Severe Thunderstorm Warning 140, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
233 PM CDT MON JUL 3 2000

FORECAST PROBLEM WILL BE POPS...

THUNDERSTORMS ALREADY FIRING IN THE WEST WITH ACTIVITY TO STEADILY
SHIFT EAST THROUGH TONIGHT. SURFACE ANALYSIS AT 15Z SHOWED SERIES OF
LOWS ALONG THE FRONT RANGE FROM NORTHEAST WYOMING...SOUTH INTO NORTH
CENTRAL COLORADO. SURFACE DEWPOINTS ARE INTO THE LOWER 70S AS FAR
NORTH AS ANW WITH MODELS UNDERFORECASTING POTENTIAL CAPES FOR THIS
AFTERNOON AND EVENING...WITH 8H THETA-E RIDGE FURTHER WEST THAN
PROGGED. A SEMI-STATIONARY FRONT CURRENTLY ACROSS NORTHWEST KANSAS
THROUGH THE SOUTHERN NEBRASKA PANHANDLE WILL CONTINUE TO LIFT NORTH
OVERNIGHT AND BE THE FOCUS FOR HEAVY RAIN IN PARTS OF NORTH CENTRAL
NEBRASKA AS 8H LOW LEVEL JET STRENGTHENS.

MODELS ARE IN GENERAL AGREEMENT WITH WEST COAST 5H LOW(S) TO
CONTINUE PINWHEELING WITH A SERIES OF WAVES MOVING DOWNSTREAM TO
OVER THE PLAINS THROUGH 48 HOURS. MODELS HANDLING WAVES DIFFERENTLY
WITH ETA APPEARING TO HAVE THE BEST HANDLE ON WAVE MOVING INTO THE
WESTERN HIGH PLAINS AT THIS TIME AND USED IN GOING FORECAST.

A BRANCH OF THE 2H JET WILL STREAK ACROSS NORTHWEST NEBRASKA THIS
AFTERNOON AND EVENING WITH SCATTERED THUNDERSTORMS SOME POSSIBLY
SEVERE THROUGH 03Z IN THE WEST. WATER VAPOR IMAGERY SHOWS WAVE NOW
MOVING INTO NORTHEAST COLORADO TO INCREASE ACTIVITY IN THE WEST
AFTER 4 PM. NEAR MIDNIGHT 8H SOUTH LOW LEVEL JET TO INCREASE TO 40
KNOTS...WITH INTERACTION BETWEEN JETS TO CONTINUE FUELING
THUNDERSTORMS WHICH MOVE INTO THE NORTH CENTRAL. 7H RIDGE SHARPENS
WITH SLOW MOVEMENT NORTHEAST OF ACTIVITY TONIGHT WITH SOME LOCALES
TO SEE UPWARDS TO 2 TO 3 INCHES OF RAINFALL. DRIER AIR INDICATED
BEHIND WAVE TO MOVE THROUGH THE ROCKIES THIS EVENING BUT HANDS TO
THE WEST WITH LOWS MAINLY IN THE 60S TONIGHT. SOME PATCHY FOG
POSSIBLE BY DAYBREAK IN THE RIVER VALLEY.

FOR THE FOURTH MEAN RELATIVE HUMIDITY TO DECREASE IN THE WEST AS THE
7H RIDGE AXIS SHIFTS EAST. THE DRYLINE WILL REMAIN SOUTH ACROSS
WESTERN NEBRASKA INTO WESTERN KANSAS. THE DRYLINE WILL BE THE FOCUS
FOR ADDITIONAL WIDELY SCATTERED THUNDERSTORM DEVELOPMENT AS AFTERNOON
HEATING INCREASES IN AND THE NEXT SHORTWAVE LIFTS NORTHEAST. SOUTH
WINDS WILL CONTINUE TO SURGE MOISTURE NORTH WITH CAPES AROUND 3000
J/KG OVER NORTH CENTRAL BY EVENING AS THE 7H WAVES MOVES NORTHEAST.
THE TIMING OF ACTUAL IMPULSES OF ENERGY WILL BE DIFFICULT TO TIME
WITH LOW POPS INCLUDED EAST OF THE PANHANDLE. HIGH TEMPERATURES TO
REACH INTO THE LOW TO MID 90S.

LITTLE CHANGE SEEN TUESDAY NIGHT INTO WEDNESDAY WITH SURFACE TROUGH
TO EXTEND SOUTHWEST ACROSS CENTRAL NEBRASKA. THE 7H HIGH CENTER WILL
WEAKEN AS STRONGER DISTURBANCE TOPS THE RIDGE AXIS...THEN THE RIDGE
STRENGTHENS AND REBUILDING IN THE WEST. THE DEGREE OF INSTABILITY
IN PLACE EVEN THOUGH MOISTURE IS DECREASING AND WARMING MID LEVEL
TEMPERATURES PROGGED WILL INCLUDE LOW POPS FOR WIDELY SCATTERED
THUNDERSTORM DEVELOPMENT IN THE EVENING.

IN THE EXTENDED THURSDAY THROUGH SATURDAY MOISTURE AVAILABILITY
AND WARM MID LEVEL TEMPERATURES WILL BE IN QUESTION AS SURFACE
BOUNDARY REMAINS OVER THE PLAINS UNTIL SATURDAY...THEN MOVES SOUTH
AND WASHES OUT. WILL ADD A SLIGHT CHANCE FOR THUNDERSTORMS FOR
SATURDAY. LOWS IN THE 60S AND HIGHS IN THE 90S.

.LBF...NONE

TLK