Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 190812
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
312 AM CDT SUN OCT 19 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 312 AM CDT SUN OCT 19 2014

LATEST WATER VAPOR SATELLITE IMAGERY SHOWING UPPER LEVEL TROUGH OVER
THE NORTHEASTERN UNITED STATES AND SHORTWAVE TROUGH EMBEDDED IN
NORTHWEST FLOW OVER THE NORTHERN PLAINS AND SOUTHERN
MANITOBA/SASKATCHEWAN CANADA. LATEST FOG PRODUCT SATELLITE
INDICATE MID LEVEL CLOUDS IN ASSOCIATION WITH SHORTWAVE TROUGH.
THE SHORTWAVE TROUGH IS PRODUCING SCATTERED LIGHT RAIN
SHOWERS/SPRINKLES OVER SOUTHERN MANITOBA...EASTERN NORTH DAKOTA AND
NORTHWEST MINNESOTA PER MOSAIC RADAR.

MAIN FORECAST CONCERNS ARE SMALL PRECIPITATION CHANCES ACROSS NORTH
CENTRAL WISCONSIN THIS AFTERNOON...THEN CLOUDS TONIGHT.

THE 19.00Z GFS/NAM ARE IN GOOD AGREEMENT IN PUSHING AND DEEPENING
SHORTWAVE TROUGH OVER THE UPPER MIDWEST AND GREAT LAKES REGION TODAY
INTO TONIGHT. MINOR DIFFERENCES ARE INDICATED BETWEEN THE 19.00Z
GFS/NAM WITH THE GFS SLIGHTLY FASTER IN MOVING SHORTWAVE TROUGH THAN
THE NAM. BOTH THE 19.00Z MODELS ARE SHOWING DECENT PV ADVECTION AND
QG FORCING ABOVE 700MB IN ASSOCIATION WITH THE SHORTWAVE TROUGH LATE
THIS AFTERNOON INTO TONIGHT. HOWEVER...THE BIGGEST CONCERN WILL BE
SATURATION OF THE ATMOSPHERE COLUMN...AS THE LATEST 19.00Z UPPER AIR
SOUNDINGS ACROSS THE UPPER MIDWEST INDICATES VERY DRY MID LEVEL
AIRMASS OVER THE AREA. THIS WILL INHIBIT ANY PRECIPITATION REACHING
THE GROUND OVER MUCH OF THE FORECAST AREA TODAY INTO TONIGHT. WITH
THE BETTER LIFT AND DEEPER MOISTURE OVER NORTH CENTRAL
WISCONSIN...THERE IS THE POSSIBILITY OF AN ISOLATED SHOWER OR
SPRINKLES TO OCCUR AND HAVE INTRODUCE A SMALL PRECIPITATION CHANCE
OVER TAYLOR COUNTY LATE THIS AFTERNOON. THE 19.00Z GFS/NAM TIME
CROSS SECTIONS SHOW SUBSIDENCE OVER THE AREA TONIGHT AND MOISTURE
QUICKLY EXITING THE FORECAST AREA AFTER 03Z MONDAY. CURRENT
FORECAST HAS GOOD HANDLE ON SKY TRENDS TONIGHT ACROSS FORECAST
AREA...WITH MOSTLY CLEAR/PARTLY CLOUDY SKIES.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 312 AM CDT SUN OCT 19 2014

MONDAY INTO TUESDAY NIGHT...AS THE SHORTWAVE TROUGH DIGS OVER THE
EASTERN UNITED STATES...THE 19.00Z GFS/NAM SHOW MOISTURE AT 850MB
AND BELOW ADVECTING INTO WESTERN AND CENTRAL WISCONSIN AFTER 12Z
MONDAY. THIS MOISTURE REMAINS OVER THE EASTERN PARTS OF THE FORECAST
AREA THROUGH MUCH OF THE DAY MONDAY AND PRODUCE STRATO/CUMULUS DECK
OF CLOUDS OVER THIS AREA. THE 19.00Z GFS/NAM ARE IN DECENT AGREEMENT
IN BUILDING SURFACE RIDGE AND HEIGHT RISES OVER THE UPPER MIDWEST
AND NORTHERN PLAINS MONDAY NIGHT INTO TUESDAY. WITH SUBSIDENCE AND
DRIER AIRMASS ADVECTING INTO THE FORECAST AREA...THIS SHOULD ALLOW
CLOUDS TO ERODE OVER THE EASTERN FORECAST AREA MONDAY NIGHT AND
BECOME MOSTLY SUNNY ACROSS MUCH OF THE FORECAST AREA TUESDAY.

MAIN FORECAST CONCERNS WEDNESDAY INTO SATURDAY ARE PRECIPITATION
CHANCES WEDNESDAY NIGHT INTO THURSDAY...THEN TEMPERATURES FOR REST
OF THE PERIOD. THE 19.00Z GFS/ECMWF/GEM ARE IN GOOD AGREEMENT IN
BUILDING UPPER RIDGE INTO THE CENTRAL UNITED STATES WEDNESDAY AND
ADVECTING WARMER AIR INTO THE FORECAST AREA...WITH 850MB
TEMPERATURES WARMING TO PLUS 10 TO PLUS 13 DEGREES CELSIUS BY 00Z
THURSDAY. THEN...SIGNIFICANT DIFFERENCES OCCUR BETWEEN THE 19.00Z
MODELS ON HOW FAST TO BREAK DOWN UPPER LEVEL RIDGE AND
PLACEMENT/MOVEMENT OF UPPER LEVEL LOW/TROUGH MEANDERING OVER THE
SOUTHERN AND CENTRAL UNITED STATES WEDNESDAY NIGHT INTO THURSDAY
NIGHT. ALSO...MAJOR DIFFERENCES OCCUR BETWEEN THE MODELS WITH THE
DEVELOPMENT OF THE UPPER LEVEL FLOW PATTERN ACROSS THE CONTINENTAL
UNITED STATES FRIDAY INTO SATURDAY. WHERE...THE 19.00Z GFS BY 12Z
FRIDAY HAS UPPER LEVEL RIDGE OVER THE NORTHERN PLAINS...THE 19.00Z
ECMWF HAS SHORTWAVE RIDGING OVER THE GREAT LAKES REGION AND
DEVELOPS WESTERLY FLOW OVER THE NORTHERN PLAINS...AND THE 19.00Z
GEM DEVELOPS WEST TO NORTHWESTERLY FLOW ALOFT OVER THE NORTHERN
TIER STATES. DUE TO ALL OF THESE INCONSISTENCIES...THIS WILL HAVE
IMPACTS ON SMALL PRECIPITATION CHANCES WEDNESDAY NIGHT INTO
THURSDAY AND TEMPERATURES FRIDAY INTO SATURDAY ACROSS THE FORECAST
AREA. CONFIDENCE IN FORECAST FROM WEDNESDAY NIGHT INTO SATURDAY
IS LOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1100 PM CDT SAT OCT 18 2014

LIGHT SFC/NEAR SFC WIND FIELD WITH HIGH PRESSURE OVERHEAD SUGGESTS
SOME POTENTIAL FOR RIVER VALLEY FOG. T/TD SPREAD WAS 6 F AT
03Z...GOOD INDICATOR FOR DENSE FOG. HOWEVER...THERE ARE A COUPLE
DRAWBACKS. FIRST IS THE HIGH PRESSURE SLIPS SOUTHEAST
OVERNIGHT...ALLOWING FOR THE WINDS RIGHT ABOVE THE NOCTURNAL
INVERSION TO INCREASE. RAP BUFKIT SOUNDING INCREASING TO 14KTS AT
200 FT BY 07Z. THE SECOND IS SCT-BKN HIGH/MID LEVEL CLOUDS MOVING IN
FROM THE WEST...AHEAD OF AN UPPER LEVEL SHORTWAVE TROUGH. THINK SOME
THIN BR/STRATUS WILL DEVELOP ALONG THE RIVER...BUT MAY NOT SPREAD
OUTSIDE OF ITS BANKS. WILL CONTINUE TO KEEP KLSE FOG FREE FOR
NOW...BUT IT WILL NEED MONITORING.

HIGH/MID LEVEL CIGS FOR A PORTION OF THE DAY SUNDAY...WITH
INCREASING SOUTHERLY WINDS BY MID MORNING. EXPECT A FEW HIGHER
GUSTS...WITH SUSTAINED AROUND 15KTS OR SO. WINDS WILL BECOME
WESTERLY SUNDAY NIGHT AS THE SHORTWAVE/S SURFACE FRONT MOVES
THROUGH. NOT EXPECTING ANY PCPN.


&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION.....RIECK


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