Area Forecast Discussion
Issued by NWS La Crosse, WI

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418
FXUS63 KARX 261711
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1211 PM CDT TUE APR 26 2016

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 306 AM CDT TUE APR 26 2016

INITIAL CONCERN IS WITH CLOUD COVER...FOG AND PATCHY DRIZZLE THIS
MORNING. FOCUS THEN SHIFTS TO CLOUD TRENDS TODAY INTO TONIGHT...AND
THE ONSET OF RAIN CHANCES OVERNIGHT.

07Z ANALYSIS SHOWING THE MAIN SYSTEM FROM THE PAST SEVERAL DAYS HAS
WEAKENED AND SHIFTED EAST INTO THE GREAT LAKES. BUT A DIURNAL
NORTHEAST FLOW AND AMPLE BOUNDARY LAYER MOISTURE IN ITS WAKE IS
RESULTING IN WIDESPREAD LOW CLOUD AND SOME PATCHY LIGHT RAIN OR
DRIZZLE. THIS MAY LINGER FOR A TIME THIS MORNING UNTIL THE BUILDING
UPPER RIDGE CAN HELP TO SHIFT THE BOUNDARY LAYER MOISTURE BACK NORTH
AGAIN. BUT ANY POTENTIAL CLEARING LATER TODAY WILL BE SHORT-LIVED AS
ADVANCING AND THICKENING CLOUD COVER WILL AGAIN BUILD IN FROM THE
SOUTHWEST AS THE NEXT CLOSED CIRCULATION CURRENTLY OVER THE DESERT
SOUTHWEST BEGINS TO EJECT NORTHEAST TOWARD THE UPPER MIDWEST. MODEL
TRENDS WITH THIS HAVE BEEN SLOWER WITH TIME...WHICH MAKES SENSE
GIVEN THE CLOSED CIRCULATION. HAVE SLOWED THE PRECIPITATION ONSET
SOMEWHAT WITH THIS UPDATE...AND IT MAY NEED TO BE SLOWED EVEN
FURTHER IF TRENDS CONTINUE.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 306 AM CDT TUE APR 26 2016

UPPER SYSTEM FINALLY MAKES IT TO THE AREA ON WEDNESDAY. RAIN WILL
SLOWLY SPREAD NORTH AND EAST INTO THE REGION AS THE DAY WEARS ON.
EASTWARD ADVANCE WILL BE SLOWED BY DRY EASTERLY FLOW...BUT EXPECT IT
TO OVERSPREAD THE FORECAST AREA BY WEDNESDAY NIGHT. COULD BE A FEW
RUMBLES OF THUNDER IN THERE...BUT WITH LIMITED INSTABILITY APPEARS
IT WILL BE ISOLATED AT BEST. SIMILAR TO THE LAST SYSTEM...THIS ONE
LOOKS TO SLOWLY FILL AND SHEAR OUT FROM THURSDAY INTO FRIDAY. BUT
THE POSITION IS ACROSS IA/MO/IL INSTEAD...WHICH KEEPS THE LOCAL AREA
MORE IN THE FRONTOGENETIC/ISENTROPIC UPGLIDE REGION IN THE
DEFORMATION AXIS NORTH OF THE SYSTEM. THERE IS THE POTENTIAL FOR
SOME EFFICIENT RAIN PRODUCTION...AND CONCERNED THE MODEL QPF MAY BE
UNDERPLAYED. WILL HAVE TO WATCH THIS TREND IN LATER FORECASTS.
SYSTEM LOOKS TO FINALLY WEAKEN AND SHIFT CLEAR OF THE LOCAL AREA BY
FRIDAY.

WITH PLENTY OF CLOUDS AND WET WEATHER...TEMPERATURES LOOK TO BE ON
THE COOL SIDE FOR THE REMAINDER OF THE WEEK. IN FACT...OVERNIGHT
TEMPERATURES MAY BE COOL ENOUGH OVER THE FAR NORTHEAST PORTION OF
THE FORECAST AREA TO SEE A MIX WITH SOME SNOW WEDNESDAY NIGHT.

LOOKS LIKE WE DRY OUT FOR FRIDAY...BUT THE NEXT SLOW-MOVING CLOSED
CIRCULATION WILL BE HEADING INTO THE AREA FOR THE WEEKEND AS THE
HIGHLY AMPLIFIED BUT BLOCKY PATTERN CONTINUES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 1211 PM CDT TUE APR 26 2016

LOW CLOUD DECKS SLOWLY LIFTING FROM IFR TO MVFR LATE THIS MORNING
WITH SLOW DIURNAL WARMING AND AN INFLUX OF DRIER BOUNDARY LAYER AIR
ON THE EAST-NORTHEAST FLOW. HOWEVER...AREA PIREPS FROM THIS MORNING
SHOWING THE CLOUD DECK SOME 2K-3K FT THICK. 26.12Z RAOBS FROM KMPX/
KGRB SHOWING THE DEEPER CLOUD DECK MOISTURE AS WELL...ALONG WITH
MUCH OF THIS MOISTURE TRAPPED IN/UNDER AN INVERSION AROUND 900MB.
ALL THIS POINTS TO THE LOWER CLOUDS BEING VERY PERSISTENT ACROSS THE
TAF SITES INTO THIS EVENING. CIGS TO GRADUALLY RISE THRU THE
AFTERNOON/EARLY EVENING...THEN BECOME SCT IN THE 03Z-04Z TIME-FRAME
AS THE DRIER EASTERLY SFC-900MB FLOW EVENTUALLY WINS OUT. REMAINDER
OF THE TAF PERIOD THEN EXPECTED TO BE VFR. MOISTURE SPREADING
NORTHEAST WITH THE SYSTEM MOVING TOWARD THE REGION FROM THE PLAINS
IS MAINLY MID LEVEL...WITH CIGS AOA 7K FT LATER TONIGHT/WED MORNING.
DEEPER SATURATION AND THE RAIN CHANCES LOOKING TO SPREAD INTO THE
KRST AREA 18-20Z WED AFTERNOON THEN INTO KLSE AFTER 27.21Z.

&&

.HYDROLOGY...
ISSUED AT 306 AM CDT TUE APR 26 2016

THE SIGNIFICANT RAINFALL OVER THE PAST FEW DAYS UPSTREAM OF THE
REGION LOOKS TO SEND THE MISSISSIPPI RIVER BACK ON AN UPWARD TREND
OVER THE NEXT FEW WEEKS. CURRENT PROJECTIONS SUGGEST THE RIVER WILL
BE RISING TO WITHIN 2-4 FEET OF FLOOD STAGE BY EARLY MAY. SO THOSE
WITH INTERESTS ALONG THE RIVER SHOULD MAKE PREPARATIONS FOR HIGHER
WATER LEVELS IN THE COMING WEEKS.

&&

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

$$

SHORT TERM...MW
LONG TERM....MW
AVIATION.....RRS
HYDROLOGY....MW



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