE LATEST OPERATIONAL
GUIDANCE...MODELS HAVE A WIDE RANGE OF SURFACE LOW TRACKS IN THIS
PERIOD...RANGING FROM THE SOUTHERN SOLUTIONS OF THE GFS/ECMWF...AND
THE NORTHERN SOLUTIONS OF THE NAM/SREF.  THE NORTHERN SOLUTION OF
THE NAM/SREF IS LIKELY DUE TO A DEEPER SHORTWAVE COMPARED TO OTHER
GUIDANCE.  THE TRACK/STRENGTH OF THE ECMWF AND GFS COMPARE WELL WITH
THE GFS ENSEMBLE MEAN AND WILL RELY ON THEIR SOLUTIONS.

WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...LOW PRESSURE WILL BE MOVING
NORTHEAST FROM NORTHEAST IOWA TO FAR NORTHEAST WISCONSIN WEDNESDAY
NIGHT.  NORTH OF THIS LOW TRACK...VERY GOOD MID-LEVEL FGEN WILL
RESIDE ON THE NOSE OF THE LLJ AND IN THE VICINITY OF THE RIGHT REAR
QUAD OF THE UPPER JET.  PWATS ARE NOT NEARLY AS IMPRESSIVE AS THE
PAST WEEKEND SYSTEM...BUT THE INTENSE LIFT SHOULD STILL LEAD TO BAND
OF MODERATE TO HEAVY PRECIP OVER NORTHERN WISCONSIN DURING THE EVENING.
EAST WINDS NORTH OF THE SURFACE LOW TRACK SHOULD BE ABLE TO KEEP A
STEADY FLOW OF DRY POLAR AIR OVER NORTHERN WISCONSIN WHERE PROFILES
SUGGEST PTYPES OF ALL SNOW.  THIS MATCHES FAIRLY WELL WITH THE
LOCATION OF THE WINTER STORM WATCH.  NOT EXPECTING MUCH OF MIX ZONE
BETWEEN THE SNOW TO THE NORTH AND RAIN TO THE SOUTH.  USING A 10:1
RATIO...AN ADDITIONAL 2-4 INCHES APPEARS POSSIBLE WEDNESDAY EVENING
BEFORE THE DRY SLOT PUNCHES OVERHEAD AFTER MIDNIGHT.  NO CHANGES TO
THE WATCH AT THIS TIME.  NOT OUT OF THE QUESTION THAT SOME LIGHT
SNOW COULD REACH AS FAR SOUTH AS WAUSAU RIGHT BEHIND THE LOW...BUT
NOT EXPECTING MUCH ACCUMULATION.  COLDER AIR WILL FILTER IN BEHIND
THE LOW LATE WEDNESDAY NIGHT INTO THURSDAY...WHICH WILL LIKELY KEEP
LIGHT SNOW GOING FOR THE SNOW BELTS OF N-C WISCONSIN.  BUT WITH
MID-LEVEL DRYING OCCURRING...WILL END PRECIP CHANCES EARLIER ACROSS
ALL BUT N-C AND FAR NE WISCONSIN.  THE FRONTAL BOUNDARY LEFT OVER
FROM THE PREVIOUS SYSTEM WILL LINGER ACROSS THE SOUTHERN GREAT LAKES
ON THURSDAY NIGHT AND MODELS REGENERATE PRECIP ALONG IT.  NORTHERLY
WINDS BEHIND THE FRONT WILL BE PLAYING A BIG ROLE IN DETERMINING HOW
FAR NORTH PRECIP REACHES.  THINK PRECIP WILL BE FARTHER SOUTH AND
WILL DROP POPS ACROSS THE NORTHERN HALF OF THE FORECAST AREA.

REST OF THE FORECAST...HIGH PRESSURE WILL BE BUILDING INTO THE AREA
ON FRIDAY WHEN SKIES WILL BE GRADUALLY CLEARING.  HIGHS ON FRIDAY
MAY NOT BE MUCH DIFFERENT THAN THURSDAY.  THEN THE ECMWF STARTS TO
BRING IN PRECIP ON SATURDAY IN THE RIGHT REAR QUAD OF ANOTHER JET
STREAK...BUT THIS LOOKS A TAD FAST.  WILL INSTEAD FOCUS ON SATURDAY
NIGHT ON SUNDAY.  NOT LOOKING AT A LOT OF PRECIP...BUT ISENTROPIC
ASCENT LOOKS SUFFICIENT TO KEEP A CHANCE MENTION.  TEMPS CONTINUE TO
MODERATE THROUGH THE WEEKEND INTO EARLY NEXT WEEK.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1009 PM CDT MON APR 14 2014

A FEW FLURRIES WILL END ACROSS MANITOWOC COUNTY WILL END THIS EVENING.
MEANWHILE...AN UPPER LEVEL DISTURBANCE WILL BRING A SMALL CHANCE OF
LIGHT SNOW SHOWERS ACROSS THE FAR NORTH TONIGHT INTO TUESDAY MORNING.
VFR CONDITIONS SHOULD PREVAIL ACROSS THE REGION TONIGHT AND TUESDAY.
NORTH/NORTHWEST WINDS WILL BACK TO THE WEST/SOUTHWEST ON TUESDAY...
THEN BECOME LIGHT AND VARIABLE EARLY TUESDAY EVENING BEFORE BECOMING
EAST/SOUTHEAST LATER TUESDAY EVENING INTO WEDNESDAY MORNING. NEXT
SYSTEM WILL BRING AROUND OF HEAVY SNOW TO FAR NORTHERN WISCONSIN
WEDNESDAY INTO THURSDAY MORNING.
&&

.HYDROLOGY...
ISSUED AT 421 AM CDT TUE APR 15 2014

MANY RIVERS AND STREAMS REMAINED ABOVE BANKFULL BUT A LITTLE BELOW
FLOOD STAGE DUE TO RECENT HEAVY PCPN AND SNOW MELT...BUT WERE
HOLDING FAIRLY STEADY EARLY THIS MORNING DUE TO COLD TEMPERATURES.
COOL TEMPERATURES AND DRY CONDITIONS TODAY AND TONIGHT SHOULD
LIMIT POTENTIAL FOR FLOODING. THE NEXT WEATHER SYSTEM IS EXPECTED
TO PRODUCE SIGNIFICANT PCPN OVER NORTH CENTRAL AND FAR NORTHEAST
WISCONSIN ON WEDNESDAY AND WEDNESDAY NIGHT...BUT MUCH OF IT WILL
FALL AS SNOW OVER THE FAR NORTH. WE COULD SEE SOME MINOR RISES IN
RIVER LEVELS AGAIN BY THE WEEKEND AS TEMPERATURES IN THE 40S MELT
THE SNOW OVER NORTHERN WI.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
MORNING FOR WIZ005-010>012.
&&

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......MPC
AVIATION.......ECKBERG
HYDROLOGY......KIECKBUSCH






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