Storm Prediction Center Severe Risk For November 29, 2016
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1154 PM CST MON NOV 28 2016
VALID 291200Z – 301200Z
…THERE IS AN ENH RISK OF SVR TSTMS ACROSS ERN LA…MUCH OF
MS…PARTS OF SRN TN…
…THERE IS A SLGT RISK OF SVR TSTMS FROM THE SABINE RIVER NEWD INTO
SRN KY…
…THERE IS A MRGL RISK OF SVR TSTMS FROM THE CENTRAL GULF COAST
NEWD INTO KY…
…SUMMARY…
SEVERE STORMS ARE EXPECTED ACROSS PARTS OF THE LOWER MISSISSIPPI
VALLEY AND ADJACENT GULF COASTAL AREAS…AND EXTENDING NORTHEASTWARD
INTO TENNESSEE AND KENTUCKY. THE THREAT SHOULD PEAK TUESDAY EVENING
AND OVERNIGHT. STORMS MAY BE ACCOMPANIED BY TORNADOES…HAIL…AND
DAMAGING WIND…WITH A FEW STRONG TORNADOES POSSIBLE.
…SYNOPSIS…
THE UPPER AIR PATTERN WILL FEATURE A STATIONARY UPPER LOW CENTERED
OVER THE NORTHERN PLAINS AND UPPER MS VALLEY…WITH BROAD AREA OF
CYCLONIC FLOW FROM THE ROCKIES ACROSS THE SOUTHERN PLAINS AND LOWER
MS VALLEY AND INTO THE LOWER GREAT LAKES. EARLY IN THE DAY…A
LEADING SHORTWAVE TROUGH WILL DISSIPATE AS IT MOVES FROM THE OH
VALLEY ACROSS THE NORTHEASTERN STATES WITH SLIGHT HEIGHT RISES TO
THE SOUTHWEST. HOWEVER…BY LATE TUESDAY EVENING…A LARGER SHORTWAVE
TROUGH WILL ROTATE EASTWARD ACROSS THE SOUTHERN PLAINS AND WILL
APPROACH THE MS RIVER INTO WEDNESDAY MORNING.
AT THE SURFACE…A LOW PRESSURE TROUGH WILL EXTEND FROM THE MIDDLE MS
VALLEY SOUTHWARD TOWARD THE SABINE RIVER BY 00Z…WITH A SECONDARY
SURFACE LOW MOVING FROM AR ACROSS TN…KY…AND INTO SOUTHERN OH BY
WEDNESDAY MORNING. EXTENDING SOUTHWESTWARD FROM THE LOW WILL BE AN
INTENSIFYING COLD FRONT WHICH WILL SWEEP EASTWARD TO AN EASTERN KY
TO SOUTHEAST LA LINE BY WEDNESDAY MORNING. AHEAD OF THIS FRONT…
RAPID WARM AIR ADVECTION WILL OCCUR IN THE LOW-LEVELS DURING THE DAY
AS A WARM FRONT PUSHES NORTHWARD…WITH 850 MB FLOW INCREASING TO 50
KT BY 00Z. A MOISTENING AND DESTABILIZING AIR MASS WILL MATERIALIZE
ACROSS THE WARM SECTOR WITH MID 60S F DEWPOINTS APPROACHING THE
SOUTHERN BORDER OF TN BY EVENING AND NEAR 70 F DEWPOINTS ACROSS LA
AND MS.
LIFT ALONG THE COLD FRONT…WITH INCREASING SHEAR PROFILES AND
FAVORABLE LARGE-SCALE SUPPORT SHOULD ALLOW FOR A CORRIDOR OF
SIGNIFICANT SEVERE WEATHER POTENTIAL ACROSS THE ENHANCED RISK AREA.
…EASTERN AR AND NORTHERN LA…MS…NORTHERN AL…TN…KY…
SUBSTANTIAL LOW-LEVEL MOISTURE IS ALREADY IN PLACE ACROSS THE
CENTRAL GULF COAST WITH DEWPOINTS NEAR 70 F OVER LA AS OF MONDAY
EVENING. AS THE WARM FRONT SHIFTS NORTHWARD DURING THE DAY…
MOISTENING WILL OCCUR AND SOME MODELS SUCH AS THE WRF-ARW AND THE
HRRR SHOW SCATTERED THUNDERSTORMS DEVELOPING IN THE WARM ADVECTION
ZONE FROM NEAR THE SABINE RIVER EASTWARD ACROSS LA AND PERHAPS INTO
CENTRAL MS. IF THIS OCCURS…THESE WOULD LIKELY TAKE THE FORM OF
SUPERCELLS AS SHEAR PROFILES WILL BE QUITE STRONG ALOFT…WITH
MODERATE SRH OF 200-300 M2/S2 PRESENT ALONG THE WARM FRONT. HAIL AND
A TORNADO ARE CONDITIONALLY POSSIBLE WITH THE EARLY/MIDDAY ACTIVITY.
IN THE WAKE OF ANY EARLY ACTIVITY…AND PRECEDING THE COLD FRONT…
MOISTENING AND DESTABILIZATION WILL CONTINUE…WITH FORECAST
SOUNDINGS SHOWING A SMALL CAPPING INVERSION AROUND 800 MB. THIS
SHOULD ENSURE THAT WARM SECTOR DEVELOPMENT IS FOCUSED ALONG THE COLD
FRONT…WHICH WILL ALSO LIMIT THE NUMBER OF STORMS INITIALLY AND BE
FAVORABLE FOR SUPERCELLS. INSTABILITY WILL BE STRONGER THAN THE
PREVIOUS DAY…AND SHEAR WILL REMAIN VERY STRONG WITH HODOGRAPHS
FAVORING TORNADIC SUPERCELLS AS WELL AS HAIL AND WIND. THE
LIKELIHOOD OF DISCRETE SUPERCELLS…AMPLE MOISTURE…AND VERY STRONG
SHEAR ALL SUGGEST A COUPLE TORNADOES MAY BE STRONG.
SOME DIFFERENCES EXIST IN TERMS OF HOW FAR EAST OR WEST THE COLD
FRONT DEVELOPMENT WILL TAKE PLACE…BUT GENERAL MODEL CONSENSUS IS
NEAR THE MS RIVER ALONG THE AR/MS BORDER…AND EXTENDING
SOUTHWESTWARD THROUGH THE EVENING ACROSS EASTERN LA AND OVER MUCH OF
MS. THE INITIAL DEVELOPMENT AROUND 00Z MAY MOVE FROM EASTERN
AR/NORTHERN MS INTO MIDDLE TN AND EVENTUALLY SOUTHERN KY WITH A
TORNADO AND WIND THREAT. FURTHER DEVELOPMENT IS ALSO EXPECTED AROUND
03Z FROM CENTRAL LA INTO CENTRAL MS…EITHER JUST AHEAD OF THE FRONT
OR IN A PRE-FRONTAL CONFLUENCE LINE. HERE…DEWPOINTS WILL BE IN THE
UPPER 60S F…AND INSTABILITY WILL BE ON THE ORDER OF 1000 J/KG WHICH
WILL CLEARLY BE SUFFICIENT FOR SUPERCELLS AND A FEW TORNADOES GIVEN
THE AMPLE MOISTURE.
..JEWELL/LEITMAN.. 11/29/2016