000
FXUS63 KARX 251125
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
625 AM CDT SAT MAY 25 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 230 AM CDT SAT MAY 25 2013

LOW/MID LEVEL FRONTOGENETIC FORCING...COUPLED WITH SOME LOW LEVEL
MOISTURE TRANSPORT AND A BIT OF UPPER LEVEL ENERGY...WERE HELPING
CONTINUE AN AREA OF EAST/SOUTHEAST MOVING SHOWERS. TRENDS IN THE
LATEST HRRR/NAM12 IS TO DIMINISH THIS ACTIVITY THROUGH THE PRE DAWN
HOURS...WHILE FIRING CONVECTION OVER THE SOUTHERN PLAINS/WESTERN IA.
SATELLITE IMAGERY AND RADAR RETURNS ALREADY SHOW THIS
HAPPENING...WHERE THE NOSE OF THE LOW LEVEL JET/MOISTURE TRANSPORT
WAS LOCATED. THIS COMPLEX SHOULD MOVE EAST THROUGH THE REST OF THE
MORNING INTO THE AFTERNOON...RIDING ALONG AND NORTH OF A WARM FRONT.

THIS REGION SHOULD SERVE AS THE FOCUS FOR MORE SHOWER/STORM
DEVELOPMENT TONIGHT...WITH THE LOW LEVEL JET REASSERTING ITSELF AND
SOME UPPER LEVEL ENERGY MOVING OUT OF A WEST COAST TROUGH. EASTWARD
MOVEMENT WOULD AGAIN BE FAVORED...KEEPING THE BULK OF THE PCPN SOUTH
OF THE FORECAST AREA.

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 230 AM CDT SAT MAY 25 2013

HIGH CONFIDENCE ITS GOING TO RAIN ACROSS PARTS OF THE REGION THROUGH
THE UPCOMING WORK WEEK. TIMING AND PLACEMENT IS MORE SHAKY.

THE FORECAST KEYS ON A FEW AREAS...A SFC WARM FRONT...LOW LEVEL
JET/MOISTURE TRANSPORT...AND VARIOUS MCVS. WHERE THESE ELEMENTS ALL
COME TOGETHER WILL BE WHERE THE GREATER THREAT FOR RAIN WILL LIE.
CLARITY FOR THE MESOSCALE VORTICIES/SPAWNING GROUNDS AND MOVEMENT
IS THE MAIN STICKING POINT FOR INCREASING CONFIDENCE.

THE UPPER LEVEL PATTERN IS SLOW TO PROGRESS EAST AS THERE IS LITTLE
IMPETUS VIA 250/300MB JET INTERACTION - RELATIVELY QUIET A LOFT.
SO...THE 500 MB RIDGE WILL REMAIN ACROSS THE UPPER MISSISSIPPI RIVER
VALLEY/GREAT LAKES INTO AT LEAST THE MIDDLE PART OF THE NEW WORK
WEEK...WITH A BROAD TROUGH OVER THE WEST COAST. BITS OF ENERGY WILL
SPIN OUT OF THE TROUGH...AND THEN ENHANCE VIA CONVECTION SPAWNED BY
IT AND THE LOW LEVEL JET/MOISTURE TRANSPORT. WITH THE RIDGE OVERHEAD
THE NEXT FEW DAYS...AND THE SFC WARM FRONT HOLDING TO THE
SOUTH...THESE UPPER AIR INFLECTIONS ARE PROGGED TO RIDE ALONG AND
NORTH OF THE WARM FRONT...KEEPING THE BEST RAIN CHANCES JUST SOUTH
-BUT NOT COMPLETELY OUT- OF THE FORECAST AREA.

THE WARM FRONT WILL START TO LIFT NORTH ON TUE...A FAIRLY CONSISTENT
SIGNAL IN THE NAM/GFS/ECMWF. HOW FAR NORTH IS NOT THOUGH...WITH THE
GFS APPEARING THE MORE AGGRESSIVE IN HOW FAR NORTH AND HOW FAST.
RAIN CHANCES LOOK TO BECOME MORE WIDESPREAD FOR THE FORECAST AREA
MON-TUE AS A RESULT.

DEPENDING ON HOW QUICKLY AND HOW FAR NORTH THE WARM FRONT MAKES
IT...THE AREA COULD GET INTO THE WARM SECTOR...WHICH WOULD HELP CAP
OFF THE ATMOSPHERE TO CONVECTION - OUTSIDE OF A KICKER MOVING IN.

MODEL DIFFERENCES START TO BECOME BIGGER AS WE MOVE TOWARD NEXT
WEEKEND...WITH THE EC SUGGESTING A CLOSED LOW WILL DEVELOP IN THE
WEST COAST TROUGH...SLOWLY PUSHING EAST ACROSS THE UPPER MISSISSIPPI
RIVER VALLEY NEXT WEEKEND. THIS COULD LAY UP A SFC TROUGH ACROSS THE
REGION FOR SEVERAL DAYS. THE GFS IS MORE PROGRESSIVE...MOVING THE
UPPER LEVEL ENERGY NORTHEAST...BUT STILL HAS A COUPLE SFC BOUNDARIES
THAT COULD ACT AS SHOWER/STORM PRODUCERS. WILL LIKELY STAY WITH THE
CONSENSUS SOLUTION FOR THE DETAILS IN THIS PART OF THE FORECAST.

AS FOR STORM CHANCES...INSTABILITY IS LIMITED THE NEXT COUPLE
DAYS...AND SO SHOULD BE THE THUNDERSTORMS. THE CHANCE FOR BOOMERS
WILL INCREASE WITH THE ENCROACHMENT OF THE WARM FRONT...AND
SUBSEQUENT INCREASE IN CAPES. DON/T SEE A SIGNIFICANT THREAT FOR
ORGANIZED SEVERE WEATHER THROUGH NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 625 AM CDT SAT MAY 25 2013

VFR CONDITIONS ARE EXPECTED AT THE TAF SITES INTO THIS EVENING.
SCATTERED SHOWERS WILL MOVE ACROSS THE AREA THIS MORNING AS A WEAK
UPPER LEVEL DISTURBANCE MOVES THROUGH. SHOWERS AND THUNDERSTORMS
WILL FOCUS ACROSS NORTHEAST IOWA AND FAR SOUTHWEST WISCONSIN BY
LATE THIS MORNING. A WARM FRONT WILL REMAIN NEARLY STATIONARY OVER
THE CENTRAL PLAINS/MID MISSISSIPPI RIVER VALLEY. THE FRONT IS
EXPECTED TO SLOWLY DRIFT NORTH AND UPPER LEVEL IMPULSES
INTERACTING WITH IT WILL BRING PERIODS OF SHOWERS AND
THUNDERSTORMS TO THE AREA. THE LOWER LEVELS OF THE ATMOSPHERE LOOK
TO FINALLY MOISTEN ENOUGH TO ALLOW FOR SOME MVFR CEILINGS...WITH
CLOUD BASES JUST UNDER 3KFT...TO EDGE INTO KRST AROUND 09Z
TONIGHT. CONFIDENCE IS LOW WITH THIS SCENARIO SINCE DRY LOW LEVEL
AIR IS IN PLACE OVER THE REGION.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...WETENKAMP