Area Forecast Discussion
Issued by NWS Rapid City, SD

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901
FXUS63 KUNR 050848
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
248 AM MDT THU MAY 5 2016

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT
ISSUED AT 244 AM MDT THU MAY 5 2016

08Z SURFACE ANALYSIS HAD MODEST SOUTHERLY FLOW OVER THE CWA.
UPPER RIDGE SLOWLY MOVING EAST INTO THE PLAINS STATES WITH WARM
AIR ADVECTION CI SPILLING INTO THE CWA. UPPER TROUGH/LOW CURRENTLY
OFF THE CA COAST THE MAIN CONCERN THIS FORECAST PERIOD.

TODAY...UPPER/THERMAL RIDGE PEAKS OVER THE AREA WITH TEMPERATURES
WELL INTO THE 80S. 500J/KG MLCAPE WILL DEVELOP ON THE SD
PLAINS...BUT MLCIN WILL BE TOO STRONG WITH SUBSIDENCE ALOFT FOR TSRA.

TONIGHT...LOW LEVEL JET DEVELOPS OVER CENTRAL SD...BUT THETA-E
ADVECTION WEAK. PERHAPS SOME ACCAS WILL FORM...BUT PRECIPITATION
SHOULD BE PRECLUDED BY RATHER DRY SUB CLOUD LAYERS.

FRIDAY...UPPER RIDGE MOVES EAST AS COLD FRONT DROPS SOUTH INTO THE
CWA. MOISTURE POOLING ALONG BOUNDARY DURING PEAK
HEATING...ESPECIALLY OVER SOUTHERN HALF OF CWA...RESULTS IN 500-
1000J/KG MLCAPE AND WEAK 0-6KM BULK SHEAR. MLCIN WEAK ENOUGH TO
ALLOW TSRA TO DEVELOP IN THE AFTERNOON AHEAD OF SHORTWAVE MOVING
ACROSS CO INTO WY...WHICH IS AHEAD OF UPPER LOW SPINNING OVER CA/NV.
TEMPERATURES WILL BE TRICKY WITH CLOUD COVER/PRECIPITATION COVERAGE
AFFECTING EVENTUAL READINGS.

FRIDAY NIGHT...TSRA ACTIVITY QUIETS DOWN SOME WITH -SHRA BECOMING
MORE PREVALENT UNDER FAIRLY MOIST EAST/NORTHEAST BOUNDARY LAYER
FLOW. FORCING AHEAD OF UPPER LOW WILL BE FOCUSED OVER SOUTHWEST
THIRD OF CWA WHERE HIGHEST POPS WERE PAINTED. LOWS WILL BE NEAR
GUIDANCE.

.LONG TERM...SATURDAY THROUGH WEDNESDAY
ISSUED AT 244 AM MDT THU MAY 5 2016

A STRONG UPPER LOW BEGINS TO MOVE OUT OF THE DESERT SOUTHWEST
INTO THE CENTRAL ROCKIES BY SUNDAY. THEN IT SLOWLY DRIFTS EASTWARD
ACROSS THE CENTRAL PLAINS ON MONDAY AND TUESDAY. ANOTHER LOWS
PUSHES SOUTHEASTWARD INTO THE NORTHERN ROCKIES ON MONDAY. AFTER
THIS POINT THE MODELS BEGIN TO DISAGREE. THE ECMWF SEEMS TO
COMBINE THE TWO UPPER LOWS INTO ONE SYSTEM...THEN DEEPENS THE NEW
LOW AS IT SLOWLY MOVES ACROSS SOUTH DAKOTA WRAPPING PLENTY OF
MOISTURE AROUND IT. THE GFS SOLUTION PUSHES THE FIRST LOW INTO THE
GREAT LAKES REGION WHILE THE NEW LOW DEEPENS OVER THE FORECAST
AREA AND SLOWLY MOVES EAST ACROSS SOUTH DAKOTA. REGARDLESS OF THE
SOLUTION AND THE MODEL DIFFERENCES...BOTH MODELS INDICATE A WET
PATTERN WITH DAILY CHANCES FOR SHOWERS AND SEASONAL TEMPERATURES
THROUGH THE EXTENDED PERIOD.

&&

.AVIATION...FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT
ISSUED AT 244 AM MDT THU MAY 5 2016

VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIOD.

&&

.FIRE WEATHER...
ISSUED AT 244 AM MDT THU MAY 5 2016

THIS AFTERNOON/S MINIMUM RELATIVE HUMIDITY WILL DROP TO THE MID
TEENS OVER NORTHEAST WY TO THE 20S OVER CENTRAL SD. SOUTHERLY WINDS
WILL AVERAGE 10 TO 20 MPH. FIRE WEATHER HEADLINES WILL NOT BE
NEEDED GIVEN THESE CONDITIONS.

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...HELGESON
LONG TERM...MLS
AVIATION...MLS
FIRE WEATHER...HELGESON



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