Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KARX 202034
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
334 PM CDT MON OCT 20 2014

.SHORT TERM...(THIS AFTERNOON THROUGH TUESDAY)
ISSUED AT 330 PM CDT MON OCT 20 2014

CHANGES TO THE FORECAST INCLUDE...INCREASED RAIN CHANCES WED
NIGHT INTO THURSDAY...INCREASED TEMPERATURES FRI-SUN.

THIS IS A NO/LOW WEATHER IMPACT FORECAST. WE ARE GETTING A BIT
BETTER CONSENSUS ON THE RAIN CHANCES FOR WEDNESDAY NIGHT AND
THURSDAY. ALSO INVESTIGATED WEEKEND WARM UP AND RIDGE
BUILDING...WITH GOOD SIGNAL NOW FOR A PERIOD OF ABOVE NORMAL
TEMPERATURES FROM FRI-SUN /10F+/.

OBSERVATIONAL DATA...
UPPER AIR DATA SHOWING UNIDIRECTIONAL N-NW FLOW THROUGH THE
TROPOSPHERE WITH UPSTREAM HIGHER LATITUDE RIDGE BUILDING RAPIDLY
EAST. 250 MB HEIGHT RISES OVER 40M/12HR OVER SRN MANITOBA THIS
MORNING..AND ALSO WIDESPREAD OVER THE WRN GREAT LAKES AT LOWER
LEVELS. LOW LEVEL CLOUDS ASSOCIATED WITH THE COLDER POOL OF AIR
SUB-INVERSION LEVEL...AND EAST OF THE STRONGEST FRONTAL REGION AT
850 MB /1-5C BAND/. LAPSE RATES ARE PRETTY STEEP SUB-INVERSION
LEVEL THERE...AND HAVE SEEN SOME SHRA IN NRN WI. CLOUDS PRETTY
CELLULAR SW OF I-94...AND SHOULD DISSIPATE QUICKLY WITH SUNSET.

TONIGHT THE RIDGE WILL CONTINUE TO BUILD EAST AND SUBSIDENCE
SHOULD REIGN WITH CLOUD MOVING EAST AND DISSIPATING. THERE IS
SOME WEAK SIGNAL IN THE SREF DATA FOR SOME CLOUD FRAGMENTS TO
SURGE WESTWARD AGAIN IN EASTERLY LOW-LEVEL FLOW TUESDAY MORNING.
HAVE NOT ADDRESSED THOSE YET IN THE FORECAST DUE TO LOW
CONFIDENCE...AND THEY SHOULD NOT MAKE FOR A BIG DEAL.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 330 PM CDT MON OCT 20 2014

CONTINUED THE FORECAST OF RIVER VALLEY FOG WEDNESDAY MORNING WITH
SIGNALS OF VERY DRY AIR ALOFT...LIGHT WINDS THROUGH ABOUT 15KFT
AND CLEAR SKIES. THE ONLY ITEM OUTSTANDING TO PREVENT AREAS OR
WIDESPREAD RIVER VALLEY FOG IS A SIGNAL FOR A BIT HIGHER WIND AT
INVERSION LEVEL ACROSS THE DETERMINISTIC MODELS. IF THE VALLEY
DECOUPLES...THIS LIKELY WILL NOT PREVENT THE FOG.

FEELING MORE CONFIDENT WITH WEDNESDAY NIGHT AND THURSDAY AS THE
DETERMINISTIC MODELS ARE AGREEING ON A SHORTWAVE TROUGH AT LEAST
EJECTING NORTHEAST INTO THE REGION...PRIOR TO WEAKENING. RETURN
SOUTHERLY FLOW...THE MOIST PLUME OF OVER 1 INCH PRECIPITABLE
WATER...AND EVEN 50-100 J/KG OF ELEVATED MU CAPE ALL SUGGEST A
NEARLY SATURATED ENVIRONMENT MOVING ACROSS THE FORECAST
AREA...THAT WILL GENERATE PRECIPITATION WITH ONLY WEAK FORCING.
THESE ELEMENTS ARE AGREED ON WITH THE 20.12Z DETERMINISTIC
NAM/GFS/EC/AND CANADIAN RUNS. THE ECMWF MODEL RUNS HAVE BEEN VERY
CONSISTENT FOR TWO DAYS NOW WITH THIS SYSTEM...AND THE OTHER
MODELS ARE CATCHING ON.

SO...HAVE INCREASED THE RAIN CHANCES MAINLY AFTER MIDNIGHT WED EVE IN
THE WEST...MOVING EAST THROUGH THE DAY THURSDAY. THE FORCING IS
QUITE WEAK WITH SOME WEAK WARM ADVECTION AND TROUGH CONVERGENCE...BUT
THINKING IS THAT THE ATMOSPHERE WONT NEED MUCH TO GENERATE SHRA/DZ.
RAIN CHANCES ARE NOW IN THE 50S FOR MUCH OF THE AREA...BUT THIS
MAY NEED TO BE HIGHER. MAINLY A LOW RAINFALL AMOUNT EVENT...MAYBE
1/4 INCH.

FRIDAY-MONDAY...

THE MAIN STORY SEEMS TO BE THE ABOVE NORMAL TEMPERATURES. WHILE
THE FRONTAL SURGES ARE NUMEROUS DURING THE PERIOD...FRIDAY AND
SUNDAY LOOK TO OFFER SOME WARM SECTORS ADVECTING INTO THE AREA.
CONSENSUS IN THE ENSEMBLES HAS INCREASED TOO WITH THE MEAN
TEMPERATURES IN THE LOWEST LEVELS INCREASING. TODAY AT KLSE IT
WAS 8C AT 925MB AND AT LEAST 65F...ON FRIDAY AND SUNDAY 925MB
WARMS TO A 20.12Z GFS/ECMWF MEAN OF 14C...SO IT SEEMS 70S ARE
WELL WITHIN REACH. THE 20.00Z NAEFS ANOMALIES STILL ARE IN THE 1-2
STANDARDIZED DEVIATION FOR THAT PERIOD IN THE 850MB
TEMPERATURES...BUT AM THINKING THIS WILL INCREASE WITH BETTER
AGREEMENT SEEN IN THE DETERMINISTIC RUNS THIS MORNING. THE SIGNAL
IS STARTING TO RESOLVE ITSELF. SO...INCREASED TEMPERATURES ABOVE
THE MODEL CONSENSUS THOSE DAYS...WITH MOS DEFINITELY TOO LOW.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1205 PM CDT MON OCT 20 2014

EXTENSIVE VFR CUMULUS FIELD ALONG AND EAST OF THE MISSISSIPPI
RIVER EARLY THIS AFTERNOON IN CYCLONIC FLOW ALOFT. EXPECT THIS
CUMULUS TO DISSIPATE WITH SKIES BECOMING SKC THIS EVENING AS A
RIDGE OF HIGH PRESSURE BUILDS IN FROM THE PLAINS. PLAN ON VFR/SKC
CONDITIONS THROUGH TUESDAY AS THE RIDGE CONTINUES TO BUILD
OVERHEAD.

&&

.CLIMATE...
ISSUED AT 330 PM CDT MON OCT 20 2014

RECORDS FOR THE WEEKEND ARE GENERALLY IN THE 75-80F RANGE AT LSE
AND RST. WHILE THE FORECAST IS STILL LOWER THAN THOSE VALUES...WE
WILL HAVE TO MONITOR THE MIXING DEPTH AND SKY COVER FOR FRIDAY AND
SUNDAY.
&&

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

$$

SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...BOYNE
CLIMATE...BAUMGARDT



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.