FXUS63 KOAX 132030
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
ISSUED BY NATIONAL WEATHER SERVICE HASTINGS NE
330 PM CDT WED JUL 13 2011
.DISCUSSION...THE PATTERN ALOFT FEATURED AN UPPER LOW PRESSURE
SYSTEM IN THE PACIFIC NORTHWEST...HIGH PRESSURE RIDGE FM THE
SOUTHERN PLAINS NORTH ALONG THE MISSOURI RIVER. THIS RESULTED IN A
GENERAL SOUTHWEST FLOW REGIME ACROSS NEBRASKA INTO SOUTHWEST IOWA.
WEAK SHORTWAVE TROUGHS EMBEDDED IN THE FLOW WERE TRANSLATING
NORTHEAST INTO CENTRAL AND EASTERN NEBRASKA AND HAVE GENERATED
ISOLATED TO SCATTERED CONVECTION. AT THE SURFACE...WARM FRONTAL
BOUNDARY WAS LOCATED ALONG THE NEBRASKA AND KANSAS STATE LINE.
CONVECTION SO FAR THIS AFTN HAS BEEN LOCATED IN CENTRAL AND
NORTHERN NEBRASKA WITH ADDITIONAL DEVELOPMENT ALONG THE HIGH
PLAINS REGION. THE WRF IS THE MOST ROBUST WITH CONVECTION THIS
EVENING AND TONIGHT THAN OTHER MODELS...AND GIVEN TRENDS BEST CHCS
APPEAR ACROSS THE WESTERN AND NORTHERN PORTIONS OF THE CWA.
INSTABILITY PARAMETERS INDICATE MU CAPES OF 1000 TO 2000 J/G
TONIGHT WITH THE HIGHER VALUES ALONG THE WESTERN BORDER...WITH
DEEP LAYER SHEAR VALUES INCREASING TO AROUND 30KTS OVERNIGHT. AN
ISOLATED SEVERE STORM IS POSSIBLE TONIGHT...WITH STORMS CAPABLE OF
PRODUCING LARGE HAIL...DAMAGING WINDS AND LOCALLY HEAVY RAINFALL
WITH PCPN WATER VALUES NEAR TWO INCHES.
THE WARM FRONTAL BOUNDARY WILL CONTINUE TO LIFT NORTH TONIGHT...BUT
MODELS SUGGEST LOW CLOUDS WILL HOVER AROUND THE MISSOURI RIVER AREA
INTO THURSDAY MORNING. COULD SEE SOME LIGHT DRIZZLE OR PATCHY FOG
UNDER THE STRATUS BUT DO NOT THINK THIS WILL BE WIDESPREAD OR
SIGNIFICANT ENOUGH TO MENTION IN THE FORECAST ATTM. MODELS INDICATE
SOME WEAK ISENTROPIC LIFT ON THE 315K SURFACE THURSDAY MORNING INTO
EARLY AFTN AND HAVE MAINTAINED A LOW POP ACROSS MOST AREAS INTO THE
AFTN...BUT DO THINK A GENERAL DRYING TREND/IMPROVING CONDITIONS WILL
EXIST IN THE AFTN AS FRONT CONTINUES TO LIFT NORTH AND LOW CLOUDS
BREAK.
THURSDAY TEMPS WILL BE DEPENDENT UPON INSOLATION AND HAVE SOME
CONCERNS ALONG THE MISSOURI RIVER AND WESTERN IOWA WHERE CLOUDS MAY
HOLD LONGER. HAVE ATTEMPTED TO GO WITH SOME MIDDLE GROUND HERE BUT
MAXES WILL BE TOO WARM IF CLOUDS HOLD AND MAY NOT BE WARM ENOUGH IF
CLOUDS BREAK SOONER.
THE UPPER RIDGE AXIS CONTINUES TO EXPAND NORTH THURSDAY NIGHT AND
SHORTWAVE ENERGY RIDING AROUND THE RIDGE MAY GENERATE CONVECTION
...WITH NORTHERN NEB ON THE EDGE OF THE ACTIVITY. HAVE BUFFERED IN
SOME LOW POPS FOR NOW AND WITH ORIENTATION OF THE LLVL JET THE
MAIN ACTIVITY SHLD FOCUS IN THE EASTERN DAKOTAS AND MIDWEST
REGION.
THE HEAT COMMENCES ON FRIDAY WITH BUILDING RIDGE AND TEMPS ARE
EXPECTED TO REACH THE 90S...WITH HEAT INDICES CLIMBING NEAR 100
DEGREES WITH THE HIGH DPS/HUMIDITY EXPECTED. FRIDAY NIGHT LOOKS TO
SEE A SIMILAR REGIME TO THURSDAY NIGHT WITH WAVE RIDING NORTH FM
HIGH PLAINS TOWARD NORTHEAST NEBRASKA AND WILL MAINTAIN A LOW POP
IN THE NORTH. IF THINGS CAN GO IN THIS AREA...SEVERE STORMS ARE
POSSIBLE.
BY THE WEEKEND INTO NEXT WEEK THE UPPER RIDGE SETTLES IN ACROSS THE
INTERIOR CONUS WITH HOT AND DRY CONDITIONS/HIGH HUMIDITY SETTLING IN
FOR SEVERAL DAYS. HEAT INDICES WILL TOP THE CENTURY MARK AND
HEADLINES FOR THE EXCESSIVE HEAT WILL LIKELY BE NEEDED...AND WILL
CONTINUE TO MENTION HEAT POTENTIAL IN HWO.
&&
.AVIATION...18Z TAFS. EAST WINDS RESULTING IN UPSLOPE CONTINUE TO
CAUSE LOW CLOUDS TO OCCUR OVER THE AREA. EXPECT THE CLOUDS TO
BREAK AS THE DAYTIME HEATING ERODES THEM AWAY A BIT. NONE THE
LESS...AFTER THE MVFR CEILINGS BREAK...EXPECT CUMULUS CLOUDS TO
DEVELOP BUT IN THE VFR RANGE. THEN AS A SHORT WAVE EJECTS OVER THE
AREA OVERNIGHT SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP SO
WILL MENTION A CHANCE OF THUNDER IN TAF AFTER MIDNIGHT. EXPECT IFR
LOW CLOUDS AND AREAS OF FOG TO REDEVELOP AFTER
MIDNIGHT...ESPECIALLY TOWARDS SUNRISE AND PERSIST SEVERAL HOURS
INTO THE DAY THURSDAY.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
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