Issued by NWS Green Bay, WI
000 FXUS63 KGRB 160756 AFDGRB AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREEN BAY WI 256 AM CDT MON MAR 16 2009 .SHORT TERM...TODAY/TONIGHT/TUESDAY. A PERIOD OF MID/HIGH CLOUDS AHEAD OF A NRN STREAM SHORT WAVE WILL PASS OVER MAINLY THE MORNING HOURS. A WEAK VORT PASSING OVER IL INTO SRN WI ALSO CONTRIBUTED SOME MID LEVEL CLOUDS THIS AM. SOME WEAK RETURNS SHOWING UP OVER SRN WI THIS AM BUT NO GROUND TRUTH SO FAR...BUT LIKELY VIRGA...WHICH COULD GLANCE OVER AREAS SE OF LINE FROM OSH TO MTW THIS MORNING. SAT IMAGERY SUGGESTS DECREASING CLOUDS BY THIS AFTERNOON IN THE WAKE OF THE SW TROF. OTHERWISE THE MAIN STORY IS THE WARMER TEMPERATURES TODAY INTO TUESDAY. MOST LOCATIONS CLIMBED INTO THE LOWER OR MID 50S SUNDAY AND WITH THE FAIRLY MILD START THIS MORNING EXPECT RANGES TO BE AROUND 5 DEGREES WARMER. VERY STRONG WAA ON TUESDAY IS PROGGED AHEAD OF A COOL FRONT. H8 TEMPS CLIMB TO 12 C BY MID DAY. WAS TEMPTED TO MENTION THE UP TO 70 FOR EC WI (RECORD HIGH FOR TUESDAY MARCH 17TH IS 71) BUT THE SW FLOW HAS TO PASS OVER THE FROZEN LAKE WINNEBAGO AREA PLUS CLOUDS MAY PLAY A ROLE. WITH THE DRY AIRMASS EXPECT THE FROPA TO BE OVERALL DRY. .LONG TERM...TUESDAY NIGHT THROUGH FRIDAY. MEDIUM RANGE MODELS CONTINUE TO ADVERTISE FAIRLY LOW AMPLITUDE FLOW ACROSS NORTH AMERICA FOR THE UPCOMING WORK WEEK. A SHORTWAVE TROUGH TRIES TO AMPLIFY ACROSS THE EASTERN CONUS BY THE END OF THE WEEK...AND THE GFS SEEMS A LITTLE TOO AMBITIOUS IN THIS REGARD. PREFER THE ECMWF FOR THE END OF THE WEEK...OTHERWISE A BLEND WILL DO ONCE AGAIN. TUESDAY NIGHT AND WEDNESDAY...COLD FRONT WILL BE EXITING THE FAR SOUTHEASTERN FORECAST AREA EARLY TUESDAY EVENING. MODELS CONTINUE TO INDICATE THAT PRECIP WILL DEVELOP ALONG THE BOUNDARY TO THE SOUTH AND EAST OF THE AREA...AS MORE MOISTURE FROM THE GULF OF MEXICO BECOMES AVAILABLE. THE 00Z GFS HAS BACKED OFF A BIT IN PRODUCING FRONTOGENETICAL PRECIP ACROSS THE SOUTHERN TIER COUNTIES LATE TUESDAY NIGHT INTO WEDNESDAY MORNING...WHICH IS MORE IN LINE WITH OTHER MEDIUM RANGE MODELS. AS A RESULT...SEE NO REASON TO STRAY FROM A DRY FORECAST. COLD ADVECTION BEHIND THE FRONT BROUGHT TO YOU BY NORTHWEST WINDS WILL DROP 850MB TEMPS BELOW 0C BY LATE AFTERNOON. STEADY TEMPS IN THE MORNING...MAY ACTUALLY FALL DURING THE AFTERNOON...ESPECIALLY IF THE COLDER GFS SOLUTION WORKS OUT. A COLDER SOLUTION WILL ALSO BRING IN STRATO-CU ACROSS THE NORTH...BUT THINK THE GFS IS OVERDONE A BIT WITH THE COLD AIR. SO WILL CONTINUE TO ADVERTISE DECREASING CLOUDS THROUGH THE DAY...WHICH THE INHERITED GRIDS SHOW NICELY. WEDNESDAY NIGHT AND THURSDAY...COLD ADVECTION CONTINUES INTO WEDNESDAY NIGHT...WITH 850MB TEMPS FALLING INTO THE NEG MID TEENS ACROSS THE NORTH AND NORTHEAST. MODELS INDICATE SOME SHORTWAVE ACTIVITY WITH A POCKET OF 700-500MB -DIVQ DROPPING SOUTHEAST OVER THE FORECAST AREA LATE. NOT MUCH MID-LEVEL MOISTURE WITH THIS WAVE...BUT PROGGED SOUNDINGS SHOW THERE ARE SOME FAIRLY STEEP LOW-LEVEL LAPSE RATES WITH RESIDUAL LOW LEVEL MOISTURE SATURATED ABOUT 50-75MB THICK. SINCE THE UPWARD MOTION AS A RESULT OF THE WAVE WOULD RESIDE ABOVE THIS LEVEL...AND THERE IS A FAIRLY SIGNIFICANT INVERTED V SIGNATURE BELOW THE SATURATED LEVEL...AM SKEPTICAL IF ANY FLURRIES OR LIGHT SNOW SHOWERS WOULD BE ABLE TO FORM AND/OR REACH THE SURFACE. WILL LEAVE A CHANCE OF FLURRIES TO MATCH UP WITH OTHER OFFICES. HIGH PRESSURE BUILDS IN ON THURSDAY...BUT RELATIVELY HIGH MIXING HEIGHTS WILL ALLOW HIGHS TO APPROACH NORMAL DESPITE A COOLISH AIRMASS OVERHEAD. REST OF THE FORECAST...HIGH PRESSURE GRADUALLY SHIFTS EAST THURSDAY NIGHT ONWARD AND THE MAIN BAROCLINIC ZONES WILL RESIDE TO THE NORTHWEST AND SOUTHWEST OF WISCONSIN. 850MB TEMPS GRADUALLY MODERATE OVER THIS TIME AS WELL...WITH WARM AIR ADVECTION OCCURRING FROM THE WEST. TEMPERATURES NEAR NORMAL. MPC && .AVIATION...VFR CONDITIONS WILL PREVAIL TODAY INTO TONIGHT. AC CLOUDS PASSING OVER THIS AM APPEAR TO BE HOLDING OFF FOG AND HAZE THIS AM. WITH CLEAR SKIES AND INCREASING SURFACE DEWPOINTS FROM CONTRIBUTION OF SNOWMELT AND ADVECTION...COULD HAVE BETTER POTENTIAL OF PATCHY TO AREAS OF MVFR VSBYS DUE TO FOG/HAZE TUESDAY MORNING. && .HYDROLOGY...WITH THE WARM TEMPERATURES AND INCREASING RUNOFF FROM SNOWMELT THIS WEEK...BREAK UP OF THE ICE ON SOME RIVERS AND STREAMS COULD OCCUR OVER EC WI THIS WEEK. LACK OF PCPN RECENTLY WHICH CONTINUES THIS WEEK SHOULD PREVENT WIDESPREAD FLOODING PROBLEMS...HOWEVER SOME ICE JAMS DURING BREAK UP MAY OCCUR WHICH COULD FLUCTUATE RIVER LEVELS. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ TDH/MPC
