Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 220852
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
352 AM CDT WED OCT 22 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 352 AM CDT WED OCT 22 2014

AT 3 AM...A 1030 MB SURFACE HIGH WAS CENTERED OVER ONTARIO. THIS
HAS PRODUCED LIGHT WINDS ACROSS WESTERN WISCONSIN AND CLEAR SKIES
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. THIS HAS ALLOWED DENSE
VALLEY FOG TO DEVELOP IN THE WISCONSIN AND KICKAPOO RIVER VALLEYS.
MEANWHILE THE RAP SOUNDINGS CONTINUE TO SUGGEST THAT THE WINDS
ALOFT WILL CONTINUE TO INCREASE DURING THE REMAINDER OF THE
MORNING. HOWEVER WE MAY HAVE JUST ENOUGH TIME TO BUILD A SHALLOW
NOCTURNAL INVERSION THAT MAY ALLOW SOME STRATUS AND SOME PATCHY
VALLEY FOG TO DEVELOP IN THE MISSISSIPPI CHANNEL AND ITS
TRIBUTARIES.

FOR TONIGHT...THE 22.00Z MODELS ARE IN GOOD AGREEMENT THAT A SHORT
WAVE TROUGH WILL MOVE THROUGH THE REGION. THIS RESULTS...IN
MODERATE TO STRONG 900 TO 800 MB FRONTOGENESIS TO DEVELOP ALONG
AND SOUTH OF THE INTERSTATE 90 CORRIDOR AND THERE WILL MODERATE
850 MB MOISTURE TRANSPORT. OVERALL LIKE THE TIMING OF NMM AND
ARW...SO TRENDED THE PRECIPITATION CHANCES TOWARD THEM FOR
TONIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 352 AM CDT WED OCT 22 2014

ON THURSDAY...THE 22.00Z MODELS ARE VERY SIMILAR WITH THE FASTER
MOVEMENT OF THE SHORT WAVE TROUGH THROUGH THE REGION. THIS RESULT
IN A RAPID DECREASE IN THE 900 TO 800 MB FRONTOGENESIS AND THE
850 MB MOISTURE TRANSPORT MOVING EAST OF THE AREA BY THE
AFTERNOON. THIS RESULTS IN A QUICK DECREASE IN THE PRECIPITATION
FROM WEST TO EAST DURING THE MORNING AND EARLY AFTERNOON. THIS
SEEMS TO BE HANDLED REALLY WELL IN THE ARW AND NMM...SO TRENDED
PRECIPITATION TIMING AND PLACEMENT CLOSER TO THEM. ALSO MODEL
SOUNDINGS SHOW A RAPID DECREASE IN CLOUD COVER ALONG AND WEST OF
THE MISSISSIPPI RIVER DURING THE AFTERNOON. THIS PROVIDES A BETTER
OPPORTUNITY THAT WE COULD POTENTIALLY SEE THE PARTIAL SOLAR
ECLIPSE DURING THE LATE AFTERNOON.

ON FRIDAY...ALL OF THE MODELS ARE IN GENERAL AGREEMENT THAT A
SHORT WAVE TROUGH WILL MOVE EAST THROUGH THE AREA. THE NAM
SOUNDINGS HAVE A MUCH DEEPER MOISTURE PROFILE AND STRONGER 850 MB
MOISTURE TRANSPORT THAN THE GFS...GEM...AND ECMWF. AS A RESULT...
IT GENERATES SHOWERS AND THE OTHER MODEL SOLUTIONS ARE DRY. DUE TO
THIS...OPTED TO KEEP THE PERIOD DRY. 850 MB TEMPERATURES CLIMB 2
TO 4C WARMER THAN THURSDAY. MIXING 875 MB TEMPERATURES TO THE
SURFACE RESULTS IN TEMPERATURES MUCH CLOSER TO THE 22.03Z SREF
THAN THE SUPER BLEND...SO TRENDED THEM MORE TOWARD THE LATTER.

FROM FRIDAY NIGHT INTO SATURDAY...AN ANOMALOUSLY STRONG 150 KNOT
200 MB JET ROUNDING THE EASTERN PERIPHERY OF THE UPPER LEVEL
RIDGE. THE 21.12Z NAEFS STANDARDIZED ANOMALY SHOWED THAT A JET
THIS STRONG HAD A RETURN FREQUENCY OF ONCE IN EVERY 5 YEARS. THIS
RESULTS IN A RETROGRESSION OF THIS RIDGE WHICH IN TURN ALLOWS
COOLER 850 MB TEMPERATURES TO MOVE BACK INTO THE REGION. THERE IS
A 6 TO 8C DROP ACROSS WESTERN WISCONSIN AND 4 TO 6C ACROSS
SOUTHEAST MINNESOTA AND NORTHEAST IOWA. DUE TO THIS...LOWERED THE
MAXIMUM TEMPERATURES ANYWHERE FROM 2 TO 6 DEGREES.

ON SUNDAY...THE UPPER LEVEL RIDGE REESTABLISHES ITSELF ACROSS THE
AREA AS A LONG WAVE TROUGH MOVES EAST INTO THE WESTERN UNITED
STATES. 850 MB TEMPERATURES RISE 6 TO 8C INTO THE 10C TO 14C
RANGE. THESE TEMPERATURES ARE AROUND 1.8 STANDARD DEVIATIONS ABOVE
NORMAL. THE SUPER BLEND LOOKS TOO COLD...SO RAISED THE HIGH
TEMPERATURES CLOSER TO THE BIAS CORRECTED GFS AND ECMWF.

FROM SUNDAY NIGHT INTO TUESDAY...THE MODELS ARE DIFFERING ON THE
TRACK OF A STRENGTHENING LOW PRESSURE SYSTEM MOVING THROUGH THE
REGION. THE GFS IS MUCH FURTHER THAN EITHER THE ECMWF OR GEM. DUE
TO THIS...STAYED CLOSED TO THE MODEL CONSENSUS FOR TEMPERATURES
AND PRECIPITATION CHANCES.

&&

.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...BOYNE
LONG TERM...BOYNE
AVIATION...04



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