Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 270824
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
324 AM CDT WED APR 27 2016

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 324 AM CDT WED APR 27 2016

MAIN CONCERN TODAY IS THE ONSET OF RAIN AS THE LARGE COMPLEX
APPROACHES FROM THE SOUTHWEST. DRY EASTERLY FLOW AHEAD OF IT IS
SLOWING THE EASTWARD PROGRESS...AND MODEL TRENDS HAVE ALSO SLOWED
THE PROGRESSION. MOST OF THE FORECAST TWEAKS THIS MORNING HAVE
RELATED TO SLOWING DOWN WHEN THE RAIN WILL START...AND HOW FAR
NORTH IT EVENTUALLY GETS BEFORE STALLING OUT. LOOKING AT A PLETHORA
OF SHORT RANGE MESO MODELS...THE EARLIEST THE RAIN REACHES THE FAR
SOUTHWEST COUNTIES OF OUR SERVICE AREA IS BETWEEN 16-18Z. IT WILL BE
AFTERNOON BEFORE THE RAIN BEGINS TO IMPACT THE MAJORITY OF THE LOCAL
AREA...AND CLOSER TO SUNSET BEFORE IT REACHES OUR FAR NORTHERN
EXTENT. THE STRONGEST FORCING AND INSTABILITY REMAINS CONFINED WELL
TO OUR SOUTH...SO THE RISK FOR ANY THUNDER IS TOO LOW TO WARRANT A
MENTION. BUT THE FRONTOGENETIC AND ISENTROPIC FOCUS IS RATHER
GOOD...AND ANTICIPATE THAT BANDS OF RAIN WILL DEVELOP AND REMAIN
QUASI-STATIONARY IN THE VICINITY OF THE I-90 CORRIDOR LATER TODAY.
CONVECTION TO THE SOUTH WILL LIKELY STEAL MUCH OF THE MOST
SIGNIFICANT MOISTURE SUPPLY...BUT AMOUNTS BETWEEN 0.50 AND 1.00
INCHES LOOK LIKE A GOOD BET FROM NORTHEAST IOWA AND SOUTHWEST
WISCONSIN...INTO ADJACENT PORTIONS OF SOUTHEAST MINNESOTA. RAIN
WILL CONTINUE THROUGH TONIGHT AND INTO THURSDAY BEFORE TAPERING OFF
BY EVENING.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 324 AM CDT WED APR 27 2016

AREA WILL BE BETWEEN SYSTEMS ON FRIDAY WITH BRIEF RIDGING PROVIDING
FOR A DRY DAY. WE SHOULD SEE SOME SUN AS WELL...SO DESPITE COOL
NORTH TO NORTHEAST FLOW...HIGHS SHOULD APPROACH 60 DEGREES. BUT THE
NEXT IN A PARADE OF CLOSED SYSTEMS IS ALREADY PLOWING THROUGH THE
DESERT SOUTHWEST BY THIS TIME...AND IT WILL MOVE TOWARD OUR AREA FOR
THE WEEKEND. THE OVERALL SETUP IS NEARLY IDENTICAL...WITH A LARGE
RAIN SHIELD SPREADING OUT AHEAD OF IT. AND ONCE AGAIN THE ONSET WILL
BE PROBLEMATIC WITH DRY EASTERLY FLOW AHEAD OF THE APPROACHING RAIN.
BUT THE MODELS HAVE BEEN SHOWING MORE DIVERGING SIGNALS IN THE MOST
RECENT RUNS. PREVIOUSLY...A WEAKENING CLOSED LOW WAS EXPECTED TO
MOVE ACROSS THE REGION THROUGH THE WEEKEND PROVIDING RAINY AND COOL
WEATHER. BUT THERE ARE SOME INDICATIONS NOW THAT THE MAIN
CIRCULATION MAY RETROGRADE BACK INTO THE TROUGH AS A LARGER PIECE
OF ENERGY DIGS INTO THE BACK SIDE. IF THIS OCCURS...WE MAY NOT SEE
MUCH RAIN AT ALL...SO WE WILL HAVE TO MONITOR THIS. FOR NOW DID
LOWER THE RAIN CHANCES...BUT DID NOT REMOVE THEM YET WITH THE
UNCERTAINTY. IT IS LOOKING LIKE A PATTERN SHIFT WILL TAKE PLACE BY
THE MIDDLE OF NEXT WEEK...WITH A MORE HIGHLY AMPLIFIED FLOW REGIME.
THIS LEADS TO THE POSSIBILITY OF A LARGE HUDSON BAY LOW TO DROP INTO
THE GREAT LAKES REGION...LEADING TO A COOL PERIOD. TIME WILL TELL...

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1133 PM CDT TUE APR 26 2016

DRIER AIR WORKING IN FROM THE EAST AND NORTHEAST HAS BEEN CHIPPING
AWAY AT MVFR CEILINGS...AND WOULD EXPECT THIS TO CONTINUE OVERNIGHT.
AT THE SAME TIME MID/HIGH LEVEL CLOUDS CONTINUE TO INCREASE FROM THE
SOUTHWEST AHEAD OF LARGE STORM SYSTEM OVER CENTRAL STATES.

AS UPPER / SURFACE LOW CREEP CLOSER NEXT 24 HOURS...EXPECT
SATURATION TO RETURN AS BAND OF SHOWERS WORKS NORTHEASTWARD
WEDNESDAY. TIMING HAS BEEN SLOWING BUT MID AFTERNOON TIME FRAME AT
TAF SITES STILL SEEMS REASONABLE. WILL PLAY A MORE PESSIMISTIC AND
STEADY PRECIPITATION THREAT INSTEAD OF OCCASIONAL IN NEW FORECASTS
WITH IFR TO MVFR CONDITIONS LIKELY RETURNING WEDNESDAY NIGHT.


&&

.HYDROLOGY...
ISSUED AT 324 AM CDT WED APR 27 2016

SIGNIFICANT RAINFALL OVER THE PAST SEVERAL DAYS UPSTREAM OF THE
REGION WILL PRODUCE RISES ON THE MISSISSIPPI RIVER OVER THE NEXT FEW
WEEKS. CURRENT PROJECTIONS SUGGEST THE RIVER WILL BE RISING TO
WITHIN 2-4 FEET OF FLOOD STAGE BY EARLY MAY. THOSE WITH INTERESTS
ALONG THE RIVER SHOULD MAKE PREPARATIONS FOR HIGHER WATER LEVELS
EARLY MAY.

&&

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

$$

SHORT TERM...MW
LONG TERM...MW
AVIATION...SHEA
HYDROLOGY...MW



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