Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 242335
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
635 PM CDT THU JUL 24 2014

.SYNOPSIS...
ISSUED AT 316 PM CDT THU JUL 24 2014

LOW PRESSURE OVER WESTERN SD WILL MOVE EAST AND BE OVER SRN WI BY
SATURDAY EVENING. COLD FRONT WILL TRAIL THE LOW AND MOVE THROUGH
IOWA SATURDAY NIGHT. LOW PRESSURE WILL MOVE NORTHEAST ALONG THE
FRONT SATURDAY NIGHT. COOL HIGH PRESSURE WILL BUILD INTO THE
REGION SUNDAY THROUGH THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM /TONIGHT/...
ISSUED AT 316 PM CDT THU JUL 24 2014

LARGE AREA OF THETA-E ADVECTION AHEAD OF APPROACHING LOW PRESSURE
SYSTEM HAS ALLOWED FOR AREA OF THUNDERSTORMS ACROSS NORTHERN IOWA
AND WESTERN PORTIONS OF THE CWA. MODELS HAVE A POOR HANDLING ON THE
CURRENT SITUATION...INDICATING THAT PRECIPITATION WILL DECREASE.
WHILE SPC ANALYSIS SHOWS A RELATIVELY UNFAVORABLE ENVIRONMENT FOR
STORMS...GIVEN ONGOING PRECIPITATION AND STRENGTH OF THETA-E
ADVECTION...ANTICIPATE THIS TO CONTINUE THROUGH THE LATE AFTERNOON
AND EVENING HOURS. PRECIPITATION APPEARS TO BE ELEVATED...AND WILL
CONTINUE TO BE WITH VERY LIMITED SURFACE BASED CAPE. THEREFORE ANY
THREATS FOR SEVERE WEATHER WILL PRIMARILY BE LARGE HAIL.

AS LOW PRESSURE SYSTEM APPROACHES...PRECIPITATION WITH SHIFT TO THE
NORTH/NORTHEAST. IN ADDITION...LLJ IS EXPECTED TO
INCREASE...IMPINGING ON NORTH AND NORTHEASTERN PORTIONS OF CWA
BEGINNING NEAR 06Z. HAVE THEREFORE INCREASED POPS BEYOND 06Z. LLJ IS
EXPECTED TO PUSH SOUTH SOMEWHAT NEAR 12Z...AND HAVE BROUGHT HIGHER
POPS FURTHER SOUTH. MODELS ARE A BIT SLOWER...AND HAVE HUNG ON TO
PRECIPITATION THROUGH 12Z. PWAT VALUES OVERNIGHT REMAIN HIGH...OVER 1
INCH...AND LOCALLY HEAVY RAINFALL WILL BE POSSIBLE WITH
STORMS...HOWEVER DYNAMICS DECREASE OVERNIGHT...AND ANTICIPATE SEVERE
THREAT WILL ALSO DIMINISH.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 316 PM CDT THU JUL 24 2014

WARM FRONT WILL LIFT ACROSS THE CWA WITH STRONG CAPPING MOVING IN
RAPIDLY DURING THE DAY. H7 TEMPS WILL WARM TO +16 WITH CIN
REMAINING GREATER THAN -50 EVEN DURING MAX HEADING. DO NOT LOOK
FOR ANY PRECIP IN THE CWA AFTER EARLY FRIDAY MORNING THROUGH
FRIDAY NIGHT..AND ONLY LOW POPS ACROSS THE SOUTH WITH THE WAVE
PASSAGE SATURDAY AND SATURDAY NIGHT.

A STRONG PUSH OF WARM AIR ALOFT AND QUICK RETURN TO DEW POINTS IN
THE 70S AGAIN FOR FRIDAY. MUCH OF THE CWA WILL NOT HAVE A CHANCE
TO RECOVER ENOUGH TO REACH HEAT ADVISORY CRITERIA...BUT THE
SOUTHWEST IS LIKELY TO REACH 105 OR BETTER FOR A COUPLE HOURS
FRIDAY AFTERNOON. WILL HOIST A HEAT ADVISORY FOR THOSE AREAS FROM
17Z-00Z. CLOUDS AND COOLING WILL KEEP HEAT INDICES BELOW CRITERIA
FRO SATURDAY.

MUCH OF THE REST OF THE FORECAST PERIOD WILL BE DOMINATED BY COOL
CANADIAN HIGH PRESSURE. TEMPS WILL BE BELOW NORMAL THROUGH THE
WEEK. A DRY WEAK IS ON TAP UNTIL AT LEAST THURSDAY. ONCE THE HIGH
PRESSURE RETREATS TO THE EAST...RETURN FLOW WILL BRING A CHANCE
FOR THUNDERSTORMS WEDNESDAY NIGHT INTO THURSDAY.

&&

.AVIATION...25/00Z
ISSUED AT 635 PM CDT THU JUL 24 2014

PATCH OF SHRA CURRENTLY AFFECTING AREA MAY PRODUCE A BRIEF LOCAL
MVFR CIG/VSBY IN THE NEXT COUPLE OF HOURS BEFORE DISSIPATING...BUT
PROBABILITY AT A GIVEN TERMINAL IS LOW. THEREAFTER EXPECT A BREAK
IN PRECIP OF SEVERAL HRS WITH A RETURN TO SSE WINDS AND HIGH
CIGS...BUT OVERNIGHT AFTER 06Z ANTICIPATE MORE TSRA DEVELOPMENT
THOUGH COVERAGE IS QUESTIONABLE SO HAVE HANDLED WITH JUST VCTS FOR
NOW. BY 06Z ISSUANCE CONVECTIVE TRENDS MAY BE REVEALING THEMSELVES
ALLOWING FOR MORE DETAIL IN THE TAFS. BY MIDDAY FRIDAY EXPECT
STORMS WILL HAVE ENDED WITH VFR CONDITIONS PREVAILING DURING THE
AFTERNOON.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY FROM NOON TO 7 PM CDT FRIDAY FOR ADAMS-CASS-
RINGGOLD-TAYLOR-UNION.

&&

$$

SYNOPSIS...MS JUL 14
LONG TERM...MS JUL 14
AVIATION...LEE



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