Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 101146
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
646 AM CDT THU JUL 10 2014

.SHORT TERM /TODAY/...
ISSUED AT 325 AM CDT THU JUL 10 2014

SURFACE HIGH WILL CONTINUE TO DRIFT EASTWARD THROUGH THE DAY
TODAY WITH INCREASING SOUTHERLY FLOW AND WAA BEHIND HIGH. HAVE
WARMED TEMPERATURES UP FOR TODAY...GENERALLY NEAR OR ABOVE HIGHS
FROM WEDNESDAY WITH BETTER WAA. HIGH RES MODELS DEVELOP SCATTERED
PRECIP ACROSS THE NORTHEAST IN THE AFTERNOON WITH BAND OF WEAK
FORCING LIFTING INTO THE AREA. HOWEVER...GIVEN AMOUNT OF DRY AIR
HAVE OPTED TO KEEP FORECAST DRY FOR NOW. BIGGER CONCERN FOR POPS
WILL BE WITH APPROACHING SHORTWAVE ACROSS THE WEST. HAVE DELAYED
ONSET OF PRECIP SLIGHTLY INTO THE LATE AFTERNOON HOURS...WITH BEST
CHANCES IN THE NORTHWEST...THOUGH MAY STILL BE TOO QUICK WITH
ONSET AS BEST MOISTURE ARRIVES CLOSER TO 00Z.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 325 AM CDT THU JUL 10 2014

THE LONG TERM PORTION OF THE FORECAST PERIOD WILL ENTAIL A VARIETY
OF WX...RANGING FROM HEAVY RAINFALL AND SEVERE WEATHER POTENTIAL
EARLY IN THE FORECAST PERIOD TO THE POTENTIAL FOR RECORD LOW
TEMPERATURES LATE IN THE FORECAST PERIOD.

APPROACHING WESTERN CANADA H5 TROF WILL HELP PUSH THE EASTERN
CONUS H5 UPPER-LEVEL TROF EASTWARD EARLY IN THE PERIOD. A VIGOROUS
H5 SHORTWAVE WITH SFC COLD FRONT WILL SWEEP ESE THROUGH THE
FLOW...BRINGING CHANCES OF TSRA TO THE CWA BY LATE TONIGHT. BEST
CHANCES FOR SVR WX TONIGHT WILL REMAIN W OF THE CWA...WHERE THE
LLJ WILL BE FOCUSED ALONG WITH THE BEST THERMODYNAMIC AND
KINEMATIC FORCING. EXPECT THE MCS TO PUSH ESE ACROSS THE CWA EARLY
FRIDAY MORNING AND INTO THE DAY ON FRIDAY.

QUASI-STATIONARY FRONT IS EXPECTED TO EXTEND E-W ACROSS THE
SOUTHERN CWA ON FRIDAY. MODELS SUGGEST THE POTENTIAL FOR SEVERE WX
ESPECIALLY ACROSS THE WESTERN CWA...INVOF THE FRONT...ON FRIDAY.
BEST CHANCES WOULD BE ACROSS THE THE SOUTHWESTERN CWA WHERE BEST
COMBINATION OF INSTABILITY AND SHEAR VALUES ARE PROGGED TO EXIST.
INSTABILITY AND SHEAR PARAMETERS SUGGEST MOST LIKELY MODE OF
STORMS WOULD BE ISOLATED SUPERCELLS AND MULTICELLS...GROWING
UPSCALE INTO AN MCS AND MOVING EASTWARD OVERNIGHT INTO SATURDAY
MORNING.

GIVEN THE PRESENCE OF HEAVY RAINFALL PARAMETERS FROM LATE TONIGHT
THROUGH FRIDAY SUCH AS ELEVATED PWATS AS WELL AS PERSISENT
MOISTURE TRANSPORT AND THE QUASI-STATIONARY BOUNDARY...HAVE ADDED
HEAVY RAINFALL WORDING TO THE GRIDS WHERE POPS ARE LIKELY OR
GREATER. ATTM ANTICIPATE POTENTIAL ISOLATED FLOODING ISSUES BUT
NOT WIDESPREAD. WILL HAVE TO CONTINUE TO MONITOR HOWEVER FOR
POTENTIAL WATCH IF WARRANTED.

QUASI-STATIONARY BOUNDARY IS PROGGED TO REMAIN INVOF THE SOUTHERN
CWA ON SATURDAY. MAY SEE A REPEAT OF POTENTIAL SVR ADVERTISED ON
FRIDAY EXCEPT FARTHER SOUTH IN THE CWA. AGAIN...INSTABILITY AND
SHEAR PARAMETERS SUGGEST POTENTIAL FOR SUPERCELLS OR MULTICELLS ON
SATURDAY AFTERNOON.

SURFACE BOUNDARY IS PUSHED SOUTH OF THE CWA BY LATE SATURDAY INTO
SUNDAY WITH A REINFORCING SURFACE BOUNDARY OWING TO AN H5
SHORTWAVE ROTATING AROUND THE BASE OF THE ANOMALOUSLY DEEP H5 LOW
IN SOUTHERN CANADA. THIS LOW IS PROGGED TO IMPACT OUR WX THROUGH
THE END OF THE FORECAST PERIOD. GIVEN ANAMALOUSLY LOW THICKNESS
VALUES ACROSS THE CWA...WENT CONSIDERABLY LOWER FOR HIGH TEMPS ON
MONDAY AND TUESDAY...AS WELL AS FOR LOWS ON MONDAY NIGHT. PRESENT
THINKING IS THAT RECORD LOW TEMPERATURES FOR MONDAY NIGHT MAY BE
IN JEOPARDY...AS MAY BE THE RECORD LOW MAX TEMPS FOR MONDAY AND
TUESDAY.

&&

.AVIATION...10/12Z
ISSUED AT 637 AM CDT THU JUL 10 2014

EARLY MORNING MVFR BR AT SITES WILL LIFT SHORTLY AFTER 12Z. HIGH
PRESSURE WILL KEEP CONDITIONS VFR THROUGH 00Z...WITH WINDS FROM
THE SOUTH...POSSIBLY GUSTY. TSRA CHANCES WILL INCREASE FROM WEST
TO EAST BEYOND 00Z...ESPECIALLY BEYOND 06Z. HAVE ONLY INCLUDED
VCTS MENTION ATTM FOR SITES GIVEN UNCERTAINTIES IN TIMING AND
LOCATION OF TSRA.

&&

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

&&

$$

SHORT TERM...AWB
LONG TERM...ZOGG
AVIATION...AWB



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