Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Graphics & Text | 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 230449
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1149 PM CDT WED APR 22 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 243 PM CDT WED APR 22 2015

CURRENTLY AS OF 20Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED UPPER TROUGHS OVER BRITISH COLUMBIA...ALONG THE SOUTHERN
CALIFORNIA COAST...AND OVER THE FORECAST AREA INTO THE GREAT
LAKES...WHILE RIDGING EXTENDED FROM THE FOUR CORNERS OF THE U.S.
INTO ALBERTA. CYCLONIC FLOW OF MOISTURE AROUND THE GREAT LAKES UPPER
TROUGH...NICELY SEEN ON THE 12Z GRB SOUNDING...HELPING TO HOLD
STRATOCUMULUS ACROSS WI. GO A LITTLE MORE TO THE WEST OVER MN AND
IA...MUCH DRIER AIR WAS PRESENT ON THE 12Z MPX SOUNDING WITH A
PRECIPITABLE WATER OF 0.16 INCHES OR 36 PERCENT OF NORMAL. THIS
DRIER AIR HAS RESULTED IN CLEARER SKIES. A RIDGE OF HIGH PRESSURE
ACCOMPANYING THE CLEAR SKIES WAS LOCATED OVER THE EASTERN DAKOTAS. A
TIGHT PRESSURE GRADIENT EAST OF THIS RIDGE MAINTAINING A BRISK
NORTHWEST BREEZE OVER THE FORECAST AREA WITH SPEEDS/GUSTS A LITTLE
LOWER THAN 24 HRS AGO. STILL...THE SPEEDS HAVE BEEN STRONG ENOUGH TO
WARRANT THE EARLIER ISSUED WIND ADVISORY FOR A SMALL PORTION OF
NORTHEAST IOWA. AIRMASS REMAINS UNSEASONABLY COOL WITH 850MB TEMPS
IN THE -5 TO -8C RANGE...RESULTING IN THE PRESENT 40S
TEMPERATURES...AND EVEN 30S AT MEDFORD WI.

THE UPPER TROUGH AFFECTING THE FORECAST AREA INTO THE GREAT LAKES IS
PROGGED TO MAKE MUCH MORE EASTWARD PROGRESS OVER THE NEXT 24
HOURS...REACHING NEW ENGLAND BY 00Z FRI. THIS WILL ALLOW THE RIDGING
AND WARMER/DRIER AIR OVER THE NORTHERN ROCKIES AND PLAINS TO MARCH
TOWARDS THE FORECAST AREA. WE DO HAVE ONE SHORTWAVE TO CONTEND WITH
COMING DOWN THE BACK SIDE OF THE UPPER TROUGH TONIGHT...WHICH ITS
MAIN IMPACT IS TO BRING IN SLIGHTLY COOLER AIR FOR 12Z THU BEFORE
THE WARMING COMMENCES.

CLOUDS MAY BE A BIT PERSISTENT NORTHEAST OF I-94 TONIGHT...THANKS TO
THAT SHORTWAVE COMING THROUGH...BUT ELSEWHERE ANY STRATOCUMULUS WILL
DISSIPATE WITH LOSS OF DAYTIME HEATING. THIS CLEARING COMBINED WITH
WINDS DIMINISHING SOME AS THE RIDGE APPROACHES I-35 BY 12Z THU IS
EXPECTED TO RESULT IN A CHILLY NIGHT. 20S SHOULD BE COMMON ACROSS
MUCH OF THE REGION BY SUNRISE WITH PERHAPS NEAR 30 READINGS IN THE
MS RIVER VALLEY. NO FROST/FREEZE HEADLINES WILL BE POSTED YET AS
VEGETATION GROWTH IS NOT QUITE THERE. 850MB TEMPS ON THU CLIMB TO 0
TO -2C BY 00Z FRI WHICH WITH PLENTY OF SUN SHOULD BE ABLE TO BOOST
TEMPERATURES INTO THE LOW TO MID 50S FOR MOST LOCATIONS. MEDFORD
AGAIN MIGHT BE THE LONE COOLER EXCEPTION BEING CLOSER TO THE
DEPARTING COLD AIR. DEEP MIXING IS LIKELY AS WELL IN THE DRY AIRMASS
FEATURING PRECIPITABLE WATER NEAR 0.10 INCHES...CAUSING LOW RELATIVE
HUMIDITY VALUES. THE COMBINATION OF THESE LOW VALUES AND A 10 TO 15
MPH NORTHWEST BREEZE COULD RESULT IN SOME FIRE WEATHER CONCERN. SEE
FIRE WEATHER SECTION BELOW FOR MORE DETAILS.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 243 PM CDT WED APR 22 2015

FIRST FOCUS OF THE LONG TERM PERIOD IS ON THE UPPER TROUGH NEAR THE
SOUTHERN CALIFORNIA COAST. MODELS ARE IN GOOD AGREEMENT LIFTING THIS
TROUGH INTO THE CENTRAL PLAINS ON FRIDAY AND INTO CENTRAL ILLINOIS
ON SATURDAY. ALTHOUGH THIS TRACK IS SOUTH OF THE FORECAST AREA...WE
STILL HAVE SOME SHOT AT PRECIPITATION DURING THE FRIDAY-SATURDAY
TIME FRAME. PART OF THIS IS DUE TO A SOMEWHAT DECENT MOISTURE SURGE
AHEAD OF THE TROUGH UP INTO THE FORECAST AREA ON FRIDAY...REFLECTED
BY PRECIPITABLE WATER CLIMBING TO AROUND 0.75 INCHES BY 00Z SAT.
ADDITIONALLY...A SHORTWAVE IS PROGGED TO EJECT OUT OF THE TROUGH AND
MOVE THROUGH THE AREA ON FRIDAY...INTERACTING WITH THE MOISTURE.
THEREFORE...CHANCES OF PRECIPITATION PERSIST FOR FRIDAY...ESPECIALLY
IN THE AFTERNOON AND INTO THE NIGHT WEST OF THE MS RIVER WHERE MORE
MOISTURE EXISTS. PRECIPITATION SHOULD BEGIN TO WANE NORTH TO SOUTH
ON SATURDAY AS THE UPPER TROUGH MOVES EAST OF OUR LONGITUDE...
CUTTING OFF THE MOISTURE TRANSPORT AND ALLOWING DRIER AIR TO GET
DRAWN IN FROM THE NORTH AND EAST. SOME MODEL DIFFERENCES EXIST ON
HOW MUCH PRECIPITATION EXISTS ON SATURDAY DUE TO SLIGHT NORTH/SOUTH
DIFFERENCES OF THE UPPER TROUGH TRACK...WITH THE 22.12Z GFS/CANADIAN
FARTHEST NORTH UP TO US-10 AND 22.12Z NAM/ECMWF FARTHEST SOUTH TO
AROUND US-20. THEREFORE...PRECIPITATION CHANCES ON SATURDAY REMAIN
AT OR BELOW 50 PERCENT. BETWEEN THE CLOUDS AND PRECIPITATION...HIGH
TEMPERATURES LOOK TO BE A LITTLE COOLER THAN ON THU.

A DRIER AND WARMER PERIOD IS ON TAP FOR SUNDAY AS AN UPPER RIDGE
AXIS APPROACHES THE FORECAST AREA FROM THE WEST. WITH 850MB TEMPS OF
0-2C...SHOULD SEE HIGHS CLIMB WELL UP INTO THE 50S AND POSSIBLY 60S
IN RIVER VALLEYS. EASTERLY FLOW FROM HIGH PRESSURE OVER ONTARIO
LIKELY TO CAUSE RELATIVE HUMIDITIES TO TANK.

MODELS HAVE CHANGED THEIR TUNE A BIT FOR SUNDAY NIGHT THROUGH MONDAY
NIGHT...LEANING TOWARDS DRIER AND WARMER. THIS IS A RESULT OF A
SHORTWAVE TROUGH COMING INTO THE PACIFIC NORTHWEST ON SATURDAY
THAT...INSTEAD OF HEADING TOWARDS THE FORECAST AREA...NOW DIGS DOWN
INTO THE SOUTHERN PLAINS. THEREFORE HAVE FOLLOWED SUIT...DRYING OUT
THE FORECAST AND RAISING TEMPERATURES.

AS WE HEAD INTO TUESDAY AND WEDNESDAY...UPPER RIDGING IS PROGGED TO
DEVELOP OVER THE WESTERN U.S. INTO WESTERN CANADA...CAUSING
SHORTWAVES TO DROP INTO THE REGION ON NORTHERLY FLOW. AS A
RESULT...SOME LOW PRECIPITATION CHANCES ARE IN THE FORECAST. HARD TO
SAY HOW MUCH PRECIPITATION WILL FALL GIVEN LACK OF MOISTURE
AVAILABILITY. DESPITE THE NORTHERLY FLOW...850MB TEMPS ARE STILL
PROGGED IN THE 2-4C RANGE SO TEMPERATURES DO NOT LOOKS TO CHANGE
MUCH FROM MONDAY AND STAY JUST BELOW SEASONABLE NORMALS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1147 PM CDT WED APR 22 2015

SKIES WILL REMAIN MAINLY CLEAR THROUGH THE PERIOD. NORTHWEST WINDS
WILL REMAIN LESS THAN 10 KNOTS THROUGH 24.03Z...AND THEN BECOME
LIGHT SOUTHEAST.

&&

.FIRE WEATHER...
ISSUED AT 243 PM CDT WED APR 22 2015

TODAY HAS BEEN MOSTLY A DRYING DAY WEST OF THE MISSISSIPPI RIVER
WHERE MORE SUN HAS OCCURRED...CLOSER TO THE DRIER AIR OVER WESTERN
MN AND WINDS HAVE BEEN GUSTING 30-40 MPH. A WARMER DAY IS EXPECTED
ACROSS THE REGION ON THURSDAY WITH SUNNY SKIES. ADDITIONALLY...THE
DRY AIR OVER WESTERN MN MOVES IN...PLUMMETING RH VALUES TO 20-30
PERCENT. HOWEVER...WINDS DO NOT LOOK NEARLY AS STRONG WITH HIGH
PRESSURE MOVING IN...ONLY IN THE 10 TO 15 MPH RANGE. WITH SOME
GREEN-UP ALREADY OCCURRING AND THE LIGHTER WINDS...HAVE DECLINED
TO CONSIDER ANY FIRE WEATHER HAZARDS AT THIS TIME. SOME RAIN
REMAINS ON TAP TO MOVE INTO THE REGION FOR FRIDAY...ALONG WITH
CLOUDS...WHICH BOTH SHOULD HELP MITIGATE FIRE WEATHER CONCERNS.
LOOKING AHEAD...SUNDAY COULD BE ANOTHER DAY WORTH WATCH FOR FIRE
WEATHER CONCERNS...BUT SIMILAR TO THURSDAY WINDS ARE EXPECTED ON
THE LIGHTER SIDE.

&&

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

$$

SHORT TERM...AJ
LONG TERM...AJ
AVIATION...BOYNE
FIRE WEATHER...AJ


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