Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 222310
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
610 PM CDT FRI MAY 22 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 244 PM CDT FRI MAY 22 2015

PRIMARY CONCERN IN THE SHORT TERM INCLUDES SMALL CHANCE FOR RAIN
TONIGHT WITH THE INITIAL WEAK SHORT WAVE TROUGH MOVING INTO THE
AREA...AND THE EVENTUAL ONSET OF BETTER RAIN CHANCES AS THE LARGER
SYSTEM MOVES IN.

19Z NEPHANALYSIS SHOWS HIGH PRESSURE AND CLEAR SKIES ACROSS THE
GREAT LAKES REGION...WITH HIGH CIRRUS INVADING IA/IL AND ADJACENT
PORTIONS OF MN/WI. SATELLITE WATER VAPOR IMAGERY CONFIRMS MODEL
ANALYSIS OF A LARGE LONG WAVE TROUGH ALONG THE WEST COAST...WITH
INITIAL SHORT WAVES MOVING NORTH THROUGH NEBRASKA AND ALSO EAST
ACROSS ARIZONA. FIRST ELONGATED TROUGH IS SHEARING AS IT WORKS
NORTH INTO THE MEAN RIDGE ALOFT. WITH THIS DISSIPATING TREND...
COMBINED WITH RATHER DRY AIR IN PLACE OVER THE AREA...ANY RISK FOR
RAIN WILL BE QUITE LOW. VARIOUS MESOSCALE AND DETERMINISTIC MODELS
HINT AT SOME WIDELY SCATTERED LIGHT SHOWER ACTIVITY...BUT MOISTURE
IS VERY LIMITED. CONSIDERED ADDING MENTION OF SPRINKLES FOR LATE
TONIGHT INTO EARLY SATURDAY...BUT FEEL THIS WILL BE FEW AND FAR
BETWEEN IF AT ALL. ATTENTION THEN TURNS TO THE EVENTUAL ONSET OF
BETTER RAIN CHANCES AS DEEPER MOISTURE AND INSTABILITY SURGES
NORTH ACROSS THE PLAINS AND INTO THE UPPER MIDWEST BY LATE
SATURDAY. MAIN SHORT WAVE TROUGH EMBEDDED IN THE LONG WAVE LOOKS
TO REMAIN WELL WEST OF THE REGION. BUT DO ANTICIPATE CONVECTION TO
FORM GENERALLY ALONG I-35 FROM KS INTO OK. THIS ACTION SHOULD
CREATE A FEW MESOSCALE VORTICIES WHICH WILL THEN MOVE NORTH TOWARD
OUR AREA. TRYING TO TIME THAT IS DIFFICULT...BUT DO ANTICIPATE
THOSE...ALONG WITH THE NEXT LOBE OF SHORT WAVE ENERGY...SHOULD
INVADE OUR AREA LATE SATURDAY NIGHT...INTO SUNDAY MORNING. TRENDED
RAIN CHANCES IN THAT DIRECTION IN THE GRIDDED FORECAST DATABASE.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 244 PM CDT FRI MAY 22 2015

LONG WAVE TROUGH OVER THE INTERMOUNTAIN WEST OVER THE WEEKEND WILL
FILL AND SHIFT NORTHWARD AS WE MOVE INTO NEXT WEEK. GENERAL
TROUGHINESS WILL THEN LINGER ACROSS THE REGION THROUGH AT LEAST
LATE MONDAY. UPPER LEVEL PATTERN THEN TRANSITIONS INTO A SOMEWHAT
ZONAL REGIME FOR THE REMAINDER OF THE WEEK. THE BEST CHANCE FOR
ANY DRY WEATHER APPEARS TO BE FROM TUESDAY INTO WEDNESDAY WITH THE
AREA GENERALLY BETWEEN THE INFLUENCE OF ANY PARTICULAR LARGER
DISTURBANCE. BUT THERE IS A GREAT DEAL OF UNCERTAINTY AS THE MESSY
FLOW PATTERN SHOWS ANYTHING BUT CONSISTENCY BETWEEN MODEL SOLUTIONS
AND FROM RUN TO RUN. CONFIDENCE IN DETAIL IS LOW BEYOND MONDAY.
BUT IT DOES APPEAR AT LEAST THAT ANY COOLER AIR WILL REMAIN
BOTTLED UP IN CANADA...SO TEMPERATURES LOOK TO BE NEAR OR SLIGHTLY
ABOVE NORMAL THROUGH THE PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 610 PM CDT FRI MAY 22 2015

HIGH PRESSURE OVER THE OHIO RIVER VALLEY WILL REMAIN NEARLY
STATIONARY OVERNIGHT WITH THE RIDGE AXIS EXTENDING ACROSS THE
UPPER MIDWEST. THE CENTER OF THE HIGH IS EXPECTED TO MOVE INTO THE
EASTERN PART OF THE COUNTRY SATURDAY BUT THE RIDGE AXIS WILL ONLY
SHIFT SLIGHTLY TO THE NORTH. VFR CONDITIONS ARE EXPECTED THROUGH
THE PERIOD WITH THIS PATTERN. HOWEVER...WITH THE INCREASING SOUTH
FLOW BEHIND THE RIDGE AXIS AND AHEAD OF AN AREA OF LOW PRESSURE
COMING OUT OF THE ROCKIES...ENOUGH MID LEVEL MOISTURE WILL START
TO SPREAD IN AND LOWER THE CEILINGS TO THE 5 TO 10 THOUSAND FOOT
RANGE.

&&

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

$$

SHORT TERM...MW
LONG TERM...MW
AVIATION...04



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