Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 311801
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
101 PM CDT FRI JUL 31 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 334 AM CDT FRI JUL 31 2015

THE CHANCE FOR THUNDERSTORMS AND SEVERE POTENTIAL LATER TODAY AND
SATURDAY...AND WARM TEMPERATURES SUNDAY...ARE THE PRIMARY FORECAST
CONCERNS.

PESKY AREA OF CONVECTION FIRED IN NORTHEAST NEBRASKA LATE LAST
EVENING AND HAS PERSISTED INTO THIS MORNING WHILE DRIFTING INTO EAST
CENTRAL NEBRASKA AND WEST CENTRAL IOWA. STORMS WERE FIRING IN AREA
OF LIFT ON RIGHT ENTRANCE REGION MID LEVEL JET JUXTAPOSED WITH
RIBBON OF HIGHER 850 MOISTURE WHERE INHIBITION WAS WEAK. STORMS WERE
DIMINISHING AS THEY DRIFTED SOUTHEAST AWAY FROM MOISTURE AND INTO
MORE INHIBITION. SHORT RANGE HI-RES MODELS SUGGEST MOST OF THIS
ACTIVITY WILL BE GONE BY OR SHORTLY AFTER SUNRISE.

MEANWHILE WEAK FRONTAL BOUNDARY IN SOUTHEAST SOUTH DAKOTA IS
FORECAST TO PROGRESS TOWARD INTERSTATE 80 THIS AFTERNOON. SOUTHERLY
FLOW AHEAD WILL DRAW/KEEP MID 60S DEW POINTS IN OUR AREA...AND WITH
RELATIVELY COOL MID LEVEL TEMPERATURES...INSTABILITY WILL INCREASE
WITH AFTERNOON HEATING AS CAP WEAKENS. THERE IS GOOD CONSENSUS FROM
HI-RES MODELS THAT SCATTERED STORMS WILL FIRE BY 20Z OR SO NEAR
CONVERGENCE ZONE ALONG FRONTAL BOUNDARY. COVERAGE IS STILL IN
QUESTION...BUT COMBINATION OF INSTABILITY AND MODEST SHEAR SUGGESTS
AN ISOLATED HAIL/WIND EVENT WILL BE POSSIBLE.

EXPECT CONVECTION TO DIMINISH THIS EVENING WITH LOSS OF HEATING.
HOWEVER WEAK SHORTWAVE AND ATTENDANT INCREASE IN LOW LEVEL JET IN AN
INCREASINGLY MOIST ENVIRONMENT SUGGESTS THERE IS AT LEAST A SLIGHT
CHANCE FOR CONVECTION AFTER MIDNIGHT FROM NORTH CENTRAL INTO
SOUTHEAST NEBRASKA. AND THOSE COULD LINGER INTO SATURDAY MORNING.
BUT BETTER CHANCES COME SATURDAY AFTERNOON WHEN PERHAPS OUR BEST
CHANCE FOR SEVERE WILL DEVELOP. SURFACE DEW POINTS ARE FORECAST INTO
THE MID AND UPPER 60S FOR MUCH OF THE CWA AHEAD OF FRONTAL BOUNDARY
TIED TO SHORTWAVE AND SURFACE LOW TRACKING ACROSS EASTERN SOUTH
DAKOTA. WIND FIELDS INCREASE AT THIS TIME AS WELL...CREATING BULK
SHEAR IN THE 35 TO 45KT RANGE. IF MORNING CONVECTION REMAINS
SPARSE...EXPECT AFTERNOON HEATING TO PRODUCE MOST-UNSTABLE CAPES
TOPPING 2500J/KG ALONG/AHEAD OF SURFACE FRONT...FOCUSING GREATEST
POTENTIAL IN NORTHEAST NEBRASKA INITIALLY. SUFFICIENT INSTABILITY
AND SHEAR WILL EXIST FOR ORGANIZED STORMS AND SUPERCELLS WITH
POTENTIAL FOR HAIL/WIND. THIS AREA WILL LIKELY GROW UPSCALE INTO AN
MCS...TRACKING SOUTHEAST THROUGH WESTERN IOWA AND EASTERN NEBRASKA
SATURDAY EVENING AND OVERNIGHT.

STORMS SHOULD BE EAST OF OUR AREA SUNDAY MORNING...WITH WESTERLY LOW
LEVEL WIND COMPONENT AND DRIER AIR IN ITS WAKE. 850 TEMPS BY SUNDAY
AFTERNOON ARE FORECAST INTO THE MID AND UPPER 20S UNDER A DECENT
MIXING REGIME...SUGGESTING HIGHS SUNDAY AFTERNOON WILL RISE WELL
INTO THE 90S MOST AREAS.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 334 AM CDT FRI JUL 31 2015

AN UNSETTLED WEATHER PATTERN WILL PERSIST THROUGH MUCH OF NEXT WEEK
AS NORTHWEST FLOW REMAINS ACROSS THE NORTHERN PLAINS INTO THE OHIO
VALLEY. OUR AREA WILL REMAIN ON THE SOUTHWEST FRINGE OF THE
STRONGEST MID LEVEL FLOW...WITH SEVERAL SHORTWAVES MARCHING THROUGH
THE PLAINS. MEANWHILE...PERSISTENT SURFACE FRONTAL BOUNDARY WILL
OSCILLATE NORTH/SOUTH WITH THE PASSAGE OF EACH WAVE...PROVIDING LOW
LEVEL CONVERGENCE FOR CONVECTION EACH DAY. GFS AND ECMWF BOTH
SUPPORT THIS PATTERN...WITH VARYING DEGREES/TIMING OF SHORTWAVE
INTRUSION INTO OUR AREA. SO WILL CONTINUE OUR CURRENT FORECAST TREND
OF A CHANCE FOR STORMS EACH PERIOD DURING THE LONGER RANGE
PERIOD...WITH TEMPERATURES SLIGHTLY COOLER GIVEN PERSISTENT EASTERLY
WIND COMPONENT IN LOW LEVEL FLOW. THERE IS SOME INDICATION
WESTERN RIDGE WILL PUSH FAR ENOUGH EAST LATER IN THE PERIOD TO
PUSH CONVECTION TO OUR NORTHEAST...BUT WILL WAIT FOR FURTHER MODEL
CONSISTENCY BEFORE REMOVING POPS FOR THURSDAY.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1251 PM CDT FRI JUL 31 2015

VSBY SATL TREND IS SHOWING SPOTTY CU DEVELOPING ALONG AN
INSTABILIY AXIS FROM ABOUT KHJH TO TO KHNR THIS AFTN AND EXPECT
TSRA DEVELOPMENT WITHIN THE NEXT COUPLE HOURS. THE TSRA ACTIVITY
THOUGH SHOULD GENERALLY BE ISOLD IN NATURE...BUT CANNOT TOTALLY
DISCOUNT KOMA/KLNK BEING AFFECTED. THUS HAVE INCLUDED LATE
AFTN/EARLY EVENING TEMPO GROUPS. OTHERWISE VFR PREVAILING THE
REMAINDER OF THE FCST PD.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$

SHORT TERM...DERGAN
LONG TERM...DERGAN
AVIATION...DEE



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