Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 032036
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
336 PM CDT SUN MAY 3 2015

.SYNOPSIS...
ISSUED AT 330 PM CDT SUN MAY 3 2015

A VERY CHALLENGING DAY OF WARM SEASON IMPACTS HAVE BEEN
OVER OUR REGION TODAY...AS A PERSISTENTLY ACTIVE MCV HAS SLOWLY
TRAVERSED OUR CWA FROM WEST TO EAST. THE SLOW MOVEMENT ALLOWED IT TO
MAINTAIN CONTACT WITH THE PLUME OF HIGHER PWAT VALUES AROUND 1 INCH.
WHILE INSTABILITY HAS NOT BEEN HIGH...ENOUGH MUCAPE (500 J/KG)...AS
BEEN IN PLACE TO SUPPORT SMALL AND SHALLOW UPDRAFTS WITH OCCASIONAL
LIGHTNING. RAINS OVER THE NORTHERN 1/2 HAVE SEEN...WHERE STORMS
CROSSED THROUGH...ANYWHERE FROM 0.15 TO LIKELY A BIT OVER 1 INCH.
TEMPERATURES IN THE COLD POOL FROM THIS ACTIVITY HAVE HELD IN THE
LOWER 60S...WHILE JUST OUTSIDE/WEST HAVE ROCKETED INTO THE UPPER 70S
TO LOWER 80S. WHILE MUCH OF IOWA IS CLEAR AND WARMING AHEAD OF THE
COMING COLD FRONT...OUR EYES ARE FOCUSED ON ANOTHER CLUSTER OF
ELEVATED STORMS IN EASTERN NEBRASKA. THIS SHOWS THE LOCATION OF THE
NEXT SHORT WAVE...AND SHOULD BE THE NEXT TRIGGER FOR CONVECTION OVER
OUR CWA TONIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 330 PM CDT SUN MAY 3 2015

TODAY AND MONDAY... OUR CWA WILL REMAIN ON THE NOSE OF
MOISTURE TRANSPORT AND MUCAPE ADVECTION THROUGH THE EARLY MORNING
HOURS MONDAY. THE MAIN QUESTION FOR THE FORECAST FOR TONIGHT THROUGH
TUESDAY WILL BE TO HOW MUCH OF A DEGREE THE LLJ VEERS OR
NOT...BETWEEN ROUNDS OF STORMS. WITH THE DEVELOPING WESTERN
TROF...AND LITTLE REASON FOR INTENSE ORGANIZED/SEVERE STORMS...IT
SEEMS A SCENARIO WHERE WINDS ALOFT WILL BACK QUICKLY AFTER PASSING
ROUNDS OF STORMS EXIT. THIS SETS THE STAGE FOR REPEATING ROUNDS OF
NON SEVERE STORMS...WITH HEAVY RAIN POSSIBLY RESULTING IN THE
COMING DAYS.

TONIGHT...SURFACE BASED CONVECTION SHOULD FIRE TO OUR
NORTHWEST...OVER SOUTHERN MN/NORTHERN IA...AND MOVE EAST TO
SOUTHEAST WITH TIME. MID LEVEL WESTERLIES SHOULD CARRY STORMS
EAST...WHILE MOISTURE INFLUX FROM THE SOUTHWEST ALLOWS THEM TO BUILD
MOST AGGRESSIVELY ON THE SOUTHERN FLANK. I SEE SEVERAL DRY HOURS
THIS EVENING...FOLLOWED BY THE MAIN ACTIVITY INITIALLY MOVE NORTH OF
THE CWA...BUT BY MID EVENING...THIS CONVECTION SHOULD DROP
SOUTH...WITH THE MOST INTENSE UPDRAFTS LOCATED IN NORTHEASTERN IOWA
BEFORE 1 AM...AND OVER EASTERN/SOUTHEASTERN IOWA AND WESTERN
ILLINOIS AFTER THAT TIME. THIS IS DUE TO THE EXPECTED VEERING LLJ
ALOFT...BUT IN ANY CASE...COVERAGE APPEARS AT LEAST HIGH END
LIKELY...IF NOT CATEGORICAL FOR MOST LOCATIONS AFTER 10 PM. RAINFALL
TONIGHT SHOULD BE WIDESPREAD 0.25 TO 1.25...BUT AS TODAY SHOWED
US...THE ATMOSPHERE IS CAPABLE OF AMOUNTS HIGHER THAN THAT...AND
SOME LOCATIONS MAY SEE OVER 1.5 TONIGHT.

CONDITIONS MONDAY SYNOPTICALLY SUPPORT CHANCE
POPS...HOWEVER...MESOSCALE TRENDS WILL CERTAINLY RULE THE
DAY...AS CONVECTION LIKELY WANES IN THE MID MORNING HOURS...OR
SETTLES SOUTH AND EAST OF THE CWA. BACKING WINDS ALOFT MAY
CERTAINLY ALLOW FOR SOME SCATTERED ACTIVITY THROUGH THE DAY ON TOP
OF THE COLD POOL/STALLED FRONT. IN ANY CASE...THE NEXT SHORT WAVE
DUE TO RIDE OVER THE FRONT SHOULD ARRIVE BY MID AFTERNOON...AND
WITH BACKING WINDS THROUGH 850MB FORECAST BY ALL GUIDANCE...AND
DIVERGENCE ALOFT...IT SEEMS LIKELY POPS ARE ONCE AGAIN WARRANTED
BY MID AFTERNOON. SINCE THIS WILL ARRIVE AT PEAK HEATING...A LOW
RISK FOR AN ISOLATED SEVERE STORM CANNOT BE RULED COMPLETELY OUT.
HOWEVER...ORGANIZED SEVERE STORMS SEEM VERY UNLIKELY GIVEN THE MID
SUMMER LIKE WEAK FLOW.

LIKE TODAY...CHALLENGING TEMPERATURES ARE EXPECTED...WITH HIGHS IN
THE LOWER 70S NORTH TO AROUND 80 SOUTH A LEAST ERROR FORECAST...BUT
FAR FROM CONFIDENT.
ERVIN

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 330 PM CDT SUN MAY 3 2015

OVERVIEW...THE POLAR UPPER JET WILL WILL SHIFT INTO NORTHERN CANADA
THROUGH THE WEEK. UPPER-LEVEL RIDGING BUILDING IN ACROSS THE CENTRAL
U.S. BEHIND THE POLAR JET WILL RESULT IN A SIGNIFICANT CHANGE TO A
MUCH MORE MOIST ATMOSPHERE. MEAN 850-300MB WINDS WILL SLOWLY VEER
FROM WESTERLY TO SOUTHWESTERLY DURING THE EARLY PORTION OF THE WEEK.
PWAT VALUES WILL BE ABOVE AVERAGE DURING THIS TIME.

MONDAY EVENING AND NIGHT...ANOTHER POTENTIAL CONVECTIVELY INDUCED PV
ANOMALY WILL ORIGINATE OVER THE CENTRAL ROCKIES AND PROPAGATE OVER
THE DVN CWA PROVIDING LIFT AND A GOOD CHANCE FOR SHOWERS/STORMS. THE
GREATEST COVERAGE IS PROBABLY GOING TO OCCUR BETWEEN 6PM-12AM.
INSTABILITY WILL BE DECREASE THROUGH THIS PERIOD STARTING NEAR 1500
J/KG IN THE EARLY EVENING AND FALLING BELOW 1000 J/KG BY MIDNIGHT.

A FEW STORMS MAY BE STRONG WITH SMALL HAIL AND WIND GUSTS OVER 40
MPH BUT BY AND LARGE SEVERE WEATHER IS NOT EXPECTED. THE MAIN STORY
WILL BE THE HEAVY RAIN POTENTIAL.

MOISTURE...PWAT VALUES ARE GOING TO BE RELATIVELY HIGH BETWEEN 1.25-
1.50 INCHES BUT THE NAEFS PLACES THIS IN THE 85TH-90TH PERCENTILE OR
NEAR 1.5 STANDARD DEVIATIONS ABOVE THE MEAN FOR THE BEGINNING OF
MAY. RELATIVELY DRY ANTECEDENT CONDITIONS SHOULD LIMIT OVERALL FLOOD
POTENTIAL EVEN FOR AREAS THAT RECEIVE THE HEAVIEST RAIN.

FORWARD PROPAGATING CORFIDI VECTORS SUGGEST SLOW EAST-NORTHEAST
MOVING MULTICELL STORMS AT ABOUT 20-25 MPH. 500MB WINDS WILL BE
NEARLY PARALLEL TO THE SFC-850MB BOUNDARY WHICH MEANS THE POTENTIAL
FOR TRAINING OF SHOWERS/STORMS IS THERE.

RAINFALL AMOUNTS...MOST AREAS WILL RECEIVE BETWEEN 0.25 TO 0.75
INCHES BUT THERE WILL LIKELY BE A ONE TO TWO COUNTY WIDE ZONE OF
HIGHER AMOUNTS OVER 1 INCH...AND THERE COULD BE A NARROW BAND OF 1-2
INCHES. THE PLACEMENT MAY CHANGE SLIGHTLY BUT THE HIGHWAY 30
CORRIDOR APPEARS TO BE THE MOST LIKELY AREA FOR THE HEAVIEST RAIN.

TUESDAY...A WARM FRONT WILL LIFT INTO THE NORTHERN CWA TUE AFTN.
DROPPED TEMPS DOWN BELOW CONSENSUS ACROSS THE NE THIRD OF THE CWA.
WENT AS COOL AS MID 60S NEAR FREEPORT BUT STILL HAVE LOWER 80S IN
THE FAR SOUTH. SCT SHOWERS/STORMS ARE POSSIBLE ESPECIALLY IN THE
MORNING AND EARLY AFTN.

WEDNESDAY...VERY WARM...HIGHS IN THE LOWER 80S AS THE SOUTHERLY FLOW
INCREASES AND THE RIDGING CONTINUES TO BUILD.

THURSDAY AND FRIDAY....TEMPS WILL REMAIN IN THE UPPER 70S TO LOWER
80S. AN ORGANIZED UPPER-LEVEL WILL EJECT OUT OF THE CENTRAL ROCKIES
BUT REMAIN WELL TO THE WEST OF THE MIDDLE TO UPPER MISSISSIPPI
VALLEY REGION...OVER NEBRASKA AND THE DAKOTAS.

CHANCES FOR SCT SHOWER/STORMS WILL INCREASE ESPECIALLY DURING PEAK
HEATING TIME. DISTANCE FROM THE CENTER OF THE MID-LEVEL LOW WILL
KEEP SYNOPTIC/QG FORCING RELATIVELY WEAK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 700 AM CDT SUN MAY 3 2015

MAINLY VFR CONDITIONS ARE EXPECTED THROUGH 00Z/04 WITH DECAYING
CONVECTION THROUGH 18Z/03. ALTHOUGH SMALL...THE POTENTIAL IS THERE
FOR A SHRA AND MAYBE A TSRA TO AFFECT A TAF SITE WITH A BRIEF
PERIOD OF MVFR CONDITIONS. AFT 00Z/04 A COLD FRONT WILL SLOWLY
MOVE INTO EASTERN IOWA. NEW CONVECTION IS EXPECTED TO DEVELOP WITH
CONDITIONS SLOWLY DECAYING TO MVFR THROUGH 12Z/04.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...ERVIN
SHORT TERM...ERVIN
LONG TERM...UTTECH
AVIATION...08



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