Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 232215
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
515 PM CDT MON MAR 23 2015

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 228 PM CDT MON MAR 23 2015

THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW ONE
SHORTWAVE EXITING THE REGION OVER SOUTHERN LAKE MICHIGAN...WHILE
ANOTHER SHORTWAVE IS MOVING SOUTHEAST OVER NORTHERN MINNESOTA.  MID
AND HIGH CLOUDS ARE PULLING OUT OVER NORTHERN LAKE MICHIGAN
ASSOCIATED WITH THE FIRST SHORTWAVE...BUT ANOTHER ROUND OF CLOUDS
IS INCOMING FROM THE LATTER SHORTWAVE...ALONG WITH LIGHT SNOW OVER
NORTHERN MINNESOTA. PLENTY OF DRY AIR PRESENT ACCORDING TO THE 12Z
SOUNDING BELOW 700MB WHICH THE UPSTREAM LIGHT SNOWFALL WILL HAVE TO
OVERCOME IF IT SURVIVES THE TRIP INTO N-C WISCONSIN LATER TODAY.
PLENTY OF LOW CLOUDS ARE LINGERING OVER CENTRAL WISCONSIN ALONG A
LOW LEVEL THERMAL GRADIENT...BUT THE DRY AIR IS HALTING ANY ADVANCE
TO THE NORTHEAST.  CONCERNS THROUGH TOMORROW AFTERNOON ARE RELATIVELY
MINOR...AND CENTER AROUND CLOUDS AND TEMPS.

TONIGHT...A COMPACT SHORTWAVE WILL MOVE ACROSS NORTHEAST WISCONSIN
THIS EVENING.  EVEN THOUGH THERE IS LIGHT SNOW AHEAD OF IT
CURRENTLY...IT WILL RUN INTO MUCH DRIER AIR BELOW 10KFT AS IT MOVES
INTO NORTHERN WISCONSIN.  PROGGED SOUNDINGS SHOW THIS DRY AIR WEDGE
WELL TONIGHT...SO THINK WE WILL ONLY SEE SCATTERED TO BROKEN
MID-CLOUDS THROUGH THE EVENING...THEN CLEARING SKIES OVERNIGHT.
TEMPS FALLING INTO THE TEENS IN THE NORTH AND LOW TO MID 20S SOUTH.

TUESDAY...DRY CANADIAN HIGH PRESSURE HANGS ON FOR ONE MORE DAY.
WILL SEE INCREASING CIRRUS DURING THE AFTERNOON AHEAD OF A STORM
SYSTEM MOVING OVER THE CENTRAL PLAINS...BUT SHOULD SEE A GOOD DEAL
OF SUNSHINE. 925MB TEMPS CONTINUE TO BE CHILLY WITHIN THIS AIRMASS
SO DROPPED MAX TEMPS A DEGREE.  HIGHS MAINLY IN THE LOW TO MID 40
EXCEPT COOLER NEAR THE LAKE.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 228 PM CDT MON MAR 23 2015

SYSTEM FOR TUESDAY NIGHT INTO WEDNESDAY MORNING STILL PROBLEMATIC
WITH RESPECT TO EXACT TRACK OF THE SYSTEM...AMOUNT OF WARM AIR AT
THE SURFACE AND ALOFT...AND AMOUNT OF EVAPORATIVE COOLING THAT
WILL TAKE PLACE THAT MAY WIPE OUT THE WARM LAYER.

CONTEMPLATED A WINTER STORM WATCH DUE TO THE IMPACTS THIS SYSTEM
WOULD HAVE ON THE ROADS AND FOR THE MORNING RUSH HOUR. PER
COORDINATION WITH SURROUNDING OFFICES...DECIDED TO GO WITH A
SPECIAL WEATHER STATEMENT TO HIGHLIGHT THE IMPACTS OF THIS SYSTEM.
WITH SYSTEM TRENDING FURTHER SOUTH...THIS WILL HAVE IMPACTS ON
PRECIPITATION TYPES AND SNOW AMOUNTS ACROSS THE FORECAST AREA.
ADDED MORE SNOW TO THE FORECAST DUE TO THE COLDER TEMPERATURES
AT THE SURFACE AND ALOFT THAN PREVIOUS SHIFT. TO SHOW YOU THE
COMPLEXITY OF THE FORECAST...GRB NAM BUFKIT SOUNDING INDICATED
0.4 INCHES OF ICE WHILE THE GFS SUPPORTED 3 TO 5 INCHES OF SNOW.
TRENDED TOWARD THE GFS SOLUTION SINCE CANADIAN/ECMWF MODEL
SUPPORTED THE COLDER GFS SOLUTION. ALSO...THE SPEED OF THE SYSTEM
WAS OF CONCERN. HEAVIEST PRECIPITATION WOULD FALL IN ABOUT A 6 HOUR
PERIOD. THOSE TYPE OF EVENTS USUALLY DO NOT GET US TO WARNING CRITERIA.

SYSTEM WILL EXIT THE REGION WEDNESDAY MORNING WITH COLD CYCLONIC
FLOW NOTED INTO THE FIRST PART OF THE WEEKEND. CHANCE OF RAIN OR
SNOW WILL LINGER INTO THURSDAY BEFORE DRIER AIR ARRIVES. THE NEXT
CHANCE FOR RAIN OR SNOW WOULD BE SATURDAY NIGHT AND SUNDAY.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 515 PM CDT MON MAR 23 2015

SURFACE HIGH PRESSURE SYSTEM ANCHORED OVER THE GREAT LAKES REGION
WILL PROVIDE VFR CONDITIONS TONIGHT INTO TUESDAY. DETERIORATING
CONDITIONS ANTICIPATED TUESDAY NIGHT AS A STRONG FRONTAL SYSTEM
LIFTS TOWARD WISCONSIN. THE LOWERING CIGS AND VSBYS WILL INCLUDE A
WINTRY MIX OF SNOW SLEET AND FREEZING RAIN.
&&

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

$$

SHORT TERM.....MPC
LONG TERM......ECKBERG
AVIATION.......TDH





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