Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 220452
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1152 PM CDT TUE OCT 21 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 255 PM CDT TUE OCT 21 2014

QUIET WEATHER CONDITIONS ARE EXPECTED THROUGH TOMORROW AFTERNOON
AS A RIDGE OF HIGH PRESSURE TRACKS EAST THROUGH THE GREAT LAKES.
THE LAST CHUNK OF STRATUS IN CENTRAL WISCONSIN HAS QUICKLY BEEN
DISSIPATING THIS AFTERNOON AND WILL COMPLETELY CLEAR OUT BY LATE
THIS AFTERNOON. WINDS ARE COMING AROUND TO THE SOUTHEAST AND
INCREASING IN THE LOW LEVELS...WHICH SHOULD MITIGATE HOW
WIDESPREAD ANY RIVER VALLEY FOG CAN GET TONIGHT.

THE MAIN FOCUS INTO TOMORROW AFTERNOON IS WITH WHETHER ANY
SPRINKLES OR LIGHT RAIN SHOWERS WILL FALL IN A BAND OF LOW LEVEL
WARM AIR ADVECTION AHEAD OF THE NEXT TROUGH. 21.12Z NAM/GFS
FORECAST SOUNDINGS SHOW SOME SATURATION OCCURRING BETWEEN
850-750MB THOUGH ANY LIFT IS VERY WEAK AND MAY NOT BE ENOUGH TO
PRODUCE THE SHOWERS. WITH CONFIDENCE NOT VERY HIGH IN WHETHER
ANYTHING WILL FORM...HAVE KEPT THE FORECAST DRY THROUGH THE LATE
AFTERNOON TOMORROW.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 255 PM CDT TUE OCT 21 2014

THE TWO MAIN STORIES GOING INTO THE EXTENDED PERIOD IS WITH THE
RAIN CHANCES WEDNESDAY NIGHT INTO THURSDAY AFTERNOON FOLLOWED BY
THE WARMUP COMING THIS WEEKEND.

AS FOR THE RAIN CHANCES...CONFIDENCE IS FAIRLY HIGH THAT THERE
WILL BE SOME RAIN THAT MOVES THROUGH WEDNESDAY NIGHT INTO
THURSDAY...BUT THE QUESTION IS WITH HOW LONG IT WILL
LAST/ACCUMULATE. BEYOND THE INITIAL 850-750MB WARM AIR
ADVECTION...THE LIFT COMES IN A FAIRLY NARROW BAND ALONG A
700-500MB TROUGH. THERE IS SOME FRONTOGENESIS THERE AS WELL IN THE
MID LEVELS...BUT THE BETTER PV ADVECTION APPEARS TO TRACK TO THE
NORTH AND EAST OF THE REGION AS THE MAIN TROUGH DIGS SOUTHEASTWARD
ACROSS THE WESTERN GREAT LAKES. THE 21.12Z ECMWF APPEARS TO BE THE
STRONGEST WITH ITS LIFT SINCE IT BREAKS OFF A PIECE OF THE 500MB
TROUGH AND PROPAGATES IT FURTHER SOUTHEAST COMPARED TO THE OTHER
GUIDANCE. HAVE GENERALLY GONE WITH A TENTH OF AN INCH TO UNDER A
HALF INCH OF QPF FOR THIS SYSTEM SINCE THE MOISTURE FEED IS IN
THIS NARROW CHANNEL. THE MAIN TRENDS WITH THE 21.12Z GUIDANCE IS
TO SPEED UP THE CLEARING OF THE RAIN THURSDAY AFTERNOON WITH THE
21.12Z ECMWF THE SLOWEST AND THE MAIN REASON THAT THERE EVEN ARE
ANY PRECIPITATION CHANCES LEFT IN THE FORECAST AFTER 18Z THURSDAY.

ALL SIGNS CONTINUE TO POINT TO A WARM WEEKEND AHEAD...PARTICULARLY
ON SUNDAY WHEN STRONG SOUTHERLY LOW LEVEL ADVECTION KICK IN AHEAD
OF THE NEXT SYSTEM. STANDARDIZED ANOMALIES FOR TEMPERATURES AT
925/850MB ARE NOT T00 HIGH AT +1 TO +2...BUT STILL HELP TO SIGNAL
THAT CONDITIONS WILL BE ABOVE NORMAL. HAVE CONTINUED THE TREND OF
KEEPING FORECAST HIGHS ABOVE GUIDANCE WITH HIGHS IN THE 60S TO LOW
70S.

THE NEXT SYSTEM MOVES IN ON MONDAY/TUESDAY AND SHOULD BE THE NEXT
CHANCE FOR SOME WIDESPREAD HEAVIER RAINS AS A SURFACE LOW RUNS UP
FROM THE SOUTHERN PLAINS INTO THE UPPER MISSISSIPPI RIVER VALLEY.
SOME TIMING/INTENSITY DIFFERENCES BETWEEN THE 21.12Z GFS/ECMWF BUT
THE OVERALL MESSAGE IS SIMILAR.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1152 PM CDT TUE OCT 21 2014

SOME CONCERN FOR VALLEY FOG AT KLSE LATE TONIGHT. BOTH THE 22.00Z
NAM AND 22.03Z RAP SHOW SATURATION OCCURRING AT THE SURFACE BUT
SUGGEST THE WINDS ABOVE THE SURFACE WILL BE IN THE 15 TO 20 KNOT
RANGE. THE FLAG HERE AT THE OFFICE IS MOVING A LITTLE BIT BUT NOT
AS MUCH AS WOULD BE ANTICIPATED BASED ON THE MODEL WINDS AND A BIT
OF A HAZE LAYER APPEARS TO BE SHOWING UP OVER THE CITY. AS THE
GRADIENT BETWEEN THE LOW LEVEL RIDGE OVER THE GREAT LAKES AND THE
APPROACHING COLD FRONT CONTINUES TO TIGHTEN OVERNIGHT...WOULD
EXPECT THE WINDS ALOFT TO CONTINUE SLOWLY INCREASING WHICH SHOULD
CREATE ENOUGH MIXING TO KEEP THE FOG FROM FORMING.
HOWEVER...CONFIDENCE IN THIS IS NOT THAT HIGH AND WILL INCLUDE A
BCFG TO INDICATE THE POSSIBILITY OF SOME FOG. THE GRADIENT SHOULD
PRODUCE DECENT SUSTAINED SOUTH WINDS WEDNESDAY AND WITH GOOD
MIXING...GUSTS BETWEEN 20 AND 25 KNOTS SHOULD OCCUR AT KRST. AS
THE COLD FRONT APPROACHES WEDNESDAY EVENING...SHOULD START TO SEE
ENOUGH MID LEVEL MOISTURE ARRIVE FOR A VFR CEILING TO FORM AT
KRST. THE RAIN WITH THE FRONT IS EXPECTED TO HOLD OFF UNTIL AFTER
MIDNIGHT.

&&

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

$$

SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...04



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