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000
FXUS63 KARX 191107
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
607 AM CDT WED JUN 19 2013

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 350 AM CDT WED JUN 19 2013

MAIN FORECAST CONCERNS THIS PERIOD...SHRA/TSRA CHANCES LATER
TONIGHT/THU...TEMPERATURES.

DATA ANALYSIS AT 06Z HAD A BROAD AREA OF HIGH PRESSURE CENTERED
FROM WESTERN QUEBEC INTO EASTERN WI...WHILE LOW PRESSURE WAS TAKING
SHAPE IN THE LEE OF THE CO TO MT ROCKIES. HIGH PRESSURE WAS
BRINGING GENERALLY CLEAR SKIES AND SEASONABLY COOL TEMPS TO MOST OF
THE UPPER MIDWEST EARLY THIS MORNING...ESPECIALLY WI AND NORTHEAST
MN WHERE THE AIRMASS WAS DRIER CLOSER TO THE CENTER OF THE HIGH.
EARLY MORNING TEMPS IN THESE AREAS WERE MOSTLY IN THE 40S-LOWER 50S.

19.00Z MODELS LOOK TO HAVE INITIALIZED WELL AND OFFER QUITE SIMILAR
SOLUTIONS FOR TODAY THRU THU AS THE PATTERN SLOWLY PROGRESSES AND
MOISTURE/INSTABILITY/TEMPS INCREASE ACROSS THE REGION. DPROG/DT OF
500MB HGTS AT 19.00Z SHOWED THE MODEL RUNS OF 17.00Z AND 18.00Z
VERIFIED QUITE WELL ACROSS NOAM/EASTERN PAC EVEN ON SMALLER SCALE
FEATURES IN THE FLOW. MODELS GENERALLY CONVERGING ON A TIGHTER
CONSENSUS TODAY THRU THU AS SHORTWAVE ENERGY EAST OF WYOMING EARLY
THIS MORNING MOVES EAST THRU THE RIDGE AXIS AND THE WEST COAST MID
LEVEL LOW MOVES INTO THE NORTHERN ROCKIES. TREND LEANS A BIT SLOWER
WITH THE SHORTWAVE ENERGY MOVING THRU THE RIDGE TOWARD/ACROSS THE
AREA TONIGHT/THU. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED ALL
LOOKING GOOD WITH THE SFC MASS FIELDS OVER THE CENTRAL CONUS. PER
WV IMAGERY...A COMPROMISE OF THE AVAILABLE MODELS LOOKED BEST WITH
THE SHORTWAVE ENERGY FROM NEAR THE BLACK HILLS TO WESTERN KS. GIVEN
THE TREND TOWARD A TIGHTER CONSENSUS AND NO ONE MODEL LOOKING LIKE
A FAVORITE...USED THE MODEL/ENSEMBLE CONSENSUS. SHORT TERM FCST
CONFIDENCE ON THE GOOD SIDE THIS CYCLE.

QUIET WEATHER ACROSS THE AREA TODAY AS THE HIGH REMAINS IN CONTROL
AND THE MAIN MOISTURE/INSTABILITY AXIS AND LOWER LEVEL THERMAL RIDGE
REMAIN WEST OF THE FCST AREA. WITH A SFC-700MB RIDGE AXIS REMAINING
OVER/WEST OF THE FCST AREA LEFT TODAY DRY...EVEN AS SOME MOISTURE
INCREASE AND CAPE DO START TO SPREAD INTO THE WEST END OF THE FCST
AREA THIS AFTERNOON. 925 MB TEMPS WARM SOME 2 TO 3C OVER THOSE OF
TUE...WITH HIGHS TODAY UNDER PLENTIFUL SUNSHINE LOOKING TO TOP OUT
IN THE UPPER 70S TO LOWER 80S ACROSS MOST OF THE FCST AREA.

MAIN INSTABILITY AXIS REMAINS WEST OF THE FCST AREA TONIGHT HOWEVER
PW VALUES CONTINUE TO INCREASE AND THE WEAK MID LEVEL SHORTWAVE
APPROACHES. SOME WEAK PV ADVECTION ALOFT INDICATED...ALONG WITH 850-
700MB THETA-E CONVERGENCE AND PW VALUES INCREASING INTO THE 1 TO
1.5 INCH RANGE. CONTINUED THE TREND OF A 20-30 PERCENT SHRA/TSRA
CHANCE SPREAD INTO THE NORTHWEST HALF OF THE FCST AREA MAINLY AFTER
MIDNIGHT.

PW VALUES INCREASE INTO THE 1.5 TO 1.75 INCH RANGE THU AS LOWER
LEVEL WARM/MOISTURE ADVECTION CONTINUE OVER THE UPPER MIDWEST. ML
CAPE INCREASES INTO THE 1K-2K J/KG RANGE WITH LITTLE IN THE WAY OF
CAPPING. HOWEVER 0-6KM SHEAR ON THE WEAK SIDE THUS ANY SEVERE THREAT
THU AFTERNOON LOOKS TO BE SMALL. THE WEAK MID LEVEL SHORTWAVE PASSES
THU AND CARRIED 30-50 PERCENT SHRA/TSRA CHANCES...HIGHEST OVER THE
CENTRAL/NORTHWEST PORTIONS OF THE FCST AREA WHERE LOW LEVEL MOISTURE
TRANSPORT/THETA-E CONVERGENCE ARE BETTER FOCUSED.

TRENDED TOWARD WARMER OF GUIDANCE HIGHS TODAY THEN USED A BLEND OF
THE GUIDANCE FOR LOWS/HIGHS TONIGHT/THU.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 350 AM CDT WED JUN 19 2013

MODELS CONTINUE THE TREND OF AN IMPROVING CONSENSUS IN THE THU NIGHT
THRU FRI NIGHT PERIOD AS SOUTHWEST FLOW ALOFT BECOMES ENTRENCHED
OVER THE AREA AND PIECES OF SHORTWAVE ENERGY EJECT OUT OF THE
WESTERN NOAM TROUGH INTO THE UPPER MIDWEST. THIS PERIOD LOOKING
QUITE UNSETTLED WITH A COUPLE PERIODS OF STRONGER/MORE WIDESPREAD
SHRA/TSRA POSSIBLE. FORECAST CONFIDENCE IN THIS TIME FRAME MEDIUM.

ONE OF THE MORE INTERESTING PERIODS IS LOOKING TO BE THU NIGHT FRI
MORNING. LOWER LEVEL THERMODYNAMIC FORCING/MOISTURE TRANSPORT/THETA-
E CONVERGENCE ON NOSE OF THE 850MB JET POINT TO CONVECTIVE COMPLEX
DEVELOPMENT IN/NEAR WEST-CENTRAL MN THU EVENING. CORFIDI VECTORS
WOULD TRACK THIS COMPLEX EAST/SOUTHEAST OVERNIGHT AROUND THE EDGE OF
THE MID LEVEL CAPPING...INTO THE FCST AREA LATER THU NIGHT/FRI
MORNING. SWODY2 FOR A THREAT OF DAMAGING WINDS LATER THU NIGHT
QUITE REASONABLE AS WHAT WOULD BE A MATURE MCS MOVES INTO THE AREA.
THIS WOULD ALSO HAVE THE POTENTIAL OF PRODUCING 1 TO 2 INCHES OF
RAIN AS PW VALUES IN THE INFLOW AIRMASS ARE IN THAT RANGE. CARRIED
40-60 PERCENT SHRA/TSRA CHANCES BY LATER THU NIGHT.

MODELS BEGIN TO DIFFER ON THE DETAILS FOR FRI/FRI NIGHT...BUT
SOME FORM LOWER LEVEL THERMO-DYNAMIC FORCING CONTINUE OVER MOST OF
THE UPPER MIDWEST. QUESTIONS ARE THE STRENGTH OF THE MID LEVEL
CAPPING...WHERE THE STRONGER FORCING MAY BE /AS A RESULT OF
BOUNDARIES FROM EARLIER CONVECTION/ AND SHORTWAVES TRAVELING THRU
THE SOUTHWEST MID LEVEL FLOW. 40-50 PERCENT SHRA/TSRA CHANCES FOR
FRI/FRI NIGHT LOOK GOOD AT THIS TIME. CONVECTIVE SCENARIO PER SWODY3
FOR ANOTHER CONVECTIVE COMPLEX TO ROLL INTO/ACROSS THE AREA LATER FRI
NIGHT WELL WITHIN THE REALM OF POSSIBILITIES.

LOWER LEVEL AIRMASS CONTINUES TO WARM THRU FRI NIGHT. 925-850MB
TEMPS BY FRI WOULD SUPPORT HIGHS OF 85-90...BUT THIS WOULD BE
DEPENDENT ON MORE SUNSHINE THAN CLOUDS/SHRA/TSRA. USED THE
MODEL/ENSEMBLE CONSENSUS FOR LOWS/HIGHS THU NIGHT THRU FRI NIGHT.

MEDIUM RANGE MODEL RUNS OF 19.00Z CONTINUE THE UNSETTLED PATTERN
THRU THE WEEKEND INTO EARLY NEXT WEEK...HOWEVER PLENTY OF DETAIL
DIFFERENCES BY DAYS 4-7. FCST CONFIDENCE ON ANY ONE DAY BELOW
AVERAGE DUE TO THE IMPACTS OF THE DETAIL DIFFERENCES ON THE
RESULTING SENSIBLE WEATHER. THRU THE WEEKEND...A REASONABLE
CONSENSUS FOR THE NORTHERN ROCKIES TROUGH TO LIFT NORTHEAST INTO
CENTRAL CAN. BROAD SCALE DIVERGENCE ALOFT CONTINUES OVER THE AREA
WITH MORE WEAKER SHORTWAVES TO RIPPLE THRU THE FLOW AND THE VERY
MOIST/UNSTABLE AIRMASS TO REMAIN OVER THE REGION. DEPENDING ON
TIMINGS AND LOCATIONS OF LOWER LEVEL/SFC FORCING MECHANISMS...ONE
OR MORE OF THE SAT-TUE PERIOD LIKELY TO END UP DRY...BUT
DETERMINING WHICH ONES IS NEARLY IMPOSSIBLE AT THIS TIME.
CONTINUED TO FOLLOW THE MODEL/ENSEMBLE CONSENSUS FOR SHRA/TSRA
CHANCES FOR SAT-TUE...WHICH MAKES THE FCST SOUND LIKE A BROKEN
RECORD. CONVECTIVE OUTCOMES ON ANY ONE DAY WILL HAVE BIG IMPACTS
ON HIGH TEMPERATURES. 925-850MB TEMPS WOULD SUPPORT HIGHS OF 90-95
AT LEAST SAT-MON...IF THE DAYS WOULD END UP ON THE DRIER SIDE WITH
PARTLY CLOUDY/MOSTLY SUNNY SKIES. GIVEN THE LOWER DAY-TO-DAY
CONFIDENCE IN THIS PERIOD...STAYED CLOSE TO THE MODEL/ENSEMBLE
CONSENSUS HIGHS/LOWS FOR DAYS 4-7 AS WELL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 606 AM CDT WED JUN 19 2013

A SOUTHEASTERLY FLOW OF DRY AIR OUT OF HIGH PRESSURE IN EASTERN
WISCONSIN WILL HELP KEEP CONDITIONS VFR THROUGH TONIGHT. THERE ARE
INDICATIONS OF AN UPPER LEVEL LOW PRESSURE TROUGH APPROACHING RST
TOWARDS 12Z. AHEAD OF THIS TROUGH...HIGH BASED STRATUS IS LIKELY
TO DEVELOP AND POSSIBLY EVEN SOME SHOWER/THUNDERSTORM ACITIVTY.
CONFIDENCE ON THE PRECIPITATION IS TOO LOW TO INCLUDE IN THE RST
TAF. PLAN ON WINDS GENERALLY 10 KT OR LESS FOR SPEEDS...BUT COULD
GET GUSTY THIS AFTERNOON...ESPECIALLY AT RST.

&&

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

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION...AJ