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000
FXUS63 KGRB 122336
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
636 PM CDT WED MAR 12 2014

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 233 PM CDT WED MAR 12 2014

TONIGHT AND WEDNESDAY.

MAIN FORECAST CONCERN FOR A RATHER UNEVENTFUL SHORT TERM WILL BE
TEMPERATURES...TIMING CLOUD COVER TONIGHT...AND THE POSSIBILITY FOR
LIGHT SNOW SHOWERS ON THURSDAY.

12Z MODEL RUNS SHOWING EITHER A DRY OR SCATTERED LIGHT SNOW
SHOWER SOLUTIONS FOR LATE TONIGHT INTO THURSDAY MORNING. WHILE THE
UPPER LEVEL FORCING WILL BE LESS ROBUST TONIGHT THAN THE SYSTEM WE
SAW THIS MORNING WHICH BROUGHT LIGHT SNOW AND ABOUT A HALF AN
INCH OF SNOW IN SPOTS...THE MOISTURE FIELD WILL BETTER FOR THIS
OVERNIGHT PERIOD AND FAIRLY STRONG WAA SHOULD AID IN ANY LACKING
SYNOPTIC SCALE FORCING. SO...ONCE AGAIN...WILL BE KEEPING THE
LIGHT SNOW IN THE FORECAST. THIS MATCHED UP WELL WITH THE ONGOING
OBS IN WESTERN MN WHERE THE MAIN AREA OF WAA WAS LOCATED
TODAY...AS CLOUDS AND A FEW SNOW SHOWERS WERE REPORTED THROUGH
THE LATE MORNING AND EARLY AFTERNOON. A LIGHT SNOW SOLUTION ALSO
FELL IN LINE WITH THE NUMERICAL GUIDANCE...WHICH HAS CONSISTENTLY
SHOWN SLIGHT CHANCE POPS FOR NE WI FOR THURSDAY MORNING. SO KEPT
ONGOING FORECAST WITH LIGHT SNOW.

WITH ABUNDANT DRY AIR CURRENTLY OVER WISCONSIN...AND WITH MODELS
SLOWING DOWN THE PROGRESSION OF THE SHORTWAVE MOVING ACROSS THE
AREA...FELT IT BEST TO SLOW DOWN THE ARRIVAL OF CLOUD COVER
AND PRECIP EASTWARD LATE TONIGHT AND ON THURSDAY. THIS THREW A
WRENCH INTO THE OVERNIGHT LOW FORECAST. CLEAR SKIES AND CALM WINDS
WILL CONTINUE LONGER THAN PREVIOUSLY EXPECTED...THEREFORE LOWERED
TEMPERATURES OVERNIGHT.

ON THURSDAY...LIGHT SNOW SHOULD OVERSPREAD THE CWA FROM WEST TO
EAST THROUGH THE MORNING...REACHING THE LAKESHORE BY NOON. SINCE
CURRENT MODELS HAVE THE SHORTWAVE AND WAA MOVING THROUGH SLOWER
THAN PREVIOUS RUNS...LIGHT SNOW SHOULD LINGER INTO THE
AFTERNOON...MAINLY IN EASTERN WISCONSIN. IN GENERALLY...A CLOUDY
DAY IS EXPECTED WITH TEMPERATURES ON THURSDAY WARMER THAN
TODAY...BUT STILL BELOW NORMAL FOR MARCH WITH MOST LOCATIONS ONLY
MAKING THE MIDDLE 30S.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 233 PM CDT WED MAR 12 2014

THE LATEST GFS ENSEMBLE MEAN INDICATES THAT ABOVE NORMAL HEIGHTS
OVER WESTERN NORTH AMERICA WILL LEAD TO DOWNSTREAM TROUGHING OVER
THE GREAT LAKES.  THIS WILL PLACE WISCONSIN WITHIN NORTHWEST FLOW
ALOFT...AND BELOW NORMAL TEMPS FOR MUCH OF THE PERIOD.  WITH
NORTHWEST FLOW OVERHEAD...THERE WILL BE A FEW CLIPPER SYSTEMS TO
POTENTIALLY IMPACT THE REGION. THE FIRST WILL ARRIVE ON LATE
THURSDAY NIGHT INTO FRIDAY AND THE MEDIUM RANGE MODELS ARE FAIRLY
COMPARABLE.  WILL USE A GENERAL BLEND.  THE SECOND CLIPPER LOOKS TO
ARRIVE ON MONDAY.  THE ECMWF/GEM ARE IN BETTER AGREEMENT THAN THE
GFS...BUT MODELS ARE DIVERGING BY THIS POINT.  WILL GIVE A SLIGHT
EDGE TO THE FORMER TWO MODELS.  CONFIDENCE BECOMES VERY LOW BY THE
TIME THE THIRD SYSTEM ARRIVES...DURING THE MIDDLE OF NEXT WEEK.

THURSDAY NIGHT THROUGH SATURDAY...DIGGING SHORTWAVE ENERGY WILL PUSH
SURFACE LOW PRESSURE TOWARDS CENTRAL LAKE SUPERIOR BY 12Z FRIDAY.
MODELS SHOW LOW AND MID-LEVEL THETAE ADVECTION WILL HAVE ALREADY
PUSHED ON TO THE EAST...WHICH WILL LEAVE PLENTY OF DRY AIR ALOFT
THROUGH THURSDAY NIGHT.  AS A RESULT...WILL KEEP A DRY FORECAST
GOING.  THE SHORTWAVE WILL QUICKLY PUSH A COLD FRONT ACROSS THE
REGION FRIDAY MORNING.  BEHIND THE COLD FRONT...MID-LEVEL MOISTURE
RETURNS WITHIN THE COMMA HEAD OF THE SHORTWAVE.  COOLING THERMAL
PROFILES COMBINED WITH BETTER SATURATION ALOFT WILL LEAD TO A CHANCE
OF PRECIP MAINLY ACROSS THE NORTHERN HALF OF THE FORECAST AREA.
THERMAL PROFILES LOOK A LITTLE TOO WARM FOR SNOW INITIALLY ON FRIDAY
BUT SHOULD COOL OFF FRIDAY EVENING ENOUGH TO CHANGE PRECIP OVER TO
ALL SNOW.  NOT LOOKING AT MUCH SNOW...PERHAPS A HALF INCH TO AN INCH
FRIDAY NIGHT ACROSS THE NORTH.  LIGHT SNOW WILL BE ENDING LATE FRIDAY
NIGHT...THEN A SHALLOW ARCTIC AIRMASS WILL BE FILTERING SOUTH ON
SATURDAY.  THE GFS IS MUCH COLDER THAN THE ECMWF AND WILL STAY
CONSERVATIVE WITH TEMPS...BUT WILL STILL DROP MAX TEMPS A DEGREE OR
TWO.

REST OF THE FORECAST...ARCTIC HIGH PRESSURE WILL MOVE ACROSS THE
REGION SATURDAY NIGHT AND SUNDAY...WHICH LOOK AWFULLY CHILLY.  TOUGH
TO SAY IF WINDS WILL FALL OFF SATURDAY NIGHT...BUT POTENTIAL WILL BE
THERE.  IF THEY DO...THEN TEMPS WILL HAVE TO BE LOWERED.  AFTER A
DRY BUT COLD DAY ON SUNDAY...THE NEXT CLIPPER ENERGY WILL BE DIVING
SOUTHEAST ACROSS THE NORTHERN PLAINS LATE SUNDAY NIGHT INTO MONDAY.
WILL HAVE A FAIRLY TIGHT TEMPERATURE GRADIENT OVER THE NORTHERN
MISSISSIPPI VALLEY...AND THESE EVENTS HAVE TENDED TO PRODUCE MORE
SNOW THAN MODELS INDICATE.  BUT THE 12Z MODELS HAVE SHIFTED WEST
WITH THE TRACK OF THE CLIPPER...SO WILL JUST LET THE ALLBLEND DO ITS
MAGIC.  EXPECT TRACK CHANGES IN THE COMING DAYS.  THE THERMAL GRADIENT
WILL BE HANGING AROUND MONDAY NIGHT AND POSSIBLY INTO TUESDAY AS
WELL...WHICH WILL KEEP THE WEATHER POTENTIALLY UNSETTLED.  WITH SUCH
LARGE SPREAD IN THE MODELS...TOO EARLY TO DETERMINE IF A MORE POTENT
SYSTEM ARRIVES BY MID-WEEK.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 532 PM CDT WED MAR 12 2014

HIGH PRESSURE WILL BRING CLEAR SKIES AND LIGHT WINDS FOR MUCH OF THE
NIGHT. WINDS WILL VEER SOUTH BY THURSDAY MORNING...WITH INCREASING
CLOUDS AND A CHANCE OF FLURRIES EXPECTED OVER NORTHERN AND CENTRAL
TAF SITES TOWARD MORNING. VFR CIGS AND -SN WILL CONTINUE TO
OVERSPREAD THE AREA AND MOVE INTO EASTERN WISCONSIN BY LATE MORNING
THURSDAY. QUESTION ON HOW LONG LOWER CLOUDS TO LINGER ON THU WITH
SOME MODELS SUGGESTING LOW LEVEL MOISTURE BECOMING TRAPPED UNDER
INVERSION. AT THIS TIME HAVE LEANED TOWARDS PROGRESSIVE SOLUTIONS.

&&

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

$$

SHORT TERM.....WOLF
LONG TERM......MPC
AVIATION.......TE