Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 191941
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
245 PM CDT SUN APR 19 2015

.SHORT TERM...(TONIGHT THROUGH TUESDASY)
ISSUED AT 245 PM CDT SUN APR 19 2015

SCATTERED SHWERS RANGE FROM NORTHERN WI INTO NORTHEAST IA...WITH
LARGER AREA OF SHOWERS AND A FEW STORSM OVER SOUTHWEST IA. ANOTHER
AREA OF RAIN WAS MOVING NORTH ACROSS CENTRAL ILL.

COLD FRONT TRACKING EAST ACROSS THE REGION TONIGHT...WITH GOOD
FROTOGENETIC FORCING ASSOCIATED WITH IT. QG FORCING INCREASES IN THE
850-500 MB LAYER THIS EVENING...ALONG THE FRONT AND JUST AHEAD OF AN
APPROACHING UPPER LEVEL TROUGH. TO THE SOUTH...A SHORT WAVE
TROUGH/SFC LOW ARE GOING TO STAY SOUTH...SLIDING ACROSS IL INTO
MICH. TRACK WILL SERVE TO BRING SOME MOISTURE NORTHWARD INTO WI
THOUGH...HELPING TO FUEL SHOWER CHANCES. ALL THE FORCING SHOULD
RESULT IN A BLOSSOMING AREA OF PCPN THIS EVENING...WITH MODEL
CONSENSUS FAVORING MISSISSIPPI RIVER-WEST THIS EVENING...GRADUALLY
EASING EAST OVERNIGHT. THE RAIN WILL THEN CONTINUE TO LIFT EAST
NORTHEAST THROUGH THE REST OF MON MORNING.

CYCLONIC FLOW A LOFT AND COLD AIR ADVECTION MON/TUE SETS THE STAGE
FOR SOME SHOWER POTENTIAL. GOOD LOW/MID LEVEL LAPSE RATES ALONG WITH
A 100-200 MB LAYER OF WEAK INSTABLITY ABOVE 800 MB MON/TUE
AFTERNOONS...PER BUFKIT SOUNDINGS. BITS OF UPPER LEVEL ENERGY
PROGGED TO SPIRAL AROUND THE 500 MB LOW...WITH MODEL CONSENSUS ON
DRIVING A PIECE ACROSS THE FORECAST AREA TUE AFTERNOON. RH FIELDS
KEEP THE DEEPEST SATURATION ACROSS THE NORTH...BUT ENOUGH SHOULD BE
AROUND TO FUEL THE INSTABLITY SHOWER THREAT. TUE LOOKING LIKE THE
HIGHER PROBABILITY DAY WITH THE ADDITION OF THE RIPPLE IN THE UPPER
LEVEL FLOW.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 245 PM CDT SUN APR 19 2015

MODELS IN GOOD AGREEMENT WITH A PATTERN SHIFT FOR THE UPCOMING WEEK.
THE UPPER LEVEL TROUGH WILL HOLD FAST ACROSS SOUTHEAST CANADA...WITH
THE RESULTING NORTHWEST FLOW PROVIDING A CONTINUOUS FETCH OF
UNSEASONABLY COLD AIR. 850 MB TEMPS FALL FROM AROUND 8 C TODAY...TO
-8 C BY TUE. EXPECTING HIGHS 10 TO 15 DEGREES BELOW NORMAL INTO NEXT
WEEKEND. ASIDE FROM THE START OF THE NEW WORK WEEK...THE PATTERN
FAVORS DRY CONDITIONS FOR THE LOCAL AREA.

MODELS START TO STRAY FROM EACH OTHER TOWARD FRIDAY WITH THE EC/GEM
FAVORING SOME UPPER LEVEL RIDGE BUILDING WHILE THE GFS PREFERS TO
HOLD ONTO THE TROUGH TROUGH THE WEEKEND. OBVIOUS IMPACTS ON TEMPS
//COOL WOULD CONTINUE WITH GFS - RETURN TO NORMAL WITH GEM/EC // BUT
SCENARIOS STILL LEAN ON THE DRY SIDE. NOT SOLD WE/LL BREAK OUT OF
THE COOL PATTERN...BUT GOING TO LEAN ON THE CONSENSUS SOLUTION FOR
THE DETAILS.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON) ISSUED
AT 1236 PM CDT SUN APR 19 2015

MAIN TAF CONCERNS ARE THUNDERSTORM CHANCES AT BOTH RST AND LSE TAF
SITES LATE THIS AFTERNOON INTO THE EARLY EVENING HOURS...THEN IFR TO
MVFR CEILING CONDITIONS THIS AFTERNOON INTO MONDAY MORNING. THE
LATEST SURFACE ANALYSIS SHOWS LOW PRESSURE OVER THE CENTRAL PLAINS
STATES WITH A COLD FRONT EXTENDING NORTH INTO CENTRAL MINNESOTA.
LATEST 19.12Z NAM SUGGEST SOME ELEVATED INSTABILITY TO DEVELOP ALONG
AND JUST AHEAD OF THE COLD FRONT BY 20Z TODAY AND QUICKLY WEAKENS
THE INSTABILITY AROUND 00Z MONDAY. AS THE FRONT PUSHES EAST THIS
AFTERNOON...THE LIFT ASSOCIATED WITH THE FRONT WILL ALLOW SHOWERS TO
DEVELOP...WITH A FEW EMBEDDED THUNDERSTORMS. WILL CONTINUE TO
MENTION VCTS AT BOTH RST AND LSE TAF SITES BETWEEN 20Z TODAY- 01Z
MONDAY.

NEXT CONCERN ARE MVFR TO IFR CEILING CONDITIONS AT THE TAF SITES.
THE 19.12Z NAM/GFS SHOW LOW LEVEL SATURATION TO OCCUR ALONG THE COLD
FRONT THIS AFTERNOON. THE 19.12Z NAM BUFKIT SOUNDINGS INDICATE MVFR
CONDITIONS AT BOTH TAF SITES THROUGH MONDAY MORNING HOURS...AND
SUGGEST THE POSSIBILITY OF IFR CONDITIONS AT RST TAF SITE THIS
EVENING INTO THE EARLY MORNING HOURS. FOR NOW...WILL CONTINUE MVFR
CEILING CONDITIONS AT BOTH RST/LSE TAF SITES AROUND 12-15Z MONDAY
AND LET LATER SHIFTS TO MONITOR IF IFR CONDITIONS DEVELOP.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION.....DTJ


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