National Weather Outlook
Soggy weather continues across the middle part of the country with consecutive days of shower and thunderstorm activity. Some of the thunderstorms over the next several days could be strong to severe with heavy rainfall and flooding potential. Also note the rain showing up across Florida. This particular system could make for an interesting second half of week along the southeastern U.S. coastline.
Rogue Tropical System?
Now this is interesting. Extended model runs continue to indicate a random area of low pressure developing by midweek east of Florida. The forecast brings the area of low pressure near the Carolina Coast by AM Thursday before moving inland AM Friday near Savannah, Georgia. Heavy rains and gusty winds look to be the primary threat with this particular system. While not necessarily a significantly strong storm system, it’s an interesting trend.
Atlantic Hurricane Records: Earliest Formation for each Category
Keep in mind that the official Atlantic Hurricane Season is from June 1st – November 30th. On average, this is when nearly 97% of all Atlanctic based tropical systems have formed. The list below shows the earliest formation recorded for each category and note the earliest Substropical Storm, Tropical Storm and Category 1 Hurricane formation on record all developed in January.
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Severe Threat Monday
…SUMMARY…
A FEW SEVERE THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND EVENING
FROM CENTRAL AND NORTHERN KANSAS INTO SOUTHERN IOWA AND NORTHERN
MISSOURI TO WEST-CENTRAL ILLINOIS. A FEW SEVERE STORMS ARE ALSO
EXPECTED ACROSS SOUTHEAST NEW MEXICO INTO WEST AND SOUTHWEST TEXAS
THIS AFTERNOON AND EVENING. LARGE HAIL AND DAMAGING WINDS WILL BE
THE MAIN THREATS.
…SRN HIGH PLAINS THROUGH TONIGHT…
A SRN STREAM SHORTWAVE TROUGH WILL PROGRESS EWD FROM JUST OFF THE
SRN CA COAST TO SRN AZ/NM BY THE END OF THE PERIOD…AS AN EMBEDDED
SUBTROPICAL SPEED MAX EJECTS NEWD TOWARD SW TX. THIS LARGER-SCALE
PATTERN WILL CONTRIBUTE TO AT LEAST WEAK CYCLOGENESIS ACROSS E/SE
NM. IN RESPONSE…LOW-LEVEL MOISTURE WILL CONTINUE TO SPREAD NWWD
UP THE RIO GRANDE AND PECOS VALLEYS…WITH 100 MB MEAN MIXING RATIOS
NEAR 12 G/KG AND BOUNDARY LAYER DEWPOINTS INTO THE MID 60S AS FAR NW
AS DRT-SANDERSON AS OF 12Z. THE COMBINATION OF LOW-LEVEL
MOISTURE…RESIDUAL MIDLEVEL LAPSE RATES…AND DAYTIME HEATING
SHOULD SUPPORT MLCAPE VALUES NEAR 1500 J/KG.
SOME WEAK CONVECTION IS ONGOING OVER SE NM/SW TX…AND ADDITIONAL
STORM FORMATION APPEARS LIKELY BY EARLY AFTERNOON AS MOISTURE
INCREASES IN THE ZONE OF ASCENT BENEATH THE LEFT EXIT REGION OF THE
JET ALOFT. THE BACKGROUND PATTERN OF ASCENT AND MOISTENING ALOFT
WILL TEND TO LIMIT MIDLEVEL LAPSE RATES IN TIME…AND CONTRIBUTE TO
WIDESPREAD CONVECTION BY TONIGHT INTO THE TX SOUTH PLAINS REGION.
PRIOR TO THE WIDESPREAD OVERTURNING…MORE DISCRETE CELLS WILL BE
POSSIBLE ACROSS SE NM AND SW TX /ESPECIALLY NEAR THE DAVIS
MOUNTAINS/. THE STORM ENVIRONMENT WILL BE SUPPORTIVE OF SUPERCELLS
WITH A RISK FOR LARGE HAIL/DAMAGING WINDS…AND PERHAPS A BRIEF
TORNADO.
…CENTRAL/NRN KS TO SRN IA/NRN MO THROUGH TONIGHT…
AN MCV OVER N CENTRAL KS THIS MORNING WILL TRANSLATE NEWD TO SE NEB
THIS AFTERNOON…AND THEN CONTINUE EWD OVER IA TONIGHT. THE MCV
TRACK WILL CORRESPOND ROUGHLY WITH A SLOW-MOVING SURFACE FRONT.
DEBRIS CLOUDS FROM OVERNIGHT CONVECTION WILL TEND TO SLOW SURFACE
HEATING BEFORE THE CLOUDS THIN BY EARLY AFTERNOON. A SLOW INCREASE
IN LOW-LEVEL MOISTURE WILL OCCUR THROUGH THE DAY IN CONJUNCTION WITH
HORIZONTAL ADVECTION AND SOME DOWNWARD MIXING OF MOISTURE THIS
MORNING. THE REMNANTS OF A STEEP MIDLEVEL LAPSE RATE PLUME WILL
EXTEND NEWD OVER KS…THOUGH CONVECTIVE OVERTURNING IN THE PAST 12
HOURS HAS RESULTED IN SOME STABILIZATION ALOFT. THE NET RESULT OF
THESE COMPETING PROCESSES SHOULD STILL BE A CORRIDOR OF POTENTIALLY
MODERATE BUOYANCY ALONG THE FRONT THIS AFTERNOON /MLCAPE VALUES OF
1500-2000 J PER KG/.
THUNDERSTORM DEVELOPMENT IS EXPECTED BY MID-LATE AFTERNOON IN
ASSOCIATION WITH THE REMNANT MCV…AND AS CONVECTIVE INHIBITION
WEAKENS IN THE ZONE OF ASCENT ALONG THE SURFACE FRONT. LOW-LEVEL
SHEAR AND BUOYANCY WILL BE SUFFICIENT FOR SOME STORM
ORGANIZATION…BUT A PRONOUNCED WEAKNESS IN THE FLOW NEAR 300 MB
WILL NOT BE SUPPORTIVE OF PERSISTENT SUPERCELLS. THUS…THE MAIN
SEVERE CONCERNS WILL BE A FEW DAMAGING WIND AND LARGE HAIL EVENTS
WITH MULTICELL CLUSTERS AND/OR OUTFLOW-DRIVEN LINE SEGMENTS.
Severe Threat Tuesday
…SUMMARY…
SCATTERED STRONG TO SEVERE THUNDERSTORMS STILL APPEAR POSSIBLE
TUESDAY ACROSS PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS.
…SYNOPSIS…
THERE APPEARS LITTLE CHANGE FROM THE PREVIOUS OUTLOOK FOR THIS
PERIOD CONCERNING THE GENERAL LARGE-SCALE UPPER PATTERN EVOLUTION.
THE STRONGER BELT OF MID-LATITUDE WESTERLIES STILL APPEARS LIKELY TO
UNDERGO AMPLIFICATION ACROSS THE NORTH CENTRAL AND NORTHEAST
PACIFIC. MODELS CONTINUE TO INDICATE THAT A VIGOROUS MID/UPPER
TROUGH ON THE LEADING EDGE OF THIS REGIME WILL BEGIN SPLITTING AFTER
PROGRESSING INLAND ACROSS THE PACIFIC NORTHWEST COAST BY 12Z
TUESDAY. AS ONE SIGNIFICANT IMPULSE PIVOTS AROUND THE EASTERN
PERIPHERY OF AN EMBEDDED MID-LEVEL LOW…THE CENTER OF CIRCULATION
IS FORECAST TO REDEVELOP EAST NORTHEASTWARD INTO SOUTHERN ALBERTA BY
12Z WEDNESDAY. AT THE SAME TIME…ANOTHER SIGNIFICANT IMPULSE IS
EXPECTED TO BEGIN TO DIG SOUTH SOUTHEASTWARD ACROSS OREGON/NORTHERN
CALIFORNIA…TOWARD LARGE-SCALE TROUGHING WITHIN A WEAKER SOUTHERN
BRANCH OF MID-LATITUDE WESTERLIES…ACROSS SOUTHERN
CALIFORNIA/NORTHERN BAJA INTO THE SOUTHERN PLAINS.
MEANWHILE…A SHORT WAVE IMPULSE ON THE LEADING EDGE OF THIS LATTER
REGIME…INITIALLY IN PHASE WITH THE SUBTROPICAL STREAM…IS
FORECAST TO PIVOT NORTHEAST OF THE SOUTHERN ROCKIES. THIS IS
EXPECTED TO OCCUR AS AN UPSTREAM IMPULSE APPROACHES THE SOUTHERN
CALIFORNIA/NORTHERN BAJA COAST…AND BECOMES INCREASINGLY IN PHASE
WITH THE SUBTROPICAL STREAM.
WITHIN THE SUBTROPICAL STREAM…DOWNSTREAM OF THESE
DEVELOPMENTS…HIGH-LEVEL TROUGHING APPEARS LIKELY TO GRADUALLY
SHIFT NORTHEAST OF THE SOUTHEASTERN GULF OF MEXICO/CARIBBEAN REGION.
THIS MAY BE ACCOMPANIED BY THE DEVELOPMENT OF A SURFACE LOW TO THE
EAST OF THE FLORIDA PENINSULA. THE PRESENCE OF THESE FEATURES MAY
CONTINUE TO IMPACT BOUNDARY LAYER MOISTENING OVER A LARGE PORTION OF
THE NORTHERN GULF OF MEXICO. RICH TROPICAL MOISTURE MAY REMAIN
CONFINED TO THE VICINITY OF THE MEXICAN GULF COAST…AS WELL AS
PORTIONS OF THE FLORIDA PENINSULA. HOWEVER… FURTHER MOISTENING IS
PROBABLE ON DEEP SOUTHERLY FLOW THROUGH MUCH OF THE PLAINS…WITH
SEASONABLY MODEST MOIST CONTENT PERSISTING WITHIN A PLUME ALONG A
QUASI-STATIONARY FRONTAL ZONE EXTENDING FROM THE NORTHERN MID
ATLANTIC INTO THE UPPER MIDWEST.
…CENTRAL AND SOUTHERN HIGH PLAINS…
ONLY MINOR CHANGES TO THE SEVERE WEATHER PROBABILITIES HAVE BEEN
MADE. THE LATEST MODEL RUNS ARE NOT SUPPORTIVE OF INCREASING
PROBABILITIES. IF ANYTHING…CONFIDENCE MAY BE A BIT LOWERED.
IT STILL APPEARS THAT LARGE-SCALE FORCING…DOWNSTREAM OF THE LEAD
IMPULSE EMERGING FROM THE SOUTHERN INTERMOUNTAIN REGION…MAY BE
SUPPORTING CONSIDERABLE CONVECTIVE DEVELOPMENT BY THE BEGINNING OF
THE FORECAST PERIOD ACROSS PARTS OF THE CENTRAL AND SOUTHERN HIGH
PLAINS. THIS ACTIVITY MAY LINGER…WHILE GRADUALLY SPREADING
EASTWARD DURING THE DAY…AS THE APPROACHING UPPER TROUGH GRADUALLY
PIVOTS NORTHEAST AND NORTH OF THE SOUTHERN ROCKIES.
STRONGEST DESTABILIZATION…ASSOCIATED WITH DAYTIME HEATING BENEATH
RELATIVELY COOL MID-LEVEL AIR ASSOCIATED WITH THE UPPER
TROUGH…PROBABLY WILL BECOME FOCUSED BETWEEN A DEVELOPING
BAROCLINIC ZONE ASSOCIATED WITH DIFFERENTIAL HEATING /ACROSS THE
TEXAS SOUTH PLAINS INTO NORTHEAST NEW MEXICO/ AND THE DRYLINE TO ITS
SOUTHWEST. MIXED LAYER CAPE MAY BE SOMEWHAT MODEST…ON THE ORDER
OF 1000 J/KG…BUT AN INCREASING WESTERLY COMPONENT TO THE 30-40 KT
CYCLONIC MID-LEVEL FLOW /WITH THE PASSAGE OF THE UPPER TROUGH AXIS/
IS EXPECTED TO CONTRIBUTE TO INCREASINGLY FAVORABLE VERTICAL SHEAR
FOR SUPERCELL STRUCTURES DURING THE LATE AFTERNOON AND EVENING.
Severe Threat Wednesday
…SUMMARY…
SCATTERED SEVERE STORMS APPEAR POSSIBLE LATE WEDNESDAY AFTERNOON AND
EVENING ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS.
…SYNOPSIS…
AMPLIFICATION OF THE MID-LATITUDE WESTERLIES ACROSS THE NORTH
CENTRAL AND NORTHEASTERN PACIFIC THROUGH THE WESTERN U.S. APPEARS
LIKELY TO CONTINUE DURING THIS FORECAST PERIOD. WITHIN THIS
REGIME…THE ELONGATING SOUTHERN PORTION OF A SPLITTING SHORT WAVE
IMPULSE IS FORECAST TO CONTINUE DIGGING JUST INLAND OF THE PACIFIC
COAST. DOWNSTREAM SHORT WAVE RIDGING WILL PROBABLY BUILD ACROSS THE
CENTRAL AND SOUTHERN ROCKIES…INTO ADJACENT PORTIONS OF THE CENTRAL
AND SOUTHERN PLAINS…IN THE WAKE OF A SHORT WAVE TROUGH EXPECTED TO
EMERGE FROM THE SOUTHERN INTERMOUNTAIN REGION ON TUESDAY.
THIS IMPULSE…WHICH IS EXPECTED TO REACH THE CENTRAL PLAINS BY 12Z
WEDNESDAY…MAY TEND TO SHIFT MORE NORTHWARD THAN EASTWARD THROUGH
THE MID MISSOURI VALLEY…WITH A MID-LEVEL HIGH CENTER INITIALLY
FAIRLY PROMINENT NEAR THE CENTRAL APPALACHIANS…TO THE NORTH OF A
DEVELOPING CYCLONE OFF THE SOUTH ATLANTIC COAST /ASSOCIATED WITH
UPPER TROUGHING IN THE SUBTROPICAL STREAM/. AS THIS OCCURS…MODELS
INDICATE THAT LOW PRESSURE WILL CONTINUE TO DEEPEN WITHIN THE
NORTHERN PORTION OF LEE SURFACE TROUGHING SHIFTING OUT OF THE
NORTHERN AND CENTRAL HIGH PLAINS…TOWARD THE LOWER PLAINS. A
GRADUAL FURTHER MOISTENING OF LOWER LEVELS AHEAD OF THE TROUGH AXIS
IS EXPECTED TO PROCEED ON MODERATE SOUTHERLY LOW-LEVEL FLOW.
…CENTRAL AND SOUTHERN PLAINS…
CONVECTIVE CLOUD COVER AND PRECIPITATION CURRENTLY APPEARS LIKELY TO
LIMIT BOUNDARY LAYER DESTABILIZATION AHEAD OF THE NORTH
NORTHEASTWARD PROGRESSING SHORT WAVE IMPULSE. IN THE WAKE OF THIS
FEATURE…HOWEVER…IT DOES APPEAR THAT SURFACE HEATING… BOUNDARY
LAYER MOISTENING /SURFACE DEW POINTS IN THE LOWER TO MID 60S/…AND
AT LEAST MODEST STEEPENING OF MID-LEVEL LAPSE RATES WILL CONTRIBUTE
TO MODERATE MIXED LAYER CAPE ALONG A SHARPENING DRY LINE BY LATE
AFTERNOON. DUE TO THE LACK OF WARMER ELEVATED MIXED LAYER
AIR…CAPPING SHOULD NOT BE PROHIBITIVE TO CONVECTIVE DEVELOPMENT.
SO…DESPITE WEAKER MID/UPPER FORCING FOR UPWARD VERTICAL
MOTION…THE INITIATION OF AT LEAST WIDELY SCATTERED DISCRETE STORMS
APPEARS PROBABLE. AS 30-40+ KT CYCLONIC MID-LEVEL FLOW TAKES ON A
MORE WESTERLY COMPONENT IN THE IMMEDIATE WAKE OF THE UPPER
IMPULSE…CONTRIBUTING TO STRONG DEEP LAYER SHEAR…THERE APPEARS A
WINDOW OF OPPORTUNITY FOR A FEW SUPERCELLS CAPABLE OF PRODUCING
LARGE HAIL…LOCALLY DAMAGING WIND GUSTS…PERHAPS A COUPLE OF
TORNADOES.
IT REMAINS UNCLEAR HOW DEEP INTO THE EVENING THIS SEVERE THREAT WILL
PERSIST…AS MID-LEVELS TEND TO WARM…AND THE DRYLINE RETREATS
WESTWARD TOWARD THE HIGHER PLAINS.
Severe Threat Saturday?
Interestingly, the Storm Prediction Center has already issued a thunderstorm outlook across parts of the Plains for Saturday. Another storm system looks to develop late week/early weekend near the Four Corners Region and bring another potential round of strong to severe thunderstorms to the parts of the Plains. Stay tuned!
…DISCUSSION… UNCERTAINTY WITHIN THE MEDIUM RANGE MODEL OUTPUT…CONCERNING AN AMPLIFYING SHORT WAVE TROUGH EMERGING FROM A STRONGER BELT OF MID-LATITUDE WESTERLIES…DIGGING JUST INLAND OF THE PACIFIC COAST AT THE OUTSET OF THE FORECAST PERIOD…APPEARS TO BE DECREASING. IN GENERAL…IT APPEARS THAT AN EMBEDDED MID-LEVEL LOW WILL EVOLVE AS THIS IMPULSE GRADUALLY TURNS ACROSS THE SOUTHERN GREAT BASIN…TOWARD THE FOUR CORNERS REGION…LATE THIS WEEK. PHASING WITH THE SUBTROPICAL STREAM DOES APPEAR POSSIBLE…BEFORE THIS SYSTEM BEGINS ACCELERATING EAST NORTHEASTWARD. GUIDANCE CONTINUES TO INDICATE SATURDAY AS THE MOST LIKELY DAY THAT THIS IMPULSE EMERGES FROM SOUTHERN INTERMOUNTAIN REGION…CONTRIBUTING TO A DEEPENING SURFACE CYCLONE OVER THE CENTRAL HIGH PLAINS. INCREASING LARGE-SCALE FORCING FOR ASCENT…STRENGTHENING VERTICAL SHEAR…AND THE CONTINUING PRESENCE OF MOIST…POTENTIALLY UNSTABLE AIR PROBABLY WILL BE SUFFICIENT TO SUPPORT ORGANIZED SEVERE CONVECTION…INCLUDING SUPERCELLS…ACROSS THE CENTRAL AND SOUTHERN PLAINS. AS THIS UPPER IMPULSE…AND ASSOCIATED SURFACE CYCLONE…PROGRESS EASTWARD IN SUBSEQUENT DAYS…SEVERE PROBABILITIES REMAIN BELOW 15 PERCENT AT THIS TIME DUE TO INCREASING UNCERTAINTIES/DECREASING PATTERN PREDICTABILITY.
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3 Day Precipitation Outlook
According to NOAA’s HPC, the 3 day precipitation forecast from AM Monday to AM Thursday suggests heavier pockets of rain across parts of the Plains. Thanks to some convective precipitation, rainfall tallies through AM Thursday could be as much as 2″ to 4″ or more.
7 Day Precipitation Outlook
Ongoing shower and thunderstorm potential across the midsection of the nation could produce as much as 3″ to nearly 5″ or more of rain by early next week. Keep in mind that some of the heavy rain could come in a fairly short amount of time, so flooding may be a concern.
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