Area Forecast Discussion
Issued by NWS Des Moines, IA

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 KDMX 041144
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
644 AM CDT TUE AUG 4 2015

.SHORT TERM /TODAY/...
ISSUED AT 411 AM CDT TUE AUG 4 2015

CURRENTLY HAVE AN AREA OF SFC HIGH PRESSURE SITUATED ACROSS MUCH OF
THE STATE...WITH AN AREA OF LOW PRESSURE DEVELOPING ALONG THE FRONT
RANGE OF THE ROCKIES. HAVE A FRONTAL BOUNDARY ALOFT STRETCHING FROM
CENTRAL AND WESTERN SD SOUTHEASTWARD THROUGH ERN NE...SW IA AND INTO
NRN MO. SOUTHERLY H85 FLOW AND WAA IN PLACE WITH THETA-E ADVECTION
AS WELL. THIS HAS ALLOWED FOR A LINE OF THUNDERSTORMS TO DEVELOP
ALONG THE BOUNDARY ALOFT. THIS FRONT IS EXPECTED TO LIFT SLOWLY
NORTH/NORTHEASTWARD TODAY WITH CONTINUED CHANCES FOR SHOWERS AND
THUNDERSTORMS IN ITS VICINITY. AS FOR TEMPERATURES HAVE KEPT MAX
TEMPS SIMILAR TODAY TO READINGS FROM MONDAY WITH A SIMILAR AIRMASS
IN PLACE ACROSS MUCH OF THE CWA. AREAS SEEING THE WAA WILL ALSO HAVE
MORE CLOUD COVER AND THE PRECIP CHANCES SO OVERALL MAYBE ONLY WARMED
THEM A DEGREE OR TWO AT MOST.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 411 AM CDT TUE AUG 4 2015

BY AROUND 12Z WED...A SHORTWAVE LOOKS TO RIDE NEAR TO THE IA/MO
BORDER AND CLIP SOUTHERN IOWA. A BOUNDARY ATTACHED TO LOW PRESSURE
NORTH OF MONTANA LOOKS TO PROVIDE ADDITIONAL SUPPORT FOR PRECIP IN
THE FORM OF WEAK LOW LEVEL MOISTURE CONVERGENCE. PWATS APPEAR TO BE
IN THE 1.5 INCH TO 1.75 INCH RANGE AS THIS SYSTEM PROPAGATES
EASTWARD. NOT A LOT OF SUPPORT ALOFT AS NO MID TO UPPER LEVEL JETS
PRESENT. MINIMAL CAPE VALUES PLUS SHEAR OF LESS THAN 20 KTS...
POINTS TOWARDS NO CONVECTIVE/SVR THREAT. 850MB TEMPS FOR WED VERY
SIMILAR TO TUE 850MB TEMPS. FCST SOUNDINGS SUGGEST LOWER CLOUD BASES
AND MORE CLOUD COVER WED...ESPECIALLY SOUTH OF I-80. THEREFORE...
STARTED WITH PERSISTENCE AND THEN LOWERED WED MAX TEMPS A FEW
DEGREES.

ACTIVE WEATHER THEN SETS UP FOR THURSDAY INTO FRIDAY. MODELS IN
EXCELLENT AGREEMENT WITH PASSING A SFC LOW EASTWARD FROM SOUTH
DAKOTA THURSDAY MORNING INTO WESTERN WISCONSIN BY FRIDAY MORNING.
MODELS ALSO BRING AN ATTENDANT COLD FRONT WITH THIS LOW THROUGH
NORTHERN IOWA. TIMING WILL BE KEY WITH THIS BOUNDARY PASSAGE. AS OF
NOW...IT APPEARS THE BOUNDARY WILL NOT ENTER THE DMX CWA UNTIL BTX
00Z FRI AND 06Z FRI. SVR THREAT WITH THIS BOUNDARY PASSAGE CERTAINLY
APPEARS LEGIT. 0 TO 6 KM BULK SHEAR VALUES IN THE 40 TO 45 KT RANGE
WITH THIS SYSTEM. 0 TO 6 KM MUCAPE VALUES HIT THE 2000 J/KG MARK.
FOR SVR WX MODE...DCAPE VALUES NEAR 1400 J/KG. TIMING OF BOUNDARY
PASSAGE HIGHLY CLIMATOLOGICAL FAVORS WIND EVENT. LARGE HAIL ALSO
POSSIBLE...ESPECIALLY EARLY ON AND TO THE FAR NW.

HIGH PRESSURE WILL BE MOVING IN BEHIND THIS FRONT...MAKING IT INTO
WESTERN IOWA BY 00Z SAT. THIS HIGH SHOULD KEEP FRIDAY PM DRY AND MAY
BRING THE SUN BACK OUT. CAA COMES IN ADVANCE OF THIS HIGH AS 850MB
TEMPS SHOULD BE AROUND 16C TO 18C AT 12Z FRI. IT LOOKS LIKE THIS
HIGH SHOULD PASS QUICKLY WITH WARMER AIR FOLLOWING THIS HIGH TO OUR
WEST. AS OF NOW...IT APPEARS THE DMX CWA SHOULD HAVE A STRONG
NORTHERLY COMPONENT TO THE FLOW DURING DAYLIGHT HOURS FRIDAY. IF
FUTURE MODEL RUNS SPEED UP THIS HIGH AND GET RETURN FLOW TO OUR
WESTERN EDGE BY AFTERNOON...MAX TEMPS WILL CERTAINLY NEED TO BE
BUMPED UP...LIKELY BY 5 DEGREES AT LEAST.

FOR THE WEEKEND...STRONG UPPER LEVEL HIGH PRESSURE RE-ESTABLISHES
ITSELF NEAR THE OK/TX PANHANDLE. WITH AN UPPER LEVEL LOW EXPECTED TO
SKIT ALONG THE CANADA/US BORDER...IOWA SHOULD ONCE AGAIN RETURN TO
WESTERLY/NW FLOW ALOFT. MODELS TRY TO BRING SEVERAL SHORTWAVES INTO
IOWA SATURDAY THROUGH THE END OF THE FCST PERIOD. SO HAVE LEFT BROAD-
BRUSHED POPS IN THE EXTENDED. 850 MB TEMPS SHOULD BE AROUND 16C TO
20C DURING THIS TIME PERIOD. WITH CLOUDS AND PRECIP VERY
POSSIBLE...THIS SUGGESTS TEMPERATURES SLIGHTLY BELOW NORMAL IN THE
LOW TO MID 80S.

&&

.AVIATION...04/12Z
ISSUED AT 644 AM CDT TUE AUG 4 2015

VFR CONDITIONS EXPECTED FOR THE CRITICAL TAF PERIOD. HIGH CLOUDS
EXPECTED ACROSS THE AREA WITH A CIRRUS SHIELD IN PLACE FROM STORMS
ACROSS NE/SW IA. FRONTAL BOUNDARY LIFTING NORTH/NORTHEASTWARD
TODAY...WILL ALLOW FOR RAIN CHANCES TO PUSH INTO THE WESTERN TAF
SITES TONIGHT AND ALL TAF SITES JUST BEYOND THE CURRENT FORECAST
PERIOD. HAVE INCREASING LOWER CLOUDS THROUGH THE PERIOD...MAINLY
IN THE LOW VFR RANGE. WINDS TO BE LIGHT AND VARIABLE BECOMING MORE
SOUTHEASTERLY THROUGH THE PERIOD.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...BEERENDS
LONG TERM...KOTENBERG
AVIATION...BEERENDS


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