Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 190722
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
225 AM CDT SAT JUL 19 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 225 AM CDT SAT JUL 19 2014

LIKELY GOING TO HAVE TO ISOLATED SHOWER/STORMS ACROSS PARTS OF THE
REGION THIS WEEKEND...BUT MORE PLACES THAN NOT WILL STAY DRY.

WEAK PERTURBATIONS IN THE UPPER LEVEL FLOW WILL SERVE AS KICKERS FOR
SHOWERS/STORMS TODAY AND SUNDAY. THE INSTABILITY AXIS HOLDS TO THE
WEST THOUGH...GENERALLY ACROSS THE EASTERN NORTHERN PLAINS/WESTERN
MN. THE BETTER SHEAR ALSO HOLDS HERE. WHILE THE MAIN THRUST OF LOW
LEVEL MOISTURE TRANSPORT ALSO STAYS IN THIS NEIGHBORHOOD...A BRANCH
IS EXPECTED TO FOLLOW THE CURRENT SHORTWAVE KICKING OFF THE PCPN
OVER NORTHERN MN EARLY THIS MORNING. THIS POINTS INTO NORTHERN
WI...AND THUS MOST OF THE SMALL PCPN THREAT SHOULD ALSO LIE THERE.

ON SUNDAY...ANOTHER BIT OF ENERGY COULD TAKE A SIMILAR TRACK...AND
INTERACT WITH SOME OF THIS LOW LEVEL MOISTURE TO TRIGGER A FEW MORE
SHOWERS/STORMS. STILL...AS IT MOVES EAST...IT WILL MOVE OUT OF THE
BETTER INSTABILITY.

IN ADDITION...WARMING TEMPS THIS WEEKEND WILL LEAD TO A LOW LEVEL
INVERSION. THIS LOW LEVEL STABILITY WILL REQUIRE SOME SORT OF
FORCING MECHANISM TO GET CONVECTION GOING...AND IF THE BITS OF
ENERGY STAY NORTH...SO WILL THE CHANCES.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 225 AM CDT SAT JUL 19 2014

WHILE THE PCPN CHANCES ARE NOT CLEAR CUT FOR THE WEEKEND...THERE IS
BETTER AGREEMENT IN THE MODELS FOR INCREASING SHOWER/STORM CHANCES
TUE-WED. BOTH THE GFS AND ECMWF DRIVE AN UPPER LEVEL SHORTWAVE
TROUGH ACROSS THE NORTHERN PLAINS MON NIGHT...SLIDING IT ACROSS THE
GREAT LAKES TUE/TUE NIGHT. ASSOCIATED SFC LOW CURRENTLY PROGGED TO
MOVE EAST ACROSS CENTRAL MN...KEEPING ITS WARM FRONT TO THE NORTH OF
THE FORECAST AREA. EXPECT SHOWERS/STORMS ALONG AND NORTH OF THE WARM
FRONT...WHERE THE BETTER UPPER LEVEL FORCING ALSO WOULD LIE.
HOWEVER...A COLD FRONT WILL RUN SOUTH OF THE LOW...AND WILL HAVE
INSTABILITY AND LOW LEVEL MOISTURE TO PLAY WITH. GOING TO NEED THAT
FRONT TO KICK OFF CONVECTION...WITH 700 MB TEMPS 12+ C AND BUFKIT
SOUNDINGS SHOWING A DECENT INVERSION. LATE TUE AFTERNOON-TUE NIGHT
LOOKING FAVORABLE AT THIS TIME FOR PERIODS OF SHOWERS/STORMS. THIS
WILL LIKELY LINGER INTO WED MORNING BEFORE CLEARING EAST. DEPENDING
ON TIMING...THERE COULD BE A STRONG/SEVERE THREAT AS THE SYSTEM
MOVES IN.

MON/TUE SHOULD ALSO KICK THE NEW WORK WEEK OFF TO A SOMEWHAT HOT
START. 925 MB TEMPS WARM INTO THE MID 20S WHILE 850 MB TEMP
ANOMALIES VIA THE EC CLIMB NEAR +2. MID TO UPPER 80S HIGHS ARE
LIKELY FOR MOST...WITH A FEW LOCATIONS FLIRTING WITH 90. DEWPOINTS
WILL ALSO BE CLIMBING...WHICH MAKES HEAT INDICES A FACTOR. SOME
PARTS OF SOUTHEAST MN/NORTHEAST IA COULD REACH 100 DEGREES FOR A
HEAT INDEX MON/TUE AFTERNOONS. DON/T ANTICIPATE A HEAT ADVISORY AT
THIS TIME. THAT SAID...IF TEMPS OR DEW POINTS CLIMB JUST A DEGREE OR
TWO MORE THAN WHAT IS CURRENTLY EXPECTED...ONE COULD BE NEEDED.

THE GFS AND ECMWF STILL POINTING FOR BROAD UPPER LEVEL RIDGING TO
ZONAL TYPE FLOW OF THE MIDDLE PART OF NEXT WEEK...WITH A SFC HIGH
MAKING ITS WAY SOUTHEAST ACROSS THE EASTERN GREAT LAKES. DRY
CONDITIONS ARE FAVORED WED NIGHT-FRIDAY. LIKELY SOME COOL DOWN FOR
THU POST THE EARLY WEEK COLD FRONT...BUT PROBABLY ONLY A FEW DEGREES
BELOW THE JULY NORMALS.

DECENT AGREEMENT IN THE MODELS WITH TRACKING A CLOSED 500 MB LOW
EAST ACROSS SOUTHERN CANADA...BRINGING IT TO THE ND/CANADIAN BORDER
LATE FRI NIGHT. A SFC FRONT WILL BE FOUND WELL AHEAD OF THE UPPER
LEVEL FORCING...BUT THERE WILL BE A DECENT FETCH OF LOW LEVEL
MOISTURE...RIDING IN ON A 35-40 KT 850 MB JET...TO PAIR WITH IT.
WEAK MUCAPE ALSO INDICATED IN THE GFS. ALTHOUGH TIMING STILL A BIT
SUSPECT...FRI NIGHT/SAT BECOMING MORE FAVORABLE FOR SHOWER/STORM
CHANCES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT) ISSUED AT
1143 PM CDT FRI JUL 18 2014

VFR CONDITIONS ARE EXPECTED ON SATURDAY WITH THE MAIN FOCUS BEING ON
WHETHER ANY RAIN SHOWERS OR THUNDERSTORMS WILL MAKE IT INTO THE TAF
REGION. CHANCES ARE PRETTY SLIM AS THE DEEPER FORCING AND MORE
UNSTABLE AIR MASS WILL RESIDE TO THE WEST...BUT SOME OF THE FORECAST
GUIDANCE IS SUGGESTING THAT SOME SHOWERS WILL DEVELOP IN THE
AFTERNOON AND EVENING HOURS...MORE SO IN SOUTHEAST MINNESOTA.
CONFIDENCE IS NOT HIGH ENOUGH IN THESE SHOWERS/STORMS HITTING
RST...SO HAVE NOT ADDED TO THE TAF YET. OTHERWISE SOME GUSTY WINDS
UP TO 20KTS WILL BE POSSIBLE SATURDAY WITH MID TO UPPER LEVEL CLOUD
COVER MOVING THROUGH AT TIMES.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION.....HALBACH


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