712
FXUS63 KARX 071140
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
640 AM CDT THU JUL 7 2022
DISCUSSION
(TODAY THROUGH WEDNESDAY)
ISSUED AT 245 AM CDT THU JUL 7 2022
KEY MESSAGES:
- ISOLATED TO SCATTERED SHOWER/T-STORM CHANCES TODAY/TONIGHT
- RAIN CHANCES EXITING FRIDAY AFTERNOON THROUGH SATURDAY BUT RETURN
SUNDAY AFTERNOON THROUGH MONDAY
- SEASONABLE TEMPERATURES CONTINUE INTO NEXT WEEK
WATER VAPOR SATELLITE IMAGERY, LIGHTNING, AND 500MB HEIGHTS SHOW A
TROUGH APPROACHING THE PACIFIC NORTHWEST WITH A RIDGE OVER THE
ROCKIES EXTENDING TOWARD THE SOUTHERN PLAINS AND GULF STATES.
NORTHWEST FLOW ALOFT WAS OVER THE LOCAL AREA INTO THE GREAT LAKES
AND NEW ENGLAND STATES. SEVERAL AREAS OF CONVECTION WERE OCCURRING
EARLY THIS MORNING WITH ORGANIZED CLUSTERS OVER EASTERN COLORADO,
OVER THE NEB/KS STATE LINES INTO NORTHERN MISSOURI NEAR THE SURFACE
FRONT AND ALSO ACROSS MONTANA. THE MPX 00Z SOUNDING HAD A 1.18"
PRECIPITABLE WATER VALUE (PWAT) WITH A WEAK CAP IN PLACE TO 666MB.
PWATS ALONG THE FRONT ACROSS NORTHERN MISSOURI WERE IN THE 2" TO
2.25". THE FRONT ACROSS NORTHERN MONTANA HAD PWATS OF 1.4 INCHES.
TODAY THROUGH FRIDAY, WE'LL BE MONITORING THE PROGRESS OF THE
SHORTWAVE TROUGHS MOVING EAST FROM MONTANA AND FROM COLORADO ACROSS
THE PLAINS TODAY AND INTO IOWA/MINNESOTA. POCKETS OF UPPER LEVEL
JET SUPPORT ARE ASSOCIATED WITH THESE FEATURES, MID LEVEL
FRONTOGENESIS, AND VORTICITY ADVECTION WITH THE SHORTWAVES. AS IS
TYPICAL, THE HI RESOLUTION MODELS HAVE A VARIETY OF SOLUTIONS WITH
THE HIGHER CONFIDENCE CLOSER TO THE SURFACE FRONTS AS THESE
SHORTWAVE TROUGHS PUSH INTO THE AREA. THE NAM APPEARS TO SUFFER
FROM CONVECTIVE FEEDBACK WITH A MUCH STRONGER SOLUTION/STRONGER
MOISTURE TRANSPORT FARTHER NORTH ACROSS EASTERN IOWA INTO NORTHERN
ILLINOIS COMPARED TO THE OTHER DETERMINISTIC MODELS FOR TONIGHT AND
FRIDAY. WHILE THE GFS HAS A MORE MUTED SIGNAL AND THE EC HEAVY RAIN
APPROACHING THE SOUTHERN PART OF THE FORECAST AREA. SPC
MESOANALYSIS GRAPHICS AND 850MB ANALYSIS DATA SHOW A VERY MOIST
ATMOSPHERE IS IN PLACE OVER THE LOCAL AREA WITH 1.6 INCHES OF
PRECIPITABLE WATER. FORECAST SOUNDINGS FROM THE RAP SHOW LOW
LEVEL INSTABILITY IN PLACE THIS MORNING WITH A WEAK CAP AND
INSTABILITY ABOVE THE CAP...THEN THE CAP ERODING THIS AFTERNOON
WITH SBCAPE INCREASING TO AROUND 1200 J/KG AT KRST WITH THE CAP
WEAKENING A LITTLER EARLIER...AFTER 10AM. THE RAP/HRRR FORECAST
SOUNDINGS WERE ON THE WEAKER SIDE WITH 20KTS OF DEEP LAYER SHEAR.
CLOUD LAYER WINDS ARE 5 TO 15KTS, THUS SLOW MOVING. WITH THE
SHORTWAVE TROUGH TODAY THROUGH FRIDAY, THE AIRMASS SUPPORTS
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS. THE HRRR SEEMS TO
HANDLE THE CURRENT CONVECTION WELL WITH NOT MUCH LOCALLY THROUGH
THE DAY WITH A BAND OF SHOWERS/STORMS INCREASING AFTER 23Z NEAR
I90 AND PUSHING SOUTH AND ANOTHER BAND AROUND 10Z INTO EARLY
FRIDAY MORNING. THE 07.00Z HREF ALSO SUPPORTS SOME ISO/SCT
CONVECTION, BUT TOUGH TO CALL WHO WILL GET WET DUE TO THE HIT AND
MISS COVERAGE. ORGANIZED SEVERE WEATHER APPEARS LOW DUE TO THE LOW
SHEAR AND LOWER INSTABILITY, HOWEVER THE MOIST AIRMASS AND SLOW
STORM MOVEMENT SUPPORT HEAVY DOWNPOURS WHERE STORMS DO
FORM...INCREASING WITH HEATING TODAY AND THE HIGHER PROXIMITY TO
THE SHORTWAVE TONIGHT INTO EARLY FRIDAY. THE GEFS PLUMES HAVE
AROUND A QUARTER TO A THIRD OF AN INCH OF RAIN AT KLSE/KRST. THE
EC EPS IS SIMILAR WITH .2 OR .3" AT KLSE/KRST. OVER HALF THE
MEMBERS DO NOT HAVE 0.1" AND A COUPLE MEMBER HAVE 1 TO 2 INCHES.
THE CURRENT EXCESSIVE RAINFALL OUTLOOKS IN THE SLIGHT OR MODERATE
CATEGORY REMAIN TO THE SOUTH OF THE FORECAST AREA...SOUTH OF
WATERLOO AND DUBUQUE. THE FLOOD WATCHES REMAIN SOUTH OF OUR
FORECAST AREA CLOSER TO THE SURFACE FRONT.
CLOUD COVERAGE REMAINS ON THE HIGHER SIDE TODAY THROUGH FRIDAY
MORNING AND THIS SHOULD HELP KEEP TEMPERATURES IN THE 76 TO 85
DEGREE RANGE. IT WILL REMAIN MUGGY TODAY, BUT NOT QUITE AS MUGGY
LATER FRIDAY. STILL SEASONABLE FOR SATURDAY AS SURFACE HIGH
PRESSURE BUILDS INTO THE AREA, BUT NOT AS HUMID WITH DEWPOINTS IN
THE 50S.
A SHOWER OR STORM MAY MAKE IT INTO THE FORECAST AREA SUNDAY NORTH OF
I90, BUT A BETTER CHANCE WILL BE WITH THE LOWERING HEIGHTS AS A
SHORTWAVE TROUGH BREAKS DOWN THE RIDGE WITH A COLD FRONT MOVING INTO
THE REGION SUNDAY NIGHT AND MONDAY. WARMER HIGHS IN THE 80S AND A
RETURN TO 60S DEWPOINTS FOR SUNDAY AND MONDAY. RAIN CHANCES LOOK
SPOTTY TUESDAY AND WEDNESDAY WITH SEASONABLE HIGHS FROM THE MID 70S
TO MID 80S.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 638 AM CDT THU JUL 7 2022
FOG IMPACTING RST THIS MORNING WILL DISSIPATE IN THE NEXT HOUR OR
TWO. EXPECT MVFR VISIBILITIES AND IFR/LIFR CEILINGS UNTIL THEN. VFR
CONDITIONS ARE FORECAST FOR MOST OF TODAY WITH SHOWER AND STORM
CHANCES INCREASING THIS EVENING. STILL PLENTY OF UNCERTAINTY WITH
THIS SYSTEM, SO PRECIP TIMING AND THUNDER CHANCES MAY NEED TO BE
ADJUSTED IN FUTURE FORECASTS. LIGHT WINDS THROUGH THE TAF PERIOD
STARTING OUT SOUTHEASTERLY BEFORE SHIFTING TO EAST/NORTHEASTERLY
OVERNIGHT.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...ZAPOTOCNY
AVIATION...KAA
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