666
FXUS63 KARX 161728
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1228 PM CDT WED OCT 16 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 328 AM CDT WED OCT 16 2013
MAIN FORECAST CONCERNS FOR TODAY ARE ON LINGERING DRIZZLE/LIGHT RAIN
AND CLOUD TRENDS THIS AFTERNOON. FOCUS THEN TURNS TO TEMPERATURES
AND PRECIPITATION CHANCES THURSDAY THROUGH THE WEEKEND.
LATEST WATER VAPOR IMAGERY SHOWED AN ELONGATED TROUGH STRETCHING
FROM CENTRAL ONTARIO SOUTHWEST THROUGH THE UPPER MISSISSIPPI RIVER
VALLEY THROUGH NEBRASKA INTO THE FOUR CORNERS REGION. TWO MAIN
EMBEDDED FEATURES TO KEY IN ON...ONE WEAKENING UPPER LOW OVER
NORTHERN WISCONSIN AND ANOTHER WEAK UPPER LOW NEAR THE FOUR CORNERS
REGION. SURFACE OBSERVATIONS SHOWED A SURFACE LOW LOCATED OVER
EASTERN UPPER MICHIGAN WITH A TROUGH EXTENDING SOUTHWEST OVER
CENTRAL WISCONSIN ALL THE WAY INTO WESTERN IOWA.
LOW CLOUDS AND DRIZZLE WILL LINGER OVER THE FORECAST AREA THIS
MORNING AS THE SURFACE TROUGH MEANDERS EAST. CLOUDS WILL LINGER INTO
THIS AFTERNOON BEFORE SURFACE RIDGING FINALLY BUILDS IN BY MID
AFTERNOON WITH CLOUDS GRADUALLY DECREASING FROM WEST TO EAST DURING
THE MID TO LATE AFTERNOON HOURS. WILL HAVE TO KEEP A CLOSE EYE ON
CLOUD TRENDS TODAY AS THEY WILL HAVE AN IMPACT ON HIGH TEMPERATURES.
FOCUS THEN TURNS TO VALLEY FOG AND FROST POTENTIAL TONIGHT INTO
EARLY THURSDAY MORNING. THE FOUR CORNERS TROUGH LIFTS NORTHEAST
ACROSS THE CENTRAL PLAINS TODAY AND INTO THE MID MISSISSIPPI RIVER
VALLEY LATE TONIGHT. MEANWHILE ANOTHER TROUGH WILL DIVE SOUTHEAST
OUT OF THE NORTHERN ROCKIES AND INTO THE DAKOTAS WEDNESDAY NIGHT
INTO EARLY THURSDAY MORNING. THE FORECAST AREA WILL BE IN BETWEEN
THESE TWO SYSTEMS WHICH RAISES THE QUESTION OF POTENTIAL CLOUD COVER
IMPACTING THE VALLEY FOG AND FROST POTENTIAL. THE NAM/GFS/ECMWF
SHOWS SOME CLOUDS SPILLING INTO THE AREA FROM THE NORTHWEST AND FROM
SOUTHWEST EARLY THURSDAY MORNING. HOWEVER...THE CLEAR SKIES OVER THE
REGION THIS EVENING INTO THE LATE NIGHT HOURS SHOULD LEAD TO GOOD
RADIATIONAL COOLING AND THE FORMATION OF SOME FROST AND POSSIBLY
VALLEY FOG. WILL HAVE TO KEEP A CLOSE EYE ON CLOUD TRENDS. PLAN ON
LOW TEMPERATURES TONIGHT RANGING FROM THE LOWER 30S OVER NORTH
CENTRAL WISCONSIN TO THE MID 30S ACROSS NORTHEAST IOWA.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 328 AM CDT WED OCT 16 2013
THE MID MISSISSIPPI RIVER VALLEY TROUGH WILL CONTINUE LIFTING
NORTHEAST ON THURSDAY AND IS EXPECTED TO STRETCH FROM SOUTHERN LAKE
MICHIGAN SOUTH INTO THE OHIO RIVER VALLEY. MEANWHILE THE TROUGH OVER
THE DAKOTAS WILL PUSH EAST INTO THE UPPER MISSISSIPPI RIVER VALLEY
BY LATE THURSDAY AFTERNOON. THE WAVE THEN EDGES EAST ACROSS THE
FORECAST AREA THURSDAY NIGHT BRINGING CHANCES FOR SHOWERS TO THE
AREA. A BROAD TROUGH THEN SETS UP ACROSS THE UPPER MISSISSIPPI RIVER
VALLEY AND WESTERN GREAT LAKES FRIDAY INTO FRIDAY NIGHT. WEAK
EMBEDDED SHORTWAVES WILL TRACK OVER THE REGION WITHIN THE TROUGH
FRIDAY INTO FRIDAY NIGHT BRINGING SLIGHT CHANCES FOR SHOWERS TO THE
AREA. A SECONDARY TROUGH THEN DIVES INTO THE REGION FROM CANADA
SATURDAY INTO SUNDAY...BRINGING THE COOLEST AIR OF THE SEASON THUS
FAR ALONG WITH CHANCES FOR RAIN SHOWERS. SOME SNOW MAY MIX IN
LATE...FRIDAY NIGHT...SATURDAY NIGHT...SUNDAY NIGHT AND POSSIBLY
AGAIN MONDAY NIGHT ACROSS NORTHERN WISCONSIN AND POSSIBLY AS FAR
SOUTH AS CENTRAL WISCONSIN. FORECAST MODELS ARE SHOWING SOME
DIFFERENCES IN 850 MB TEMPERATURES AND HOW FAR SOUTH THE COOLEST AIR
WILL BE. THE GFS SHOWS 850 MB TEMPERATURES FALLING TO AROUND -6 C
ACROSS THE ENTIRE FORECAST AREA BY EARLY SUNDAY MORNING. THE ECMWF
IS A LITTLE WARMER SHOWING 850 MB TEMPERATURES IN THE -3 TO -5 C
RANGE BY EARLY SUNDAY MORNING. THE TROUGH REMAINS OVER THE REGION
GOING INTO NEXT WEEK. ANOTHER TROUGH DIVES SOUTH OUT OF CANADA LATE
TUESDAY INTO WEDNESDAY AND THIS FEATURE HAS THE POTENTIAL TO BRING
SOME ACCUMULATING SNOW TO THE REGION. 850 MB TEMPERATURES COULD FALL
TO AROUND -10C BY THE MIDDLE OF NEXT WEEK. HIGH TEMPERATURES WILL BE
WELL BELOW NORMAL THIS WEEKEND INTO EARLY NEXT WEEK WITH HIGHS
MAINLY IN THE 40S WITH SOME LOCATIONS ACROSS NORTHEAST IOWA AND FAR
SOUTHWEST WISCONSIN POSSIBLY REACHING 50 DEGREES. PLAN ON OVERNIGHT
LOWS FALLING INTO THE 30S.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1228 PM CDT WED OCT 16 2013
TWO CONCERNS FOR THE AVIATION FORECAST...LINGERING STRATUS AND
POTENTIAL FOR FOG TONIGHT...ESPECIALLY AT LSE.
STRATUS PERSISTS ACROSS MUCH OF WI...SOUTHEAST MN AND NORTHEAST
IA...LINGERING IN THE WAKE OF A TROUGH OF LOW PRESSURE THAT MOVED
THROUGH THE TAF SITES LAST NIGHT. THE CLEARING LINE IS JUST
APPROACHING MSP AT 17Z...CO-LOCATED JUST EAST OF A SURFACE HIGH
PRESSURE RIDGE AXIS. AS THIS RIDGE PUSHES EAST...EXPECTING THE
CLEARING TO GO ALONG WITH IT. TIMING THIS CLEARING REMAINS
PROBLEMATIC...THOUGH...WITH MODEL GUIDANCE CONTINUING TO DELAY THE
CLEARING. THIS MAKES SENSE SO HAVE CLEARING GO THROUGH RST AT 23Z
AND LSE AT 03Z. THESE TIMES COULD EVEN BE PUSHED FURTHER BACK A
FEW HOURS IF THE SUN DOES NOT MIX OUT MORE OF THE NORTHWEST SIDE
OF THE CLOUDS. MVFR CEILINGS ARE ANTICIPATED TO PERSIST WHILE THE
STRATUS IS AROUND.
ONCE THE STRATUS CLEARS...WINDS WILL GO LIGHT AT LSE AS THE HIGH
PRESSURE RIDGE AXIS MOVES IN. THIS SETS POTENTIAL VALLEY FOG. HAVE
TRENDED THE FORECAST TOWARDS THIS POTENTIAL WITH A 4SM BR AND
SCT003 DECK. HOWEVER...CONCERNS OF CLOUDS MOVING UP FROM THE SOUTH
AS WELL AS TIMING THE CLEARING OF THE CURRENT STRATUS PRECLUDES
GOING LOWER ON CEILINGS AND VISIBILITIES. ADDITIONALLY...LOW LEVEL
WINDS ARE GOING TO INCREASE LATE IN THE NIGHT AHEAD OF A TROUGH
DROPPING THROUGH MN...WHICH COULD DISRUPT THE VALLEY FOG/STRATUS
PROCESS. THERE COULD ALSO BE SOME MVFR BR AT RST BUT THINK WINDS
WILL BE STRONG ENOUGH TO PREVENT IT. VFR CONDITIONS ARE EXPECTED
AT BOTH TAF SITES AFTER ANY FOG MIXES OUT IN THE MORNING.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...WETENKAMP
LONG TERM....WETENKAMP
AVIATION...AJ