Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 051113
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
613 AM CDT SUN JUL 5 2015

.SHORT TERM...(TODAY THROUGH MONDAY NIGHT)
ISSUED AT 315 AM CDT SUN JUL 5 2015

SHOWERS AND STORMS FOR MONDAY - WITH THE SUITE OF MODELS REMAINING
ADAMANT ITS GOING TO BE A WET START TO THE NEW WEEK. QUESTIONS ARE
WHETHER THERE COULD BE STRONG TO POSSIBLY SEVERE STORMS...AND JUST
HOW GOOD IS THE HEAVY RAIN POTENTIAL.

UPPER LEVEL TROUGH SLATED TO MOVE EAST ALONG THE US/CANADIAN
BORDER...MOVING ACROSS THE NORTHERN GREAT LAKES MONDAY EVENING. THE
BULK OF THE UPPER LEVEL FORCING HOLDS HERE...BUT ITS ACCOMPANYING
SFC COLD FRONT WILL DRIVE ACROSS THE UPPER MISSISSIPPI RIVER VALLEY
MON/MON NIGHT. DECENT MODEL CONSENSUS WITH LAYING THE BOUNDARY FROM
NORTHEAST WI INTO EASTERN IA AT 00Z TUE. GOOD FRONTOGENETIC RESPONSE
WITH THE FRONT...WHILE LOW LEVEL WARMING LEADS THE SYSTEM INTO THE
REGION. THIS WARMING SHOULD ACT AS A CAP TO CONVECTION...WITH MODELS
SUGGESTING STORMS WILL NEED THE LIFT AROUND THE FRONT TO GET
GOING...THUS MOST OF THE PCPN FALLS ALONG AND POST THE BOUNDARY.
HEFTY 850 MB MOISTURE TRANSPORT AHEAD OF THE FRONT...BECOMING MORE
FOCUSED TO THE NORTH BY MONDAY AFTERNOON. SO - EXPECT A LINE OF
SHOWERS/STORMS TO MARCH ACROSS THE REGION LATE TONIGHT-MONDAY...IN A
NE/SW ORIENTATION...BULK OF WHICH EXITS BY 06Z TUE.

AS FOR A STRONG/SEVERE THREAT...THE GFS/NAM BOTH BUILD A 2-3 K J/KG
RIDGE OF MUCAPE AHEAD OF THE FRONT...WITH THE NAM STILL A BIT MORE
AGGRESSIVE WITH THE INSTABILITY COMPARED TO THE GFS. DISCONNECT
PERSISTS WITH THE STRONGER/DEEPER WIND SHEAR - WHICH STAYS WELL
BEHIND THE FRONT. THE LIMITED / IF ANY OVERLAP HELPS TEMPER THE
SEVERE THREAT. MEANWHILE...DEEP WARM CLOUD DEPTHS IN EXCESS OF 4000
M ARE SUGGESTED...FAVORING HEAVY RAIN OVER LARGE HAIL. THAT SAID - A
LOT OF SMALL HAIL COULD OCCUR. THINK SOME STRONGER STORMS ARE
POSSIBLE...AND WON/T RULE OUT ISOLATED SEVERE. HEAVY RAIN AND STRONG
WINDS LOOK TO BE THE MAIN THREATS. FOR MORE ON THE HEAVY
RAIN POTENTIAL...CONSULT THE HYDROLOGY SECTION BELOW.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 315 AM CDT SUN JUL 5 2015

HIGH PRESSURE BUILDS IN TUESDAY...BRINGING A FEW DRY AND RELATIVELY
COOLER DAYS. OVERALL FLOW IS MORE ZONAL...BUT THE MODELS SUGGEST
BROAD RIDGING BY THE WEEKEND. WOULD GET A BUMP BACK TO THE
SEASONABLE NORMALS IF THIS OCCURS.

SOME DISCORD IN THE MODELS - EC/GFS/GEM - ON IF/WHEN ANY SHORTWAVES
ALONG THE FLOW WILL SKIP ACROSS THE FORECAST AREA...BRINGING A
SHOWER/STORM THREAT. LATEST GFS/GEM WOULD SWING A PERTURBATION
THROUGH THE PLAINS TO ACROSS THE LOCAL AREA ON FRIDAY. THE EC IS
WEAKER AND FARTHER SOUTH. NOT A CLEAR CUT WINNER HERE. WILL LEAN ON
CONSENSUS FOR RAIN CHANCES FOR NOW.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 613 AM CDT SUN JUL 5 2015

VFR CONDITIONS EXPECTED TODAY WITH BREEZY SOUTH WINDS. A COLD
FRONT WITH SHOWERS AND THUNDERSTORMS WILL THEN BE APPROACHING THE
UPPER MISSISSIPPI RIVER REGION OVERNIGHT...REACHING KRST BY 10Z
AND KLSE AFTER 12Z. PLAN ON SOME LOCALIZED HEAVY
DOWNPOURS/RAINFALL WITH THESE STORMS WHICH COULD DRASTICALLY
REDUCE VSBY AT TIMES. IN ADDITION...KLSE WILL LIKELY SEE LOW
LEVEL WIND SHEAR IN THE 10-12Z TIMEFRAME WITH WINDS AROUND 1.5KFT
OUT OF THE SOUTH/SOUTHWEST IN THE 40-45KT RANGE.

&&

.HYDROLOGY...(MONDAY THROUGH MONDAY NIGHT)
ISSUED AT 315 AM CDT SUN JUL 5 2015

IMPRESSIVE SIGNALS IN THE MODELS FOR HEAVY RAIN POTENTIAL - PWS IN
EXCESS OF 2 INCHES...WARM CLOUD DEPTHS OF 4000+ M...STRONG SURGE OF
850 MB MOISTURE TRANSPORT...AND NAEFS PW ANOMALIES RIGHT AROUND +3.
ANY STORM SHOULD BE A VERY EFFICIENT RAIN PRODUCER...AND COULD DROP
A CONSIDERABLE AMOUNT IN A VERY SHORT PERIOD OF TIME. MODELS HAVE
SHIFTED THE HEAVIEST RAIN TO THE NORTH...ON THE NOSE OF THE LOW
LEVEL JET AND WHERE THE STRONGEST UPPER LEVEL LIFT RESIDES.
ALSO...WITH A NORTHEAST-SOUTHWEST ORIENTATION...THE POTENTIAL FOR
TRAINING STORMS IS LOWERED...HELPING TO REIGN IN HIGHER QPF. ALL
SAID THOUGH...THE SETUP FAVORS LOCALIZED 2 INCH AMOUNTS.
MEANWHILE...RAINFALL RATES COULD RESULT IN URBANIZED FLOODING. A
FLASH FLOOD WATCH ISN/T NECESSARY...BUT THE SCENARIO WILL HAVE TO BE
MONITORED CLOSELY.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...DAS
HYDROLOGY....RIECK


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