Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261918
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
215 PM CDT FRI JUN 26 2015

.SHORT TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 215 PM CDT FRI JUN 26 2015

CONVECTION FIRING IN A BROAD REGION OF UNSTABLE AIR...JUST NEEDING A
FOCUS TO GET IT GOING. LATEST RADAR IMAGERY PLACES ONE CLUSTER
DIVING SOUTH ACROSS CENTRAL MN IS TIED TO A BIT OF UPPER LEVEL
ENERGY. OVER IA INTO NORTHERN ILL IS CO-LOCATED WITH THE BASE OF THE
UPPER LEVEL TROUGH. ELSEWHERE...ENHANCED CU AND SOME ISOLATED
SHOWERS WERE THE RULE. HEADING INTO THE EVENING...EXPECT BOTH AREAS
OF PCPN TO CONTINUE - DYING OUT WITH THE LOSS OF THE DAYTIME
HEATING. BUT...THE RAP AND NAM12 SUGGEST A SOUTHWEST-NORTHEAST
RUNNING BOUNDARY ACROSS THE FORECAST AREA...WHICH COULD SERVE AS A
TRIGGER FOR A SCATTERED LINE OF SHOWERS/STORMS LATE AFTERNOON/EARLY
EVENING. WILL MONITOR AND INCREASE POPS IF THIS BECOMES LIKELY.

UPPER LEVEL SHORTWAVE TROUGH SLATED TO MOVE ACROSS THE AMPLIFIED
RIDGE OVER THE WEST...SPINNING ACROSS THE UPPER MISSISSIPPI RIVER
VALLEY ON SUNDAY. DECENT QG CONVERGENCE WITH THIS FEATURE...ALONG
WITH LOW LEVEL WARMING - ALTHOUGH MOSTLY CENTERED OVER IA. 300 MB
JET STREAK LOOKS TO ENHANCE THE LIFT. PLENTY OF DYNAMICS AND ENOUGH
SATURATION FOR AN AREA OF SHOWERS AND THUNDERSTORMS...AND ALL THE
MODELS HAVE SAID AS MUCH OVER THE PAST FEW DAYS.

QUESTIONS ARISE WITH THE TIMING OF THE SHORTWAVE/AREAS OF RAIN AND
HOW MUCH INSTABILITY/SHEAR WILL BE PRESENT. 12Z GFS/NAM RUNS BRING
THE SHORTWAVE IN BY 12Z SUN...WITH PCPN LIKELY FOR AT LEAST THE
WESTERN 1/2 OF THE FORECAST AREA BY THAT TIME. THE PCPN AND TROUGH
AXIS THEN SWINGS INTO WESTERN WI FOR SUN AFTERNOON. NOT A LOT OF
SHEAR THROUGH THE DAY...MOST OF WHICH LIES IN THE 0-3KM LAYER -
ROUGHLY 20-30 KTS. AS ONE WOULD EXPECT...NOT MUCH INSTABILITY AT 12Z
SUN MORNING...BUT THE GFS/NAM DEVELOP A RIBBON OF 1500-2000 J/KG
SBCAPE ACROSS THE WESTERN 2/3RDS OF THE FORECAST AREA IN THE
AFTERNOON. HOWEVER...THIS IS POST THE PCPN SHIELD AND MUCH OF THE
DYNAMICS. NOT SURE IT WILL/COULD BE UTILIZED BY THE EXPECTED ONGOING
CONVECTION...OR FOR ANY REDEVELOPMENT IN THE WEST. AS A
RESULT...BELIEVE THE POTENTIAL FOR ORGANIZED SEVERE WEATHER IS
LOW...ALTHOUGH A FEW STRONGER STORMS COULD BE POSSIBLE. ALL IN
ALL...SUNDAY LOOKS LIKE A WET DAY...WEST OF THE MISSISSIPPI RIVER IN
THE MORNING...EAST IN THE AFTERNOON.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 215 PM CDT FRI JUN 26 2015

AFTER SUNDAY...THE GFS/ECMWF HOLD ONTO THE WESTERN RIDGE-EASTERN
TROUGH CONFIGURATION FOR MUCH OF THE NEW WEEK...KEEPING THE LOCAL
AREA UNDER NORTHWEST FLOW. VARIOUS PERTURBATIONS IN THE UPPER LEVEL
LEVEL FLOW WOULD SPIN ACROSS THE UPPER MISSISSIPPI RIVER
VALLEY...RESULTING IN PERIODIC RAIN CHANCES. MODEL DIFFERENCES IN
PLACEMENT AND TIMING OF THESE BITS OF ENERGY - AS EXPECTED - BUT
NONE OF THE SOLUTIONS ARE SUGGESTIVE OF WIDESPREAD...ALL-DAY KIND OF
RAIN EVENTS. INSTABILITY AND WIND SHEAR DON/T FAVOR ORGANIZED SEVERE
WEATHER AT THIS TIME EITHER. WILL CONTINUE THE BLANKET OF SMALL RAIN
CHANCES THROUGH THE PERIOD...REVISING AS THE DETAILS BECOMING
CLEARER.

WITH THE RELATIVELY COOLER NORTHWEST TRAJECTORY COUPLED WITH
CLOUDS/RAIN POTENTIAL...TEMPERATURES SHOULD HOLD NEAR OR BELOW THE
SEASONABLE NORMALS. IN ADDITION...NO TO LIMITED TAP INTO GULF
MOISTURE DURING THE WEEK SHOULD KEEP HUMIDITIES IN CHECK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1254 PM CDT FRI JUN 26 2015

ISOLATED SHOWERS ARE DEVELOPING ALONG A WEAK AREA OF CONVERGENCE
ACROSS SOUTHEAST MINNESOTA. DUE TO THIS...INCLUDED SHOWERS IN THE
TEMPO GROUP AT KRST THROUGH 26.20Z. OTHERWISE...THERE WILL BE A
SCATTERED TO BROKEN 3-5K DECK OF CLOUDS THROUGH 27.05Z AND THEN
SKIES WILL CLEAR. WINDS WILL BE INITIALLY BE NORTHEAST AND THEN
SHIFT TO NORTH AFTER 27.05Z. WIND SPEEDS WILL BE LESS THAN 10 KNOTS.

WITH LIGHT WINDS TONIGHT AND SCATTERED SHOWERS THROUGH THIS
EVENING...WILL HAVE TO WATCH FOR THE POTENTIAL OF FOG...BUT WITH
UNCERTAINTY ON WHERE THESE SHOWERS WILL OCCUR...DID NOT INCLUDE IT
IN THE TAFS AT THIS TIME.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION.....BOYNE



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