Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/25/20
Area Forecast Discussion
National Weather Service Birmingham AL
722 PM CDT Tue Mar 24 2020
For 00Z Aviation.
/Updated at 0237 PM CDT Tue Mar 24 2020/
This afternoon through Wednesday.
Ingredients are coming together for a very active period of severe
weather this evening for areas along and north of I-20. The airmass
across central Alabama has been baking under a warm low level
southwest flow all day with temperatures reaching the upper 70s to
lower 80s. Despite heating, surface dewpoints been steady in the
lower to middle 60s throughout the day, indicating a fairly deep
moist layer near the surface. 12Z JAN/BMX soundings show capping
inversion just below 700mb, which has kept a lid on convection
through the early afternoon. Latest radar scans show convection
breaking out over northern MS where surface based CAPE was near
1500 J/kg. Becoming increasingly concerned about tornado potential
over northwest counties of central Alabama. Hi-res models are
showing more discrete supercell development over northeast MS
later this afternoon. Forecast 0-3km EHI values across the
northwest counties are also increasing with current runs of the
HRRR model. The discrete cells should organize into a broken line
of storms by 9 or 10 pm with a lower threat of tornadoes, but
still showing rotating cells within the line. Extended severe
threat until midnight due to the threat of ongoing severe storms
across east Alabama. Everything should be winding down quickly by
midnight as low level flow weakens veers and weakens.
The remaining showers and thunderstorms should exit east Alabama
by sunrise Wednesday. Decreasing clouds and slightly cooler
temperatures on Wednesday with highs ranging from the lower 70s
north to lower 80s south.
/Updated at 0350 AM CDT Tue Mar 24 2020/
Wednesday night through Monday.
Post-frontal, dry conditions will be in place across the Southeast
Wednesday night as the surface low moves eastward into the Atlantic
while the east to west oriented cold front continues southward
through the Florida Peninsula. Weak, cool air advection and
northwesterly flow will allow temperatures to decrease into the
upper 40s northeast and 50s elsewhere on Thursday morning before
rising sharply after sunrise as a 593dam ridge builds over the Gulf
of Mexico. A surface high will develop over the Mid-Atlantic and may
produce weak cool air damming over northern parts of Georgia which
would keep temps a few degrees cooler across our northeast.
Nonetheless, height rises, warm southwesterly low-level flow, and
dry, subsident air will accompany this setup, allowing for afternoon
highs around 15 degrees above average for this time of the year with
temps topping out in the 80s area-wide on Thursday and Friday.
This occurrence would challenge a few of our daily high records
for both days.
Meanwhile, an upper low over the Central US will track towards the
Great Lakes Region on Saturday with a surface front reaching the
Lower Mississippi Valley early Saturday afternoon. Guidance has
trended towards better agreement in a late Saturday frontal passage
across the forecast area, so PoPs were raised during this time frame
with early evening thunderstorms possible before instability wanes
after dark. There are still some uncertainties with this system, but
severe weather is not expected at this time. Cooler temperatures
and a short break in the rain are expected behind the front for
the start of next week, but guidance indicates another system will
approach the area beyond this period.
00Z TAF Discussion.
Added an AMD NOT SKED to all terminals this package. This was due
to a technical issues with data. Most likely will eventually add
some amendments in the next 2 hours.
Convection ahead of a cold front will slowly move into Central
Alabama through 06z. The storms will affect all the northern
terminals in this period. Some of the storms may be severe with
gusty winds, hail and tornadoes. At this time, the terminals have
a tempo for 1sm ts. The storms will move southeastward through the
evening and start to dissipate and pull eastward before impacting
TOI. Ceilings will drop to MVFR as the storms arrive. After the
front, ceilings drop again to IFR and hold there north through
15-18z. Winds will be southwest around 10 kts and gusty then shift
to the northwest at 5-10kts. Some VFR looks likely by afternoon.
Southern sites will have a lesser chance of rain or storms and
then drop to MVFR ceilings.
Scattered to numerous showers and thunderstorms will spread across
north Alabama tonight. Some of the storms could be severe, mainly
along and north of I-20. A weakening band of showers and storms
will push into the southern counties after midnight. A weak cool
front will bring drier and slightly cooler air into central
Alabama on Wednesday. Warmer conditions on Thursday and Friday
with no rain expected. Despite highs in the 80s Thursday and
Friday, afternoon humidity levels will only fall into the 40-50
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 57 73 48 79 59 / 90 10 0 0 0
Anniston 60 74 50 80 60 / 90 10 0 0 0
Birmingham 59 74 52 82 63 / 90 10 0 0 0
Tuscaloosa 60 76 53 84 62 / 90 0 0 0 0
Calera 60 75 52 82 62 / 90 10 0 0 0
Auburn 63 76 54 80 60 / 60 10 0 0 0
Montgomery 65 80 55 86 62 / 50 10 0 0 0
Troy 65 81 56 85 62 / 20 10 0 0 0
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Tue Mar 24 2020
An area of low level moisture will accompany a frontal boundary
across the southeast Michigan overnight. The resulting coverage of
low stratus may prove chaotic at times given recent trends, but
continue to support a generally broken condition during the early-
mid morning hours. Restrictions held in MVFR with some lowering
below 2000 ft possible near daybreak. Warmer air lifting into the
region as flow veers to south/southwest will eventually support a
general clearing trend late morning/early afternoon Wednesday.
For DTW...Lower stratus will exist through the early-mid morning
hours, then increasing likelihood for clearing after 14z-15z.
.DTW THRESHOLD PROBABILITIES...
* High for ceilings at or below 5000 ft tonight. Low Wednesday
Issued at 341 PM EDT Tue Mar 24 2020
Surface high pressure is currently centered over the stable lake
aggregate from the Lake Huron basin southward through central Lake
Erie. No tangible weather to speak of other than varying coverage of
opaque stratus. Model soundings and plan view persecptive show
unidirectional easterly flow in the lowest 5000 ft of the column.
The lack of anticyclonic flow trajectories has really limited any
active lower column subsidence from penetrating downward into the
sub inversion layer and any shot at widespread saturation/cloud
dissipation. Instead the area remains under the effect of residual
cool drainage flow off of the anticyclone to the east. Will continue
to favor a higher sky fraction forecast for the remainder of today.
Uncertainty exists for tonight with regard to cloud forecast. Rap
soundings show fairly convincing signal for loss of saturation with
nightfall. Difficult to outright discount this idea as much of the
cloud north of Metro Detroit is appearing convective from diabatic
heating. South of M 59 cloud is much more laminar and there is a 850-
775mb thermal discontinuity to the south. Models show veering of the
wind directions to more southerly tonight which will allow the weak
frontal feature to push directly into the area. Latest fleeting
thought is that clouds will dissipate somewhat quickly this evening
north of M59, clouds will hold south this evening before lifting
Residual surface high pressure enhanced early by ridging dipole off
Ohio River low pressure will persist over Southeast Michigan for a
good portion of Wednesday. Differential height rises will balloon
into Lower Michigan during the latter half of the day which will
force low level warm advection directly into the area on increased
southwest gradient flow. The warm advection will erode out lingering
sub-inversion saturation and cloud. Expecting rapid loss to any
remaining cloud late Wednesday afternoon and evening.
Strong warm advection collocated with amplifying shortwave will
bring a period of ascent and precipitation to the northern Great
Lakes. The question remains how far south precipitation will fall as
consensus of solutions has been relatively dry for the cwa. The
period of concern for the northern wave precipitation chances is
centered around 12Z Thursday morning. Blended guidance and model QPF
output are a mess. Forecast soundings show a very narrow saturated
layer on elevated front, with pleny of dry air concerns at the
surface. Forecast soundings also show very active midlevel
subsidence indicative of a very strong background for frontolysis
based on rapid evolution of unfavorable jet forcing aloft. Main
narrative is one of a low chance PoP, tied to some potential for
Low confidence portion of the forecast is where exactly
precipitation will be supported along a baroclinic zone that becomes
increasingly organized south of the Michigan border late Thursday
through early Saturday. Pattern recognition and some model data
supports strong subsidence holding locally with frontal zone being
suppressed to the south. Initial jetlet on amplified ridge is
expected to bring an ageostrophic response and wave of low pressure
along the front late Thursday. Blended guidance is again difficult
to work with and too broadbrushed, but consensus calls for main
window for precipitation for some late Thursday night, then waiting
until Saturday night and Sunday. Plenty of time exists to work out
details on storm system amplitude for the weekend.
High pressure remains in control across the Great Lakes as it drifts
east into New England, resulting in calm to light winds. A series of
low pressure system will then travel close or over the Great Lakes
region Wednesday through the end week period. Passage of these lows
will result in a slight uptick in wind speeds and wave heights but
look to hold well below threshold values. Otherwise, return flow
from the departing high will lock easterly flow in place today
before turning more southwest to south late Wednesday into Thursday
following the passage of a warm front.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online
Area Forecast Discussion
National Weather Service Peachtree City GA
938 PM EDT Tue Mar 24 2020
Second round of convection pushing into north Georgia with
scattered showers and isolated thunderstorms expected to push
to the south and east across the area through early morning hours.
A Tornado watch remains in affect for portions of northwest
Georgia through 1 am. Only minor tweaks made to hourly
temperatures and winds this evening. Updated forecast products
.PREV DISCUSSION... /Issued 343 PM EDT Tue Mar 24 2020/
SHORT TERM /Rest of today through Wednesday Night/...
Main focus of fcst will largely be the strong to severe storm threat
in the near term and tonight period. An upper shortwave looks to
amplify some across the area late this afternoon into overnight.
While a lingering wedge has persisted in the northeast, mainly from
northern half of the Atlanta Metro over to Athens and northward, the
other portion of the CWA has had more destabilization with some
scattering of stratocu and increased daytime heating. The RAP even
has an axis of progged SBCAPE getting up to near 1500 J/kg going
into this evening ahead of the trough. With ample low and deep layer
shear expected, the Slight to Marginal severe outlook looks well
justified for damaging winds with any bowing segments, along with
hail and isolated tornado threats. The HREF probs for STP greater
than 1 do get above 90 percent for late afternoon into evening
across mainly western portions of the CWA, though any localized
interaction with the aforementioned wedge front could focus an
increased risk for stronger rotating convection and will need to be
Otherwise expecting a drying postfrontal regime for Wednesday and a
switch to NW flow aloft. Should still be pleasant above normal temps
getting into the 70s for most areas then lows in the upper 40s to
50s Wednesday night.
LONG TERM /Thursday through Tuesday/...
The highlights of the extended forecast are above average
temperatures with a couple dry days followed by a late weekend
The forecast picks up on Thursday morning with northwesterly mid-
/upper-level flow and a surface high sinking providing dry
conditions through Friday. South to southwesterly lower and upper
level flow returns on Saturday ahead of developing surface low over
the Midwest region. PoPs increase through the day Saturday into
Sunday as the associated cold front approaches and sweeps through
the CWA. Models have come into better alignment with the timing of
this system with some minor discrepancies in precipitation amounts,
ranging between .01 and .25 inches.
Medium range models bring in quasi-zonal flow with a weak surface
high over the Ohio River Valley on Monday then begin major to have
major disagreement through the rest of the extended forecast.
Currently, the GFS has the development of a faster and more
progressive mid-level over the Appalachians on Tuesday while the
ECMWF has a more amplified mid-level trough with a surface low
developing over the SE. Regardless, rain chances look to continue
into early next week even though confidence remains low on potential
High temperatures should remain above average through the period,
except on Sunday and Monday, thanks to the aforementioned cold
front. Lows should remain above average through the rest of the
AVIATION.../Issued 754 PM EDT Tue Mar 24 2020/
Mostly VFR across the TAF sites, with LIFR over areas east of ATL
including AHN. Expect a brief improvement over the LIFR area
ahead of the area of showers/isolated thunderstorms which should
move across the TAF sites 05-11Z. Northern sites
(ATL/RYY/PDK/FTY/AHN will drop to IFR after the storms move
through with improvement to MVFR/VFR between 12-15Z. CSG/MCN will
see MVFR with improvements after 14Z. Winds will shift from the SW
at 10kts with some gusts to NW at 5-10kts after 12Z.
//ATL Confidence...00Z Update...
Medium confidence all elements.
.PRELIMINARY POINT TEMPS/POPS...
Athens 60 58 74 51 / 50 80 20 5
Atlanta 78 60 72 52 / 100 80 20 5
Blairsville 60 52 65 46 / 90 90 30 5
Cartersville 68 58 71 49 / 30 90 20 5
Columbus 83 65 79 56 / 0 50 20 0
Gainesville 56 55 71 50 / 80 90 20 10
Macon 82 64 79 54 / 5 50 20 5
Rome 72 57 71 49 / 60 90 10 5
Peachtree City 82 60 74 51 / 30 80 20 0
Vidalia 83 68 82 57 / 0 30 30 5
Flash Flood Watch until 6 AM EDT Wednesday for the following
Tornado Watch until 1 AM EDT Wednesday for the following zones:
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
627 PM CDT Tue Mar 24 2020
.SHORT TERM...(This evening through Wednesday)
Issued at 307 PM CDT Tue Mar 24 2020
Aloft: Animation of WV imagery and RAP tropopause analyses showed
zonal flow over the CONUS. A fairly deep shrtwv trof was aprchg
the Pac NW coast. This trof will slowly migrate into the Wrn USA
thru tomorrow...but the flow downstream over NEB/KS will remain
zonal with just a touch of anticyclonic character.
Surface: 1000 mb low pres was near Lk Winnipeg with a sfc trof
extending S into Wrn NEB/KS. Its cool front extended back into MT.
The low will head NE to Hudson Bay thru tomorrow. Meanwhile...the
sfc trof will move into the CWA and weaken while the cool front
sinks thru the Nrn Plns tonight. By 00Z/Thu...the front will
stretch roughly W-E acrs Nrn NEB. A new lee low is also fcst to
form over Ern CO.
Tonight: Mostly clear. There could be some mid-lvl alctocu
floating thru after midnight. Temps will be mild...about 10F above
Low stratus remains over the E 1/4 of the CWA...where dwpts will
not mix out this afternoon like further W. This means some fog
will be psbl again late...but it won`t be as widespread as the
last 2 mornings.
Wed: Probably some fog to start E 1/4 of the CWA. Otherwise...
sunny and very warm. Widespread 60s/70s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 307 PM CDT Tue Mar 24 2020
Aloft: The GFS and EC ensemble means are indicating the the Wrn
USA trof will slowly advance thru the Wrn USA thru Fri...and then
cross NEB/KS Sat. There are some indications a closed mid-lvl low
could form as this trof passes by. Therefore...the flow aloft will
progressively become more SW. As has been the case for the last 4
months...the longwave trof will remain over the Wrn USA...with
the ridge over the E. Heights will recover some Sun as a shrtwv
ridge moves thru ahead of the next trof that is fcst to be moving
into the Desert SW. That trof will probably arrive here Mon.
Model assessment: The last 3 runs of the GFS-FV3/EC/CMC/UKMET are
tightly-clustered with minimal spread thru Sat...at least over
the CONUS. There are huge diffs upstream over the N Pac by that
time though...even with the last 2 EC runs! By Sun appreciable
diffs appear on the handling of the trof fcst to come out of the
Desert SW. The last 2 EC runs are deeper and slower with a closed
low forming...while the 06Z/12Z GFS-FV3 are open and faster. That
uncertainty will need to get ironed out before we can say much
about the sensible wx here next Mon. Fcst confidence is extremely
low beginning next Mon.
Surface: The cool front over Nrn NEB at 00Z/Thu will drop S thru
the CWA Wed eve and then stall acrs Srn KS thru Fri. Canadian
high pres will be to the N while svrl wk lows form and move E
along the front. The final and deepest low will eject SW-NE acrs
KS Fri night and into IA Sat. The 12Z EC/GFS-FV3 are very similar
on the track and intensity around 990 mb 12Z/Sat-00Z/Sun. If this
is correct...we may have a heavy/wet snow and wind problem on our
hands. With all the uncertainty referenced above...don`t want to
speculate much on next Sun-Tue.
Temps: The official fcst is near normal thru Sat...then above
normal Sun-Tue. However...both MOS and mdl 2m temps suggest
slightly cooler than normal Thu-Sat due to extensive cloud cover.
And if it snows Fri night into Sat...all bets are off for high
temps Sat. It could be 10-15 colder than what we`re currently
Precip: Nothing of significance expected before Fri. NBM (which
populates most of our POPs) looks way too high on precip chances
Thu night into Fri morning. Any precip in that time frame will
probably be drzl...if anything occurs at all. The way things are
looking now...steady rain will overspread the CWA Fri night and
change to snow before ending Sat. Typically...once snow starts
falling with systems of this strength...it doesn`t change back to
rain as the mdls are currently suggesting Sat afternoon.
Suggest everyone keep a close eye on the fcst Fri night into Sat
as things are currently looking threatening for
accumulating/plastering wet heavy snow and windy conds.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 622 PM CDT Tue Mar 24 2020
Main concern through the TAF period will be some low level wind
shear late tonight into Wednesday morning. Winds will increase in
the morning and turn toward the west or northwest as a front moves
through the terminals.
Issued at 307 PM CDT Tue Mar 24 2020
Confidence is high that near critical fire wx conds will occur
over the SW fringe of the CWA Wed afternoon. Confidence is medium
that critical conds could occur. Opted to post a Fire Wx Watch.
The main factor will be mixing heights. Deeper mixing could result
in lower RH and higher winds than are currently in the fcst. If
that occurs...a RFW will be needed.
NE...Fire Weather Watch Wednesday afternoon for NEZ082-083.
KS...Fire Weather Watch Wednesday afternoon for KSZ005-017.
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
706 PM CDT Tue Mar 24 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 300 PM CDT Tue Mar 24 2020
Main concern in the short term remains rain to snow potential
Wednesday into Wednesday night.
Radar showing last vestiges of showers exiting the northeast CWA
this afternoon. Trend in the HIRES models and less so the HRRR had
some redevelopment over eastern South Dakota this evening,
moving into west central MN. Some MUCAPE to 400 J/kg forecast to
move into that region well and an isolated thundershower possible
into the early evening far west central MN. Clouds will likely
linger over the area as well, with some fog possible later
Surface cold front progged to drop into central MN Wednesday
afternoon. Model trends continue to show fairly rapid rain/snow
changeover across central MN, most likely by Noon. Strong FGEN
develops along the boundary and we could see snowfall rates around
1 inch an hour if the column cools quick enough to generate wet
snow. Currently have 1-2 inches from southwest into central MN
with the higher totals where the transition occurs first over the
southwest. Will need to monitor tonights model run to see if the
cooling trend continues.
The snow exits to the east Wednesday evening, with perhaps some
wet snow accumulation on grassy areas around the metro.
.LONG TERM...(Thursday through Tuesday)
Issued at 300 PM CDT Tue Mar 24 2020
Following the Wednesday system, we work some weak high pressure
over the region for Thursday. Later Friday, we the next storm
system develop to the southwest and lift into the Central Plains
by Saturday morning. This should spread another precipitation
shield over the area Later Friday and lingering into Saturday. At
the moment, deterministic models have been trending wetter rather
than white. The 12z ECMWF was a bit slower and cooler eventually,
which should portend to the possibly of wet snow accumulation.
Still early to follow and model solution, especially on the
warmer Spring system. Will need to monitor trends the next few
Still looks like the overall temperature trend remains warmer
than normal through the period.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 706 PM CDT Tue Mar 24 2020
Complex period ahead with a front moving through tonight that
stalls out near the IA border Wednesday, when a surface low will
work across it, spreading a large shield of precip across the
area. For tonight, we will likely see scattered showers, and
possibly even a thunderstorm, work through with the front, though
confidence is low in coverage of showers along the front. Several
hi-res models show some clearing behind the front, with the
potential for dense fog forming, though this is a pretty low
confidence scenario. For Wednesday, rain arrives in the morning.
Trend from the HRRR, along with the RAP and 18z GFS/NAM is for a
warmer, more rain scenario tomorrow, along with precip likely
remaining southeast of AXN. In addition, we are seeing a slowing
trend with the timing.
KMSP...One trend we are seeing with the rain Wednesday is that it
is forecast to reach MSP a bit later, possibly not until the
afternoon. Low confidence with cig trends Wed morning as we could
see a period of VFR conditions behind the fropa before the main
precip shield arrives in the afternoon.
/OUTLOOK FOR KMSP/
Thu...MVFR cigs in mrng, bcmg VFR in aftn. Wind E 5 kts.
Fri...Chc MVFR cigs. Wind SW 5 kts.
Sat...MVFR/IFR with RA. Wind NE 15G25 kts.