NWS-La Crosse Forecast Discussion

						FXUS63 KARX 082005
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
305 PM CDT TUE JUL 8 2008

.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT

FORECAST CONCERNS ARE ON TEMPERATURES THROUGH WEDNESDAY THEN RAIN
CHANCES ON THURSDAY AND THURSDAY NIGHT WITH MCS.

18Z SURFACE ANALYSIS SHOWS COLD FRONT EXTENDING FROM MAUSTON TO
OELWEIN AND PROGRESSING STEADILY SOUTHWARD. DEWPOINTS AROUND 70 TO
THE SOUTH OF THE FRONT WITH SBCAPE 1000 J/KG-2000 J/KG. EFFECTIVE
SHEARS OFF THE SPC MESO PAGE ONLY AROUND 20 KNOTS. A NARROW LINE OF
CONVECTION HAS DEVELOPED ALONG THE FRONT. THUS DO NOT EXPECT THESE
TO REACH SEVERE LEVELS BUT WILL PRODUCE SOME LOCALLY HEAVY DOWNPOURS
OF RAIN.

08.12Z DETERMINISTIC MODELS IN GOOD AGREEMENT THROUGH THE PERIOD.
TYPICAL SUMMER PATTERN TO CONTINUE WITH MAIN BAND OF WESTERLIES
ACROSS THE NORTHERN TIER OF STATES. IN THE NEAR TERM...FRONT WILL
PUSH SOUTH OF THE AREA BY 00Z TONIGHT. MUCH DRIER AIR THEN ADVECTS
IN BEHIND IT WITH SURFACE DEWPOINTS ALREADY IN THE UPPER 40S TO
LOWER 50S ACROSS MINNESOTA. THESE SETTLE ACROSS THE AREA AS HIGH
PRESSURE BUILDS SOUTHWARD. LIGHT WINDS AND CLEAR SKIES EXPECTED
THROUGH THE OVERNIGHT HOURS.

BUFKIT SOUNDINGS INDICATE SOME CUMULUS DEVELOPING WEDNESDAY
AFTERNOON OTHERWISE MOSTLY SUNNY SKIES EXPECTED WITH THE HIGH
OVERHEAD. BY WEDNESDAY NIGHT...HIGH BEGINS TO SLIDE EAST OF THE AREA
AND RETURN FLOW PUSHES MOISTURE NORTHWARD ACROSS THE PLAINS. SOME
MODEL DIFFERENCES WITH LOW LEVEL JET AS NAM/WRF SHOWS 40 KNOTS...
WHILE GFS WEAKER WITH ONLY 25 TO 30 KNOTS. NONE THE LESS LOOKS LIKE
CONVECTIVE DEVELOPMENT LATE ACROSS THE NORTHERN PLAINS...WITH
CORFIDI VECTORS POINTING TO AN EAST/SOUTHEAST MOVEMENT. WILL KEEP
AREA DRY WEDNESDAY NIGHT AND THEN RAISE POPS SLIGHTLY INTO THE HIGH
CHANCE CATEGORY FOR THURSDAY AS MCS TRANSLATES ACROSS THE AREA.
ENOUGH TIME TO FIGURE OUT THE DETAILS WITH FUTURE MODEL RUNS.

WITH MOISTURE TRANSPORT CONTINUING INTO THE AREA THURSDAY NIGHT WILL
KEEP LOW POPS GOING ACROSS THE NORTHERN SECTIONS OF THE FORECAST
AREA.

NEXT SHORTWAVE THEN POISED TO TRAVERSE ALONG THE CANADIAN BORDER
FRIDAY PUSHING A COLD FRONT TOWARD THE AREA. RAIN CHANCES LOOK TO
INCREASE THROUGHOUT THE DAY AND FRIDAY NIGHT. WILL CONTINUE CHANCE
POPS ACROSS THE AREA DURING THIS TIME FRAME.

AS FOR TEMPERATURES...EXPECT A BRIEF COOL DOWN BEHIND THE FRONT
WITH LOWER HUMIDITY LEVELS TONIGHT THROUGH WEDNESDAY. THEN AS
SOUTHERLY FLOW RE-ESTABLISHES ITSELF LATE WEDNESDAY EXPECT
TEMPERATURES AND HUMIDITY LEVELS TO ONCE AGAIN CLIMB PERHAPS
HITTING 90 BY FRIDAY AFTERNOON AHEAD OF THE COLD FRONT.

.LONG TERM...SATURDAY THROUGH TUESDAY

06Z GFS AND 00Z ECMWF DETERMINISTIC MODELS HAVE SIMILAR SOLUTIONS
THROUGH THE PERIOD. RATHER VIGOROUS SHORTWAVE MOVING ACROSS
SOUTHERN CANADA AT THE BEGINNING OF THE PERIOD WILL DRAG A COLD
FRONT THROUGH THE FORECAST AREA. BOTH DETERMINISTIC MODELS POINT TO
THIS FRONT EXITING THE AREA LATER SATURDAY AFTERNOON. WILL CONTINUE
POPS ON SATURDAY WITH SATURDAY NIGHT THROUGH MONDAY DRY AS HIGH
PRESSURE MOVES ACROSS THE UPPER MIDWEST. SOME DIFFERENCES IN TIMING
OF RETURN FLOW EARLY NEXT WEEK ON BACK SIDE OF THE HIGH. WILL TAKE
A BLEND APPROACH PER HPC GUIDANCE...KEEPING MONDAY DRY WITH POPS
AHEAD OF THE NEXT FRONT ON TUESDAY. TEMPERATURES LOOK TO TO BE AROUND
THE SEASONAL NORMALS BEHIND THE FRONT WITH THE WARMEST DAY LOOKING
TO BE SATURDAY.

&&

.AVIATION...

PASSAGE OF COLD FRONT TODAY BRINGS MUCH DRIER AIR TO THE AREA FOR
THIS FORECAST PERIOD WITH VFR CONDITIONS EXPECTED THROUGHOUT.
MOISTURE WILL BE LACKING THROUGH THIS TIME PERIOD...AND WITH THE
DEPARTURE OF THE COLD FRONT...AND SUBSIDENT AIR OVERHEAD...SKIES
WILL BE CLEAR OVERNIGHT. MODELS DO BRING SMALL AMOUNTS OF MID-LEVEL
MOISTURE ACROSS THE TAF SITES AS A 500MB SHORTWAVE ENERGY PASSES BY
LATE TONIGHT. ALTHOUGH THE FORMATION OF THESE CLOUDS IS IN QUESTION
DUE TO THE LACK OF MOISTURE...DID LEAVE IN A SCATTERED DECK OF
MID-CLOUD DURING THIS TIME.

&&

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

$$

SHORT AND LONG TERM - RABERDING
AVIATION - BROOKS