Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 232018
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
318 PM CDT SAT APR 23 2016

.SHORT TERM.../TONIGHT/
ISSUED AT 312 PM CDT SAT APR 23 2016

DEEP UPPER LEVEL TROUGH SPINNING OVER THE CENTRAL ROCKIES...WITH
AN ASSOCIATED SURFACE LOW DEVELOPING IN LEE OF THE ROCKIES.
SOUTHERLY FLOW TO INCREASE ACROSS THE REGION WITH WAA AHEAD OF THE
LOW OVERNIGHT. SOME HIGH CLOUDS TO MOVE ACROSS THE AREA THIS
EVENING...WITH THE SFC PRES GRADIENT TIGHTENING SO EXPECT WINDS TO
STAY UP A BIT. THETA-E PUSH INTO THE WESTERN CWA BY LATE
TONIGHT...MAY ALLOW FOR SOME ISOLATED SHOWERS AND THUNDERSTORMS TO
PUSH INTO THE CWA. MODELS HAVE CONTINUED TO BE SLOWER WITH THE
PUSH OF MOISTURE AHEAD OF THE SYSTEM...SO HAVE BACKED OFF ON
TIMING AND CONFINED POPS MAINLY TO THE WESTERN CWA TOWARD 12Z.

TEMPS SHOULD REMAIN FAIRLY MILD OVERNIGHT WITH INCREASING MOISTURE
AND THE WINDS STAYING UP...THUS HAVE LOWS IN THE MID 50S TO AROUND
60.

.LONG TERM.../SUNDAY THROUGH SATURDAY/
ISSUED AT 312 PM CDT SAT APR 23 2016

VERY ACTIVE WEATHER PATTERN ON TAP THIS WEEK WITH PRECIPITATION
AND SEVERE WEATHER POTENTIAL EXPECTED ON SUNDAY INTO SUNDAY
NIGHT...TUESDAY NIGHT THROUGH THURSDAY...AND THEN OVER NEXT
WEEKEND. THE MAIN CONCERN WAS FOCUSED ON THE SEVERE THREAT SUNDAY
AFTERNOON INTO THE EVENING.

SUNDAY INTO MONDAY...A SLIGHT NEGATIVELY TITLED UPPER LEVEL
TROUGH EJECTS OUT OF THE CENTRAL ROCKIES AND PUSHES ACROSS THE
CENTRAL TO NORTHERN PLAINS THROUGH THE DAY SUNDAY. ASSOCIATED
SURFACE LOW LOOKS TO BE CENTERED OVER SOUTHERN SOUTH
DAKOTA/NORTHERN NEBRASKA BY 00Z MONDAY WITH A WARM FRONT SURGING
NORTHWARD ACROSS THE STATE INTO SOUTHERN MINNESOTA. SOME MID-LEVEL
THETA-E ADVECTION ON THE NOSE OF THE LLJ SHOULD BE ENOUGH TO SPAWN
A FEW SHOWERS/STORMS ACROSS THE WEST DURING THE MORNING SUNDAY.
THE MAIN SHOW WILL BE LATE AFTERNOON INTO THE EVENING OVER MUCH OF
THE FORECAST AREA.

THE GOOD MOISTURE ADVECTION/WAA CONTINUES THROUGH THE DAY AHEAD
OF THE TROUGH/FRONT TO MOVE THROUGH BY SUNDAY NIGHT...BUT FOCUS
REMAINS WEST OF INTERSTATE 35. BEST INSTABILITY REMAINS IN
WESTERN IOWA WITH MUCAPE VALUES TOPPING 400-900 J/KG AND SURFACE
BASED CAPE IN THE 600-1200 J/KG. AGAIN...BEST FOCUS IS WEST OF
I-35. THE SHEAR PRESENT IS MAINLY UNIDIRECTIONAL SUNDAY INTO
SUNDAY NIGHT...WITH THE DEEP LAYER SHEAR RANGING FROM 35 TO 40
KNOTS...0-1KM AND 0-3KM SHEAR BOTH WITHIN THE 20-30 KNOT RANGE BY
00Z MONDAY. STORMS MORE LIKELY TO INITIATE WITHIN THE OAX CWA AND
PUSH EAST INTO THE WESTERN EDGES OF THE CWA BETWEEN 20-23Z...THEN
MOVE ACROSS THE REMAINDER OF THE FORECAST AREA...BUT THE SEVERE
THREAT LOOKS TO WANE AS THE STORMS MOVE EASTWARD THROUGH THE
EVENING HOURS. THE PRIMARY THREATS WILL BE HAIL/WIND IN THE
AFOREMENTIONED LOCATIONS. LOW CONFIDENCE WITH ANY TORNADIC
THREAT...BUT WITH THE DECENT SHEAR PRESENTS...AN ISOLATED THREAT
CANNOT BE COMPLETELY RULED OUT.

TUESDAY INTO THURSDAY...NEXT UPPER LEVEL LOW SLOWLY ROLLS ACROSS
THE REGION TUESDAY NIGHT INTO EARLY THURSDAY AND BRINGS AN
EXTENDED PERIOD OF SHOWERS AND THUNDERSTORMS TO CENTRAL IOWA. THE
GREATEST SEVERE THREAT LOOKS TO BE WEDNESDAY AFTERNOON INTO THE
EVENING AS A SECONDARY LOBE OF VORTICITY AND UPPER LEVEL FORCING
PUNCHES INTO THE SOUTHERN SECTIONS OF THE FORECAST AREA. BRIEF
BREAK IN THE PRECIP WEDNESDAY LOOKS TO ALLOW FOR SOME INSTABILITY
TO BUILD BACK INTO SOUTHERN IOWA. ALBEIT NOT TOO GREAT...BUT
SHEAR VALUES ARE DECENT AND THE FORCING ASSOCIATED WITH THIS
SHORTWAVE IS FAIRLY STRONG TO AT LEAST HAVE SOME CONCERN FOR
SEVERE WEATHER POTENTIAL IN THE SOUTH WEDNESDAY AFTERNOON/EVENING.
HEAVY RAIN IS THE OTHER THREAT WITH PRECIPITABLE WATER VALUES IN
THE 1-1.25 INCH RANGE...WARM LAYER CLOUD DEPTHS AROUND 11KFT...AND
CORFIDI VECTORS SOMEWHAT CONDUCTIVE TO TRAINING.

FRIDAY AND SATURDAY....NEXT SYSTEM BRINGS ANOTHER ROUND OF
THUNDERSTORMS AND EVEN POSSIBLY HEAVY RAIN SATURDAY AFTERNOON INTO
SUNDAY. THE DEEP TROUGH REMAINS OVER THE WESTERN UNITED STATES
LATE IN THE WEEK AND KEEPS THE FORECAST AREA WITHIN SOUTHWEST FLOW
ALOFT.

&&

.AVIATION.../FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING/
ISSUED AT 631 AM CDT SAT APR 23 2016

IFR/LIFR FOG REMAIN WITH AREA OF MVFR STRATUS REPLACING THE DENSE
FOG THE MAIN CONCERN THIS PACKAGE...WIND A BIT LATER TODAY.
OVERNIGHT WIDESPREAD SHALLOW FOG CONTINUES UNTIL 15Z WITH VSBY
IMPROVING SLOWLY ALL SITES AS ST DECK ADVECTS NORTH AND SUNSHINE
WARMS LAYER. SE WINDS INCREASE AFT 18Z WEST TO EAST WITH GRADUAL
VFR CONDITIONS RETURNING ALL AREAS AFT 19-20Z. AFT 00Z MID TO HIGH
CLOUDS RETURN WITH SUSTAINED SOUTH 11-14KT WIND THRU END OF
PERIOD. /REV


&&

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

&&

$$

SHORT TERM...BEERENDS
LONG TERM...PODRAZIK
AVIATION...REV



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