Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 150825
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
325 AM CDT MON SEP 15 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 325 AM CDT MON SEP 15 2014

LATEST WATER VAPOR SATELLITE IMAGERY SHOWING VIGOROUS SHORTWAVE
TROUGH OVER THE DAKOTAS. 15.00Z UPPER AIR ANALYSIS INDICATES
STRONG JET CORE AT 300MB ACROSS EASTERN DAKOTAS INTO THE GREAT
LAKES REGION. LATEST MOSAIC RADAR SHOWS LIGHT RAIN EXPANDING
ACROSS SOUTHERN MINNESOTA...EASTERN SOUTH DAKOTA AND CENTRAL
WISCONSIN. THIS IS IN RESPONSE TO LIFT IN THE VICINITY OF THE
RIGHT ENTRANCE OF THE 300MB JET...STRONG PV ADVECTION AND DEEP QG
FORCING PER LATEST 15.00Z NAM/GFS/RAP.

MAIN FORECAST CONCERN TODAY IS MOVING THE PRECIPITATION OUT OF
THE FORECAST AREA TODAY...THEN FOG POSSIBILITIES IN RIVER VALLEYS
AND PATCHY FROST OVER CENTRAL WISCONSIN TONIGHT.

THE LATEST 15.00Z GFS/NAM ARE IN DECENT AGREEMENT IN TRACKING THE
SHORTWAVE TROUGH AND THE ASSOCIATED LIFT/FORCING/MOISTURE EAST OF
THE AREA BETWEEN 18-21Z TODAY. THIS IS IN GOOD AGREEMENT WITH THE
LATEST COMPOSITE REFLECTIVITY FROM THE MESO MODELS OF THE
HRRR/NAMNEST/ARW/NMM IN PUSHING PRECIPITATION EAST OF THE AREA
AROUND 19Z TODAY. HAVE ADJUSTED PRECIPITATION TRENDS AND SKY
CONDITION FOR THIS.

TONIGHT...THE LATEST 15.00Z GFS/NAM/ECMWF PROG SURFACE RIDGE OVER
THE WESTERN DAKOTAS TO BUILD INTO THE FORECAST AREA. LIGHT WINDS AND
CLEAR SKIES WILL ALLOW FOR A GOOD RADIATIONAL COOLING NIGHT. THE
15.00Z GFS/NAM BUFKIT SOUNDINGS SHOW WINDS LESS THAN 10 KNOTS BELOW
1500 FEET AFTER 06Z IN RIVER VALLEYS. THIS WILL ALLOW THE FORMATION
OF PATCHY FOG IN RIVER VALLEYS AND PARTS OF CENTRAL WISCONSIN.
ALSO...WITH LOW TEMPERATURES DROPPING INTO THE MIDDLE 30S ACROSS CENTRAL
WISCONSIN...PATCHY FROST WILL BE POSSIBLE.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 325 AM CDT MON SEP 15 2014

WITH THE SURFACE RIDGE DOMINATING THE FORECAST AREA TUESDAY AND INTO
WEDNESDAY MORNING. AREAS TO PATCHY FOG IS EXPECTED TO FORM
AFTER 06Z WEDNESDAY IN RIVER VALLEYS AND PARTS OF CENTRAL WISCONSIN.

THE LATEST 15.00Z GFS/NAM/ECMWF ARE CONSISTENT IN MOVING A WEAK
FRONT NORTH TO SOUTH ACROSS CENTRAL WISCONSIN WEDNESDAY
AFTERNOON/EVENING. THE MODELS SHOW WEAK 850MB THETA E CONVERGENCE IN
ASSOCIATION WITH THIS FRONT AND THE 15.00Z GFS/NAM GENERATE VERY
LIGHT QPF OVER CENTRAL WISCONSIN BY 00Z THURSDAY. POTENTIAL IS
THERE FOR MAYBE SPRINKLES OR VERY LIGHT RAIN SHOWERS.
HOWEVER...WITH THE BUFKIT SOUNDINGS SHOWING VERY SHALLOW MOISTURE
WILL CONTINUE TO LEAVE FORECAST DRY.

FOCUS THEN SHIFTS TO THURSDAY NIGHT INTO SATURDAY...AS THE 15.00Z
GFS/ECMWF/GEM INDICATE UPPER LEVEL RIDGE BREAKING DOWN AND DEVELOP
WEST TO EAST ZONAL FLOW ALOFT ACROSS THE NORTHERN TIER STATES. THE
BIGGEST DIFFERENCE BETWEEN THE MODELS WILL BE TIMING AND PLACEMENT
OF THE SHORTWAVE TROUGHS/SURFACE FEATURES ACROSS THE UPPER MIDWEST
AND GREAT LAKES REGION FRIDAY INTO FRIDAY NIGHT. THE LATEST 15.00Z
GFS/ECMWF/GEM ARE IN GOOD AGREEMENT IN INCREASING MOISTURE INTO THE
FORECAST AREA WITH DECENT MOISTURE TRANSPORT AT 925-850MB THAT
WILL PRODUCE HIGHER PRECIPITABLE WATER VALUES. THE LATEST 15.00Z
GFS ALSO SHOWS ENOUGH SHEAR AND SURFACE/ELEVATED INSTABILITY OVER
PORTION OF THE FORECAST AREA FRIDAY INTO FRIDAY NIGHT THAT COULD
LEAD A FEW OF THE THUNDERSTORMS TO POSSIBLY BE SEVERE. CONFIDENCE
IN THE EXACT PLACEMENT AND TIMING OF ANY OF THE THUNDERSTORMS AT
THIS TIME REMAINS LOW.

THE GREAT LAKES REGION REMAINS UNDER THE INFLUENCE OF THE UPPER
LEVEL TROUGH AND CYCLONIC FLOW SATURDAY INTO SUNDAY...PER THE 15.00Z
GFS/ECMWF. WILL CONTINUE TO LINGER SMALL PRECIPITATION CHANCES
ACROSS THE FORECAST AREA.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1120 PM CDT SUN SEP 14 2014

NARROW BAND OF SHOWERS CONTINUES ACROSS SOUTHERN MN/WESTERN WI...IN
A REGION OF ELEVATED FRONTOGENETIC FORCING. PCPN IS FALLING OUT OF
MID LEVEL CLOUDS WITH NO VSBY RESTRICTIONS. AS AN UPPER LEVEL
SHORTWAVE STARTS TO PUSH IN FROM THE NORTHERN PLAINS OVERNIGHT...THE
PCPN WILL BECOME MORE WIDESPREAD AND START TO SINK SOUTH. LOW LEVEL
RH INCREASES...PER BUFKIT SOUNDINGS...AND CONDITIONS LOOK FAVORABLE
FOR A DROP INTO MVFR CIGS FOR A FEW HOURS.

MESO MODELS TAKE THIS SYSTEM ACROSS THE REGION DURING THE
AFTERNOON...EXITING BY EARLY EVENING. PCPN SHOULD FOLLOW SUIT...BUT
A BIT EARLIER...MOVING EAST/SOUTHEAST OF THE TAF SITES BETWEEN 15-
18Z. SUBSIDENCE POST THE SHORTWAVE...ALONG WITH A SFC HIGH
INFLUENCING FROM THE CENTRAL PLAINS...SHOULD CLEAR SKIES LATER MON
AFTERNOON.

SEE A POTENTIAL FOR RIVER VALLEY FOG AT KLSE FOR TUE MORNING. WITH
EARLY MORNING PCPN...CLEARING SKIES...AND THEN A LIGHT WIND FIELD
MONDAY NIGHT...THE SETUP LOOKS GOOD. BIGGEST QUESTION MARK AT THIS
TIME WOULD APPEAR TO BE THE DEPTH OF THE LIGHT WIND LAYER. 00Z NAM
BUFKIT SOUNDINGS ARE SHALLOW FOR THE EVENING HOURS...BUT QUICKLY
DEEPENS OVERNIGHT. COULD BE ENOUGH FOR SUB 1SM VSBY FOG - PERHAPS
1/4SM.


&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION.....RIECK


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