Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 021718
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1218 PM CDT SUN AUG 2 2015

.UPDATE...
ISSUED AT 1211 PM CDT SUN AUG 2 2015

BUMPED UP DEWPOINTS A COUPLE OF DEGREES ALONG/SOUTH OF
I80...ESPECIALLY IN KNOWN AREAS WHERE DEWPOINTS WILL REMAIN
ELEVATED. THIS RESULTS IN HEAT INDEX VALUES 100-104 IN SOME SPOTS
THIS AFTERNOON ALONG/SOUTH OF I80. HAVE ADDED MENTION TO THE HWO
FOR NOW.

COLD FRONT IS A LITTLE SLOWER TO MOVE INTO THE REGION. HIRES
MODEL SUITES OF HRRR/NMM/ARW CONTINUE TO INDICATE POTENTIAL
CONVECTIVE DEVELOPMENT BY 19-21Z...PERHAPS IN THE PLATTE RIVER
VALLEY. EXTREME INSTABILITY HAS ALREADY DEVELOPED WITH SPC
MESOANALYSIS INDICATING AROUND 4000 J/KG OF CAPE. WIND SHEAR WILL
ALSO BE IN THE 30 KNOT RANGE...WHICH SHOULD BE SUPPORTIVE OF SOME
LARGE HAIL IF STORMS DEVELOP. BECAUSE OF THE EXTREME
INSTABILITY...WILL HAVE TO WATCH FOR MICROBURSTS TOO WITH
DOWNDRAFT CAPES PUSHING 1700-1900. WILL MAINTAIN A 20 PERCENT
CHANCE FOR NOW UNTIL WE SEE DEVELOPMENT.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 354 AM CDT SUN AUG 2 2015

CHANCE FOR THUNDERSTORMS AND WARM TEMPERATURES TODAY...THEN OFF AND
ON STORM CHANCES THROUGH TUESDAY...ARE THE PRIMARY FORECAST CONCERNS.

SCATTERED THUNDERSTORMS POPPED UP EARLY THIS MORNING JUST AHEAD OF
MID LEVEL WAVE DROPPING SOUTHEAST THROUGH EASTERN NEBRASKA AND
SOUTHWEST IOWA AS PER WATER VAPOR AND RAP ANALYSIS. THIS WAVE WILL
TRACK EAST OF OUR CWA EARLY IN THE DAYLIGHT HOURS...WITH SUBSIDENCE
BEHIND WAVE KEEPING MUCH OF THE REST OF THE MORNING DRY.

ANOTHER SHORTWAVE IN THE NORTHERN PLAINS INTO THE NORTHERN GREAT
LAKES IS FORECAST TO SWEEP SOUTHEAST LATER TODAY...WITH SURFACE
REFLECTION IN THE FORM OF A FRONT/WIND SHIFT SETTLING INTO NORTHEAST
NEBRASKA THIS AFTERNOON. SURFACE DEW POINTS NEAR OR ABOVE 70F AHEAD
OF THIS BOUNDARY ARE EXPECTED TO POOL IN EASTERN NEBRASKA AND
WESTERN IOWA DURING PEAK HEATING. CONVERGENCE ALONG BOUNDARY SHOULD
BE ENOUGH TO GET AT LEAST ISOLATED THUNDERSTORMS FIRING IN UNSTABLE
ATMOSPHERE CHARACTERIZED BY MUCAPES OVER 2500 J/KG. MEANWHILE
MODERATE MID LEVEL FLOW WILL HELP GENERATE NEAR 40KT OF BULK SHEAR
WITH VECTORS NORMAL TO SURFACE CONVERGENCE...SUGGESTING DISCRETE AND
ROTATING STORMS ARE LIKELY...SUPPORTING HAIL AND WIND POTENTIAL.
ONLY MARGINAL RISK IN SPC OUTLOOK...AND CAN NOT ARGUE GIVEN
EXPECTED SCANT COVERAGE. INITIATION LOOKS TO BE FARTHER NORTH THAN
PREVIOUS MODEL RUNS WITH LATER ARRIVAL OF FRONT...MOSTLY LIKELY
FIRING NEAR OR SOUTH OF A WAYNE TO ALBION LINE BETWEEN 3 AND 4 PM.
EXPECT ISOLATED TO SCATTERED STORMS TO PROGRESS SOUTH THROUGH THE
REST OF THE AFTERNOON INTO THE EVENING WITH FRONTAL BOUNDARY
BEFORE EXITING SOUTHEAST NEBRASKA AND SOUTHWEST AROUND MIDNIGHT
WHEN LAST OF 850 MOISTURE PLUME FINALLY DROPS SOUTH.

AHEAD OF FRONT...TEMPERATURES ARE EXPECTED WELL INTO THE 90S
ESPECIALLY IF CLOUD COVER FROM MORNING CONVECTION DISSIPATES AS
EXPECTED. WILL LIKELY SEE SOME HEAT INDICES TOPPING 100 FOR A COUPLE
OF HOURS THIS AFTERNOON.

SHOULD SEE A DRY PERIOD AFTER MIDNIGHT TONIGHT...BUT LOWERING
PRESSURES IN THE HIGH PLAINS WILL DRAW 850 MOISTURE BACK NORTH
RATHER QUICKLY BY LATER MONDAY MORNING AS NORTHWEST MID LEVEL FLOW
CONTINUES. WILL KEEP OUR SMALL POPS FOR OUR WESTERN CWA DURING THAT
TIME PERIOD...WITH CHANCES/COVERAGE GRADUALLY INCREASING MONDAY
AFTERNOON...BUT ESPECIALLY OVERNIGHT AND TUESDAY AS MAGNITUDE OF
MOISTURE RETURN INCREASES. WILL MAINTAIN 30 TO 50 PERCENT STORM
CHANCES DURING THE DAY TUESDAY. SEVERE THREAT SHOULD BE MINIMAL THEN
AS INSTABILITY REMAINS WEAK DUE TO MUCH COOLER SURFACE
TEMPERATURES.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 354 AM CDT SUN AUG 2 2015

UNSETTLED WEATHER PATTERN WITH OCCASIONAL RAIN/STORM CHANCES WILL
CONTINUE THROUGH MUCH OF THE REST OF THE WEEK. MID LEVEL RIDGE IS
FORECAST TO REMAIN FROM TEXAS WEST TO THE SOUTHWESTERN STATES AT
LEAST THROUGH THURSDAY...KEEPING STORM TRACK ROLLING FROM THE
CENTRAL/NORTHERN ROCKIES ACROSS THE PLAINS. SEVERAL SHORTWAVES COULD
TRIGGER CONVECTION AT JUST ABOUT ANY TIME...WITH MORE POTENT WAVES
MOVING THROUGH OUR AREA WEDNESDAY DURING THE DAY AND THURSDAY
NIGHT AS PER ECMWF/GFS. WE SHOULD REMAIN ON THE COOL SIDE OF
SURFACE FRONTAL SYSTEM...SO INSTABILITY PROGS SUGGEST SEVERE
CHANCE WILL BE MINIMAL OVERALL WITH TEMPERATURES REMAINING IN THE
70S AND 80S MUCH OF THE WEEK.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1211 PM CDT SUN AUG 2 2015

VFR CONDITIONS THROUGH THE PERIOD AS A COLD FRONT MOVES INTO THE
AREA. THERE IS A 20 PERCENT CHANCE THAT STORMS COULD DEVELOP BY
19-21Z. THESE STORMS WOULD LIKELY BE SOUTH OF THE KOFK TAF
SITE...BUT COULD AFFECT KLNK/KOMA 23-01Z TIME FRAME. BECAUSE OF
LOW CERTAINTY ON DEVELOPMENT...WILL KEEP OUT OF THE TAF FOR
NOW...BUT WILL UPDATE FORECAST IF STORMS INDEED DEVELOP AND WOULD
AFFECT THOSE TAF SITES. WIND SHIFT WILL ALSO BE AFFECTING
KOMA/KLNK FROM SOUTHWEST TO NORTHWEST BY 23-01Z AS WELL.

&&

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

$$

UPDATE...DEWALD
SHORT TERM...DERGAN
LONG TERM...DERGAN
AVIATION...DEWALD


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