Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 271141
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
641 AM CDT THU AUG 27 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 346 AM CDT THU AUG 27 2015

AT 3 AM...A MESOSCALE CONVECTIVE COMPLEX WAS MOVING EAST ACROSS
SOUTH DAKOTA. THIS SYSTEM WAS NOT HANDLED WELL BY THE
DETERMINISTIC NAM...GFS...AND ECMWF. MEANWHILE BOTH THE ARW AND
NMM BRING THIS SYSTEM INTO SOUTHEAST MINNESOTA THIS AFTERNOON.
THIS SEEMS A BIT TOO MUCH OVER DONE CONSIDERING THE DRY DEW POINTS
OVER THE AREA. THE HRRR ALSO MOVES THIS SYSTEM EAST AND WEAKENS IT
ACROSS MINNESOTA. HOWEVER SOME LINGERING SHOWERS AND STORMS
CONTINUE ALONG A BAND OF 700 TO 500 MB FRONTOGENESIS. WITH SO MUCH
UNCERTAINTY...OPTED TO GO MORE OF A BLEND THAT SOME OF THE SHOWERS
AND STORMS WOULD MOVE INTO THE FAR WESTERN COUNTIES OF THE COUNTY
WARNING AREA THIS AFTERNOON. HOWEVER DID NOT INCLUDE ANY
PRECIPITATION INTO CLARK AND TAYLOR COUNTIES AT THIS TIME.

FOR TONIGHT...THE NAM...GFS...AND ECMWF TRACK THE SURFACE LOW
NEAR THE MINNESOTA AND IOWA BORDER. WITH MUCH OF THE 950 TO
500 MB FRONTOGENESIS REMAINING ACROSS SOUTHERN MINNESOTA AND
NORTHERN IOWA OVERNIGHT KEPT THE HIGHEST RAIN CHANCES MAINLY WEST
OF THE MISSISSIPPI RIVER. WILL HAVE TO WATCH HOW CYCLOGENESIS
TAKES PLACE ACROSS NEBRASKA TODAY. THERE IS SOME SUGGESTION IN THE
MESO MODELS THAT THE STRONGER WAVE COMING OUT OF THE CENTRAL AND
NORTHERN PLAINS WILL BE LOCATED MUCH FURTHER SOUTH AS THE SHORT
WAVE EJECTS NORTHEAST OUT OF UTAH THIS MORNING. IF THIS SCENARIO
COMES TRUE...WE MAY BE TOO FAR NORTH WITH THE RAINFALL TONIGHT AND
FRIDAY.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 346 AM CDT THU AUG 27 2015

FROM FRIDAY INTO FRIDAY NIGHT...THE 27.00Z DETERMINISTIC
GFS...NAM...AND ECMWF CONTINUE TO SHOW STRONG 950 TO 500 MB
FRONTOGENESIS AND 925 TO 850 MB MOISTURE TRANSPORT ALONG AND
NORTH OF THE INTERSTATE 90 CORRIDOR. THIS OCCURS AS A SHORT WAVE
TROUGH LIFTS EAST NORTHEAST OUT OF NEBRASKA. DESPITE THE LACK OF A
INSTABILITY...PRECIPITABLE WATER VALUES RANGE AROUND 1.6 INCHES
AND WARM CLOUD LAYER DEPTHS RANGING BETWEEN 4 AND 4.5 KM...THERE
WILL BE COALESCENCE OF THE RAIN DROPLETS...THUS...HEAVY RAIN LOOKS
POSSIBLE. BOTH THE NAM AND GFS SUGGEST A BAND OF 3 TO 4 INCHES.
MEANWHILE THE ECMWF LOOKS MORE REASONABLE CONSIDERING THE
INSTABILITY WITH A 1 TO 3 INCH BAND.

WHILE THERE IS GREAT AGREEMENT AMONGST THESE MODELS...THERE IS
SOME CONCERN THAT THE SHORT WAVE CURRENTLY DEVELOPING ACROSS
SOUTHEAST UTAH MAY CAUSE THE SURFACE LOW TO TAKE A MUCH FURTHER
SOUTH TRACK ACROSS IOWA. THE ARW...NMM...GEM...AND 11 OF THE 12
GFS MEMBERS WOULD SUGGEST THAT THIS COULD BE A POSSIBILITY. IF
THIS SCENARIO DID COME TRUE...THAN THE RAIN BAND WOULD HAVE TO BE
SHIFTED MUCH FURTHER SOUTH WHICH WOULD BE GREAT FOR THE ABNORMALLY
DRY AND MODERATE DROUGHT AREAS OF SOUTHWEST WISCONSIN AND
NORTHEAST IOWA.

FOR THE TIME BEING...STAY WITH THE MORE CONSISTENT GFS...NAM...
AND ECMWF AND WILL WATCH TO SEE HOW THE CYCLOGENESIS DEVELOPS
ACROSS THE CENTRAL PLAINS TODAY.

FROM TUESDAY THROUGH WEDNESDAY...THE MODELS CONTINUE TO SHOW THAT
A STRONG RIDGE OF HIGH PRESSURE WILL BE LOCATED ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. WITH 925 MB TEMPERATURES RUNNING AROUND
26 TO 27C...HIGH TEMPERATURES IN THE RIVER VALLEYS WILL LIKELY
CLIMB INTO THE LOWER 90S...AND INTO THE MID TO UPPER 80S. SINCE
THIS HAS BEEN A VERY CONSISTENT SIGNAL...RAISED THE MODEL
CONSENSUS HIGH TEMPERATURES ON BOTH DAYS BY 3 TO 5 DEGREES IN THE
RIVER VALLEYS AND 2 DEGREES ELSEWHERE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 640 AM CDT THU AUG 27 2015

MORNING FOG WILL DISSIPATE AROUND THE KLSE AIRFIELD IN THE NEXT
HOUR OR SO. THEN VFR CONDITIONS ARE EXPECTED AS A WEATHER SYSTEM
MOVES TOWARD THE AIRFIELDS FOR FRIDAY. EXPECT CIGS/VSBYS TO BE
LOWERED TO AT LEAST MVFR FRIDAY...BUT TRENDS WILL LIKELY BE TOWARD
IFR IN SHRA/RA.

&&

.HYDROLOGY...TONIGHT THROUGH FRIDAY NIGHT
ISSUED AT 346 AM CDT THU AUG 27 2015

BOTH THE GFS AND NAM ARE SUGGESTING 3 TO 4 INCHES RAIN ALONG AND
NORTH OF THE INTERSTATE 90 CORRIDOR. MEANWHILE THE THE ECMWF HAS
1 TO 3 INCHES OF RAIN IN THIS SAME GENERAL LOCATION. CONSIDERING
THE AMOUNT OF INSTABILITY LOCATED AROUND THE AREA...THOUGHT THAT
THE ECMWF AMOUNTS SEEMED A BIT MORE REALISTIC...SO TRENDED THE
QPFS TOWARD IT. ELSEWHERE RAINFALL AMOUNTS LOOK TO BE LESS THAN
AN INCH.

HOWEVER AS STATED IN THE LONG TERM SECTION WILL HAVE TO
WATCH HOW THIS HEAVY RAINFALL BAND DEVELOPS TONIGHT...BECAUSE 11
OF 12 OF GFS FAMILY MEMBERS...GEM...ARW...AND NMM HAVE THE
HEAVIEST QPF BAND SOUTH OF THE INTERSTATE 90 CORRIDOR WHICH WOULD
BE GREAT FOR THE ABNORMALLY DRY AND DROUGHT AREAS OF NORTHEAST
IOWA AND SOUTHWEST WISCONSIN.

WITH HOURLY RAIN RATES LESS THAN AN INCH AN HOUR...NOT ANTICIPATING
ANY ISSUES WITH URBANIZED FLOODING. IN ADDITION...AREA RIVERS AND
STREAMS HAVE FLOWS CURRENTLY RUNNING ANYWHERE FROM 25 TO 50 PERCENT
OF CLIMATOLOGY. AS A RESULT...THIS RAIN SHOULD ONLY RESULT IN BANK
RISES.

&&

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

$$

SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...BAUMGARDT
HYDROLOGY...BOYNE


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