Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 271747
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1247 PM CDT SUN JUL 27 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 321 AM CDT SUN JUL 27 2014

LATEST WATER VAPOR SATELLITE IMAGERY INDICATING UPPER LEVEL CLOSED
LOW OVER NORTHERN MINNESOTA. LATEST MOSAIC RADAR SHOWING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS ACROSS NORTHERN MINNESOTA IN
ASSOCIATION WITH PV ADVECTION WITH CLOSED UPPER LEVEL LOW PER LATEST
RAP.

MAIN CONCERN TODAY INTO THIS EVENING IS TIMING OF THE SHOWERS AND
ISOLATED THUNDERSTORMS INTO AND EXITING THE FORECAST AREA. THE
LATEST 27.00Z GFS/NAM CONTINUE TO SHOW STRONG PV ADVECTION AND DEEP
FORCING IN ASSOCIATION WITH THE CLOSED UPPER LEVEL LOW. THE
27.00Z GFS/NAM ARE IN GOOD AGREEMENT IN TIMING THE CLOSED LOW TO
MOVE SOUTH AND EAST OF THE FORECAST AREA AND THE VERTICAL MOTION
ASSOCIATED WITH THE CLOSED LOW BY 00Z MONDAY. TRENDED
PRECIPITATION CHANCES TO EXIT THE AREA BY 03Z MONDAY. THE 27.00Z
GFS/NAM SHOW WEAK ELEVATED INSTABILITY OVER THE FORECAST AREA AND
WILL CONTINUE MENTION THE POSSIBILITY OF THUNDERSTORMS.

SURFACE RIDGE BUILDS INTO WESTERN MINNESOTA AND THE
EASTERN DAKOTAS TONIGHT AND PROVIDE MOSTLY CLEAR SKIES AND A
DRIER AIRMASS ACROSS THE FORECAST AREA.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 321 AM CDT SUN JUL 27 2014

MONDAY INTO TUESDAY...MAIN CONCERN IS THE POSSIBLE DIURNALLY DRIVEN
PRECIPITATION CHANCES. THE 27.00Z GFS/NAM DIG UPPER LEVEL TROUGH
OVER THE EASTERN UNITED STATES AND TRACK A COUPLE OF WEAK IMPULSES
EMBEDDED IN THE NORTHERLY FLOW ALOFT OVER PARTS OF THE FORECAST AREA.
BUFKIT SOUNDINGS SUGGEST MONDAY REMAINS DRY ACROSS THE AREA.
HOWEVER...BUFKIT SOUNDINGS SHOW STEEPER LOW LEVEL LAPSE RATES WITH
WEAK IMPULSE TRACKING INTO EASTERN WISCONSIN TUESDAY. ISOLATED
SHOWERS/THUNDERSTORMS WILL BE POSSIBLE MAINLY EAST OF THE
MISSISSIPPI RIVER...WITH SLIGHTLY HIGHER CHANCES OVER NORTH
CENTRAL WISCONSIN.

THE FORECAST AREA REGION REMAINS UNDER THE INFLUENCE OF THE UPPER
LEVEL TROUGH OVER THE EASTERN HALF OF THE UNITED STATES TUESDAY
NIGHT INTO SATURDAY. THE 27.00Z GFS/GEM/ECMWF CONTINUE TO SHOW
SEVERAL WEAK IMPULSES TO MOVE OVER THE AREA THROUGH THE PERIOD AND
POSSIBLY PRODUCE ISOLATED SHOWERS AND THUNDERSTORMS THROUGH MUCH
OF THE PERIOD. TEMPERATURES ARE EXPECTED TO REMAIN SLIGHTLY BELOW
NORMAL...AS THE 27.00Z GEFS INDICATE 850MB TEMPERATURE ANOMALIES
OF A HALF TO ONE DEGREE CELSIUS BELOW NORMAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1244 PM CDT SUN JUL 27 2014

UPPER SYSTEM DROPPING SOUTHEAST ACROSS WI AT MID-DAY WITH
EXTENSIVE WRAP AROUND CLOUD AND SHOWER ACTIVITY. AS THE LOW PULLS
OFF TO THE EAST AND BEST LIFT EXITS ALONG WITH IT...ANTICIPATE
SOME DOWNWARD MOTIONS TO HELP FLATTEN AND EVENTUALLY
THIN/DISSIPATE THE CLOUD COVER. MODEL MOS GUIDANCE VERY AGGRESSIVE
WITH THIS TREND...BUT AM LEARY OF THIS GIVEN THE AMOUNT OF
MOISTURE REMAINING IN THE BOUNDARY LAYER. PLAYED IT A BIT MORE
PESSIMISTIC FOR THE 18Z TAF ISSUANCE. DID GO WITH A PERIOD OF SCT
CLOUD COVER...BUT ONCE DIURNAL HEATING BEGINS AGAIN
TOMORROW...WENT BACK TO BKN.

&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...MW



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