Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 291742
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1142 AM MDT MON SEP 29 2014

.UPDATE...
ISSUED AT 1138 AM MDTM ON SEP 29 2014

HAVE DECIDED TO ISSUE A FLOOD WATCH FOR PARTS OF NORTHEASTERN
WYOMING AND WESTERN SOUTH DAKOTA THAT WILL BE IN EFFECT THROUGH
TUESDAY MORNING. WIDESPREAD RAIN...LOCALLY HEAVY...IS EXPECTED TO REDEVELOP
OVER PARTS OF NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA
TONIGHT. THE EXCESSIVE RAINFALL MAY RESULT IN THE FLOODING OF
SMALL CREEKS AND STREAMS TONIGHT INTO TUESDAY MORNING.

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
ISSUED AT 231 AM MDT MON SEP 29 2014

08Z SURFACE ANALYSIS HAD LOW PRESSURE OVER EASTERN CO AND HIGH
PRESSURE OVER THE NORTHERN PLAINS. LOW LEVEL NORTHEASTERLY
BOUNDARY LAYER FLOW AS A RESULT. WATER VAPOR SHOWED UPPER LOW
SPINNING OVER NORTHEAST NV/NORTHWEST UT WITH A COUPLE OF
SHORTWAVES WRAPPING AROUND IT...ONE OVER SOUTHWEST SD AND ANOTHER
OVER SOUTH CENTRAL WY. INITIAL WAVE CAUSING CLUSTER OF ELEVATED
CONVECTION OVER CWA AT THE MOMENT WITH NEXT CLUSTER OVER SOUTHEAST
WY...ALL HEADING TO THE NORTH/NORTH-NORTHWEST. MODELS IN GOOD
AGREEMENT WITH EVOLUTION OF THIS SYSTEM.

TODAY THROUGH TUESDAY AFTERNOON...UPPER LOW WILL SPIN NORTHEAST
WRAPPING UP QUITE TIGHTLY OVER THE CWA 12Z TUESDAY AND THEN RACING
NORTHEAST INTO EASTERN ND TUESDAY AFTERNOON. FORCING AHEAD OF IT
WILL BE QUITE PRONOUNCED WITH SUSTAINED UPPER LEVEL DIVERGENCE ON
NOSE OF 110KT JET STREAK. LOW LEVEL FLOW BECOMES INCREASINGLY STRONG
AS SURFACE LOW OVER EASTERN CO DEEPENS AND HEADS NORTH
TONIGHT...STACKING UNDER LOW OVER CWA TUESDAY. SUSTAINED 850-700MB
THETA-E ADVECTION AS WELL AS STRONG ISENTROPIC LIFT WILL GENERATE
WAVES OF SHRA/TSRA OVER THE AREA THROUGH TUESDAY AFTERNOON. HEAVIEST
RAIN SHOULD FALL TONIGHT/EARLY TUESDAY WHEN DEEP LAYER UPSIDENCE
MAXIMIZED. 0.5-1.5 INCHES RAIN LIKELY TO FALL OVER MUCH OF THE
CWA...EXCEPT PERHAPS OVER THE FAR EAST WHEN DRY SLOW MAY DEVELOP
LATER TONIGHT/TUESDAY. LOCAL 1.5-2.5 INCH AMOUNTS LIKELY OVER FAR
NORTHEAST WY/FAR WESTERN SD...ESPECIALLY NEAR THE BLACK HILLS WHERE
UPSLOPE ENHANCEMENT OCCURS. GIVEN ANTECEDENT DRY WEATHER...TIME OF
YEAR...AND EXPECTED SOAKING NATURE OF RAINS...WILL FORGO ANY HYDRO
HEADLINES. EXPECT GUSTY WINDS AHEAD OF AND BEHIND LOW...POSSIBLY
REACHING ADVISORY CRITERIA TUESDAY. TEMPERATURES WILL BE FALL-LIKE
WITH THE SUSTAINED PRECIPITATION...BUT NEAR NORMAL OVER SOUTH
CENTRAL SD. FINALLY...CAPE/SHEAR MAY BE SUFFICIENT FOR A COUPLE OF
STRONG/ISOLATED SEVERE STORMS SNEAKING INTO THE FAR SOUTH LATE
THIS AFTERNOON/EARLY THIS EVENING.

TUESDAY NIGHT...SYSTEM QUICKLY MOVES AWAY BUT IT WILL LEAVE CYCLONIC
FLOW/MOISTURE IN IT/S WAKE. LEFTOVER -SHRA EXPECTED.

&&

.LONG TERM...WEDNESDAY THROUGH SUNDAY
ISSUED AT 231 AM MDT MON SEP 29 2014

CYCLONIC FLOW WILL CONTINUE OVER THE REGION WEDNESDAY WITH SOME
SHOWERS POSSIBLE AS A SECONDARY UPPER WAVE ROUNDS THE BASE OF THE
BROAD TROUGH. A COOLER AIRMASS WILL ADVECT AS THE BACKSIDE OF THE
TROUGH PUSHES INTO THE UPPER MIDWEST. UPPER RIDGING WILL BUILD
ACROSS THE WESTERN CONUS FOR THE SECOND HALF OF THE WEEK...WITH
NORTHWEST FLOW REMAINING OVER THE NORTHERN PLAINS. THIS WILL KEEP
DRIER WEATHER ACROSS THE AREA ALONG WITH TEMPERATURES WILL BELOW
SEASONAL AVERAGES.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z TUESDAY
ISSUED AT 1103 AM MDT MON SEP 29 2014

MVFR/IFR CONDITIONS WILL CONTINUE THROUGH TONIGHT AND
INTO TUESDAY MORNING AS A STRONG STORM SYSTEM SLOWLY CROSSES THE
REGION. THIS SYSTEM WILL CONTINUE TO BRING WIDESPREAD
SHOWERS/ISOLATED STORMS TO THE AREA. IFR VSBY IS EXPECTED WITH THE
HEAVIER PRECIP.

&&

.HYDROLOGY...
ISSUED AT 1132 AM MDT MON SEP 29 2014

A LARGE LOW PRESSURE SYSTEM WILL BRING WIDESPREAD RAIN TO PARTS
OF NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA TODAY THROUGH
TUESDAY MORNING. THERE MAY BE A BREAK IN THE RAIN OVER SOME AREAS
THIS AFTERNOON...BUT WIDESPREAD RAIN IS EXPECTED TO REDEVELOP THIS
EVENING...AND CONTINUE THROUGH TUESDAY MORNING.

SOME AREAS OF THE BLACK HILLS AND FAR SOUTHWESTERN SOUTH DAKOTA
HAVE ALREADY RECEIVED 1 TO 2 INCHES OF RAIN. ANOTHER 1 TO 2 INCHES
OF RAIN...WITH LOCAL AMOUNTS AS HIGH AS 3 INCHES ARE POSSIBLE OVER
PARTS OF NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA TONIGHT
THROUGH TUESDAY MORNING. THE EXCESSIVE RAINFALL MAY CAUSE FLOODING
OF SMALL CREEKS AND STREAMS. THE RAIN WILL TAPER OFF FROM SOUTH
TO NORTH DURING THE DAY ON TUESDAY.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...FLOOD WATCH THROUGH TUESDAY MORNING FOR SDZ001-002-012-013-
     024>031-041-042-072>074.

WY...FLOOD WATCH THROUGH TUESDAY MORNING FOR WYZ056-057-071.

&&

$$

UPDATE...10
SHORT TERM...HELGESON
LONG TERM...13
AVIATION...POJORLIE
HYDROLOGY...10





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