Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 041117
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
617 AM CDT SAT JUL 4 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 230 AM CDT SAT JUL 4 2015

WEAK FRONTAL BOUNDARY RESPONSIBLE FOR THE LATE DAY CONVECTION OVER
NORTHERN WI YESTERDAY WILL SINK SOUTHWARD ACROSS THE FORECAST AREA
TODAY. MESO MODELS DON/T APPEAR AS ENTHUSIASTIC IN THE SOUTHERN PUSH
OF THE BOUNDARY...LEANING TOWARD KEEPING IT NORTH OF I-90. ISOLATED
CONVECTION SPARKS AS AFTERNOON INSTABILITY BUILDS...CONTINUING INTO
THE EVENING. I-94 CORRIDOR AND NORTH LOOKS TO BE A BIT MORE FAVORED
FOR THIS WIDELY SCATTERED ACTIVITY. IT WON/T BE A RAIN OUT FOR
ANYONE/S 4TH OF JULY PLANS...BUT CAN/T RULE OUT A FEW PEOPLE GETTING
WET - ALTHOUGH THE VAST MAJORITY WILL STAY DRY.

THE SMOKE FROM FIRES ACROSS ALASKA AND CANADA ARE MAKING FOR
SPECTACULAR SUNRISE/SUNSETS...ALONG WITH GIVING THE MOON A RED HUE.
ITS MAY ALSO SERVE TO TEMPER HIGH TEMPS A FEW DEGREES...CUTTING OFF
SOME OF THE SUN. THAT SAID...A PUSH OF LOW LEVEL WARM AIR ADVECTION
AND A MORE SOUTHERLY SFC/NEAR SFC FLOW SHOULD HELP TEMPS WARM WELL
INTO THE 80S. LIKELY AT OR ABOVE THE SEASONABLE NORMALS. MAY TICK
THEM BACK A DEGREE OR TWO ON ACCOUNT OF THE SMOKE.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 230 AM CDT SAT JUL 4 2015

NAM/GFS/ECMWF/GEM ALL IN GOOD AGREEMENT WITH DRIVING AN UPPER LEVEL
TROUGH FROM WESTERN CANADA SOUTHWEST...MOVING OVER THE NORTHERN
PLAINS BY 12Z MON...AND EAST OVER THE NORTHERN GREAT LAKES BY 00Z
TUE. THE BULK OF THE UPPER LEVEL FORCING WITH THE TROUGH HOLDS NORTH
OF THE LOCAL AREA...BUT ITS ASSOCIATED SFC COLD FRONT WILL TRACK
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY...RUNNING FROM NORTHWEST
WI INTO WESTERN IA BY 18Z MON...AND GRADUALLY TREKKING INTO EASTERN
WI LATER MON EVENING. GOOD FRONTOGENETIC LIFT WITH THE
BOUNDARY...ALONG WITH A SLUG OF LOW LEVEL WARMING. RIGHT ENTRANCE
REGION OF THE 300 MB COULD ADD SOME ADDITIONAL LIFT AS THE SYSTEM
MOVES THROUGH. APPRECIABLE SLUG OF 850 MB MOISTURE TRANSPORT DRIVING
ALONG AND AHEAD OF THE FRONT SUN NIGHT...HOLDING STEADY AHEAD OF IT
AS THE SYSTEM MOVES EAST ON MONDAY. PLENTY OF LIFT AND MOISTURE FOR
AREAS/LINE OF SHOWERS AND THUNDERSTORMS MONDAY-MONDAY NIGHT.

THE MODELS HAVE GENERALLY FAVORED DEVELOPING MUCH OF THE PCPN ALONG
AND POST THE FRONT...WITH A 900-800 MB WARM LAYER ACTING AS A CAP TO
SFC BASED CONVECTION AHEAD OF IT. NEED THE KICK OF THE BOUNDARY TO
GET THINGS GOING.

INSTABILITY BUILDS AHEAD OF THE FRONT...UPWARDS OF 2000 J/KG OF
MUCAPE VIA THE GFS. THE NAM REMAINS MORE ROBUST...PUSHING 3500
J/KG...AND LIKELY OVERDONE. SOME UNCERTAINTY TO HOW MUCH CLOUD COVER
AS THE FRONT APPROACHES...WHICH WOULD BE A LIMITING FACTOR TO HOW
MUCH INSTABILITY COULD BE REALIZED. THE BULK OF THE WIND SHEAR IS
WELL BEHIND THE FRONT...WITH THIS DISCONNECT BETWEEN INSTABILITY-
SHEAR SERVING TO LIMIT THE SEVERE THREAT. HOWEVER...THE THREAT FOR
HEAVY RAIN IS HIGH. FOR MORE DETAILS ON THE RAIN THREAT...CONSULT
THE HYDROLOGY SECTION BELOW. SUFFICE TO SAY...WHILE THE TIMING OF
THE SYSTEM MAY LIMIT THE POTENTIAL FOR BIG HAIL/WIND...THE HAZARDS
FROM HEAVY RAIN ARE PEAKING. THANKFULLY GROUNDS ARE NOT SATURATED
OTHERWISE A FLASH FLOOD WATCH WOULD BE A GIMMIE.

MODELS STAY IN DECENT AGREEMENT FOR THE REST OF THE WEEK...GOING
FROM ZONAL FLOW TO A BIT MORE UPPER LEVEL RIDGING TOWARD NEXT
WEEKEND. ALL SUGGEST ANY SIGNIFICANT - EVEN SMALL - SHORTWAVE
TROUGHS WOULD SHUFFLE NORTH OR SOUTH OF THE LOCAL FORECAST
AREA...MAKING DRY CONDITIONS LIKELY THROUGH THE REST OF THE WORK
WEEK. SOME POTENTIAL FOR A SHORTWAVE TO THEN SWING ACROSS THE REGION
SAT/SUN...RETURNING THE THREAT FOR RAIN. WILL HOLD WITH CONSENSUS
RAIN CHANCES.

TEMPS LOOK TO BE A FEW DEGREES BELOW THE EARLY JULY NORMS AFTER THE
FRONTAL PASSAGE ON MONDAY...BUT THE RIDGE WOULD ALLOW FOR WARMING BY
THE WEEKEND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 617 AM CDT SAT JUL 4 2015

INITIALLY WILL BE DEALING WITH STRATUS AND AREAS OF FOG IN THE
MISSISSIPPI RIVER VALLEY WHICH WILL IMPACT KLSE THIS MORNING.
LOOK FOR TEMPO LIFR CONDITIONS THROUGH 13Z...BURNING OFF SHORTLY
THEREAFTER.

FOR THE REST OF THE PERIOD...LOOK FOR GENERALLY HAZY CONDITIONS TODAY
AS CANADIAN WILDFIRES CONTINUE TO SEND SMOKE PARTICULATES OUR
WAY. THESE PARTICULATES LOOK TO PARTIALLY MIX WITH BOUNDARY LAYER
MOISTURE FOR WIDESPREAD 3-5SM HZ. SOME IMPROVEMENT LOOKS TO OCCUR
AFTER MIDNIGHT AS BOUNDARY LAYER WINDS INCREASE OUT OF THE
SOUTH...TAKING THESE HAZY CONDITIONS NORTH OF THE AREA.

&&

.HYDROLOGY...(MONDAY AND MONDAY NIGHT)
ISSUED AT 230 AM CDT SAT JUL 4 2015

BOTH THE GFS AND NAM POINT TO WARM CLOUD DEPTHS OF 4000+ M WITH PWS
APPROACHING 2 1/4 INCHES MONDAY. PW ANOMALIES ARE 2-3 VIA NAEFS. ANY
STORMS/SHOWERS SHOULD BE VERY EFFICIENT RAIN PRODUCERS...WITH
COPIOUS AMOUNTS LOOKING LIKELY. IF REALIZED...EXPECT LOCALIZED/
URBAN FLOODING...WHICH COULD LEAD TO MORE EXTENSIVE PROBLEMS IF
THERE IS TRAINING OR REPEATED HITS ON LOCATIONS. 3 HOUR FFG SITS AT
2.5-3 FOR THE MOST PART. IF THE GROUNDS WERE SATURATED...WOULD HAVE
TO HOIST A FLASH FLOOD WATCH. DEFINITELY SOMETHING TO WATCH.

&&

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

$$

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


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